## 1. Historical Overview


### 1.1 Descartes: Attention and Epistemology



In the early modern period a variety of explanatory roles were
assigned to attention by a number of different writers.
Descartes' *Meditations* provides one prominent example.
The result of Descartes' First Meditation--that everything
can be doubted--is in apparent tension with his Third
Meditation's claim that clear and distinct ideas are beyond
doubt. Descartes introduces a claim about attention to resolve this
apparent conflict. He says, in reply to the seventh set of objections,
that it is only when we pay attention to them that clear and distinct
ideas provide a place where doubt does not take hold:



> 
> So long as we attend to a truth which we perceive very clearly, we
> cannot doubt it. But when, as often happens, we are not attending to
> any truth in this way, then even though we remember that we have
> previously perceived many things clearly, nevertheless there will be
> nothing which we may not justly doubt so long as we do not know that
> whatever we clearly perceive is true. ('Replies to
> Objections', 309)
> 



This passage is usually cited for the point that it makes about
memory, but the picture that Descartes is here outlining is also one
in which attention has an important epistemic role to play: clarity
and distinctness realize their epistemic potential only when attention
is being paid to the ideas that have them. Those ideas can be doubted,
as, in accordance with the policy of the First Meditation they must
be, but that doubt cannot be maintained by a properly attentive
thinker. The crucial first move in Descartes'
epistemology--the move from radical doubt to certainty about the
truth of particular clear and distinct ideas--is, therefore, a
transition that is mediated by attention.


### 1.2 Berkeley: Attention and Abstraction



A quite different explanatory role is assigned to attention in Bishop
Berkeley's *Principles of Human Knowledge*, although here
again we find that it is in order to remove an epistemological glitch
that the notion of attention is brought in. In the Introduction to
*Principles of Human Knowledge* Berkeley rejects Locke's
claim that there exist such things as Abstract Ideas. But Berkeley
retains Locke's commitment to the core empiricist claim that the
thinking of thoughts is always a matter of handling ideas received
from experience. This would seem to lead to the conclusion that it is
not possible to think about abstractia, but Berkeley realizes that
that conclusion is unacceptable. It is, as he says, perfectly possible
to think about the properties of triangles in general.



In the second edition of the *Principles* Berkeley added a
couple of sentences to the Introduction that make it clear that it is
attention and, in particular, the withholding of attention, that is
supposed to explain the possibility of thinking about abstractia
without the need to postulate Abstract Ideas. These added sentences
tell us that:



> 
> [It] must be acknowledged that *a man may consider a figure merely
> as triangular, without attending to the particular qualities of the
> angles or relations of the sides*. So far he may abstract, but
> this will never prove that he can frame an abstract general,
> inconsistent idea of a triangle. (1710, Introduction to 2nd edn.
> SS16. emphasis added)
> 



In these sentences Berkeley is not attempting to elaborate a theory of
attention. He says nothing more about the idea that attention might
enable thought about abstractia. It is nonetheless clear that he
requires attention to play an important role in his picture of the
mind.



Berkeley's idea that attention and abstraction are linked was
taken up in the second half of the nineteenth century by William
Hamilton. Hamilton did not, however, think that the link between
attention and abstraction provided the starting point for an
explanation of attention, nor of abstraction. That is because he took
it that the relationship between the two phenomena was too intimate to
be explanatory. He writes that:



> 
> Attention and Abstraction are only the same process viewed in
> different relations. They are, as it were, the positive and negative
> poles of the same act. (1876, 88)
> 


### 1.3 Locke: Attention as a Mode of Thought



Descartes and Berkeley treat attention very briefly, but each assigns
attention to a particular explanatory role. Locke's treatment of
attention is also brief, but he has his own theory of the explanatory
role that attention plays, and goes further than either Descartes or
Berkeley in giving us a positive account of what attention is. His
account is given as part of the catalogue of 'Modes of
Thinking', which Locke sets out towards the beginning of Chapter
Nineteen of Book Two of the *Essay Concerning Human
Understanding:*



> 
> [W]hen ideas float in our mind without any reflection or regard of the
> understanding, it is that which the French call reverie; our language
> has scarce a name for it: *when the ideas that offer themselves
> (for, as I have observed in another place, whilst we are awake, there
> will always be a train of ideas succeeding one another in our minds)
> are taken notice of, and, as it were, registered in the memory, it is
> attention*: when the mind with great earnestness, and of choice,
> fixes its view on any idea, considers it on all sides, and will not be
> called off by the ordinary solicitation of other ideas, it is that we
> call "intention," or "study." (1689, II, 19
> SS1 emphasis added)
> 



In addition to providing these quick theories of
'reverie', 'attention' and 'intention or
study', the very same sentence of Locke's *Essay*
provides theories of 'remembrance',
'recollection', 'contemplation',
'sleep', 'dreaming', and
'ecstasy'. It is significant that Locke's account of
attention is given so briefly, and that it goes by as part of a crowd
of theories of these various other mental phenomena. Locke is not here
engaging in an uncharacteristically slapdash piece of rapid-fire
theorizing. His intention in going through this catalogue is to
establish that these are topics for which no new substantive theory is
needed. These are, in Locke's theory, simply 'modes of
thinking': 'reverie', 'study' etc. are
not names for independent phenomena, existing in their own right.
Instead they are the various names that thinking is given when it
takes place in various ways.



One consequence of Locke's treatment of attention as a mode of
thinking is that, once we have a theory of thinking before us, we need
no further theory to account for the possibility of attention,
contemplation, study, etc. (Just as, to use the classic example of
'modes', we need no substantive independent theory, once
we have a theory of walking, to explain the possibility of limping,
pacing or ambling.) We need to say *something* in giving an
analysis of the nature of modes, but--once the
thing-to-be-modified has been accounted for--our analysis can
simply say something brief, along the lines indicated by Locke. We do
not need to give a theory that postulates any substances or processes
specific to the explanation of attention.



Locke's modal view of attention has the consequence that no very
substantive theory of attention is needed once our theory of thinking
is in place. It also entails, and for the same reason, that attention
cannot figure in the explanation of how thinking itself is possible
(for any explanation in which it did figure would be analogous to an
explanation of walking that takes strolling to already be possible; it
would get its explanatory priorities backwards).


### 1.4 The Eighteenth and Nineteenth Centuries: Attention in Perception, in Action and in Reflective Thought



Locke viewed attention as an explanatorily slight phenomenon--a
mode of thought that is not in need of much explanation, nor capable
of providing much. Theories of attention moved away from that view
over the course of the eighteenth century. Attention was increasingly
treated as a phenomenon with explanatory work to do, and so as a
phenomenon for which a substantive independent theory needed to be
given. The attempt to provide such a theory got properly underway in
1738, when Christian Wolff's textbook on psychology was the
first to devote a whole chapter to the topic of attention (see
Hatfield, 1995, for an excellent discussion).



During this period the explanatory remit for theories of attention
broadened in two directions. The first move was away from the idea
that attention acts on already-received ideas and towards the idea
that attention is involved in the initial reception of those ideas.
Locke had characterized attention as the registration of
already-received ideas into memory. But by 1769, when Henry Home Kames
added the appendix of 'Terms Defined or Explained' to his
*Elements of Criticism*, attention's role as a regulator
of cognitive input was regarded as definitive of it:



> 
> Attention is that state of mind which prepares one to receive
> impressions. According to the degree of attention objects make a
> strong or weak impression. Attention is requisite even to the simple
> act of seeing. (1769, 18)
> 



As well as beginning to assign to attention a role in the explanation
of the reception of ideas, eighteenth century theories also moved
towards including a role for attention in the production of
*behaviour*. This is particularly clear in Dugald
Stewart's 1792 *Elements of the Philosophy of the Human
Mind*. Stewart retains Locke's view that attention has an
essential role to play in determining which things get stored in
memory. He adds to that view the claim that attention has a role in
determining which particular memories get recalled, writing that
"Some attention [is] necessary for any act of memory
whatever." (1792, 53). Stewart also claims that attention has a
role in the explanation of the development and deployment of at least
some skilled behaviours. The example that Stewart gives here is that
of "the dexterity of jugglers" which, he says,
"merits a greater degree of attention from philosophers than it
has yet attracted" (62).



In the century between Locke's *Essay* and
Stewart's *Elements*, then, attention ceases to be seen
merely as a certain mode of idea-handling, and comes to be seen as a
phenomenon in need of its own explanation, and with a role to play in
the explanation of perception, in the explanation of skilled action,
and in the explanation of memory (both in its storage and in its
recall).



In the century after Stewart's *Elements* the diversity
among the phenomena that attention was expected to explain continued
to grow, and it continued to include phenomena from across the
psychological spectrum from perception, to thought, to action. By the
end of the nineteenth century, in what was a crucial period in the
development of scientific psychology, there were some psychologists,
such as E.B. Titchener, who took the role of attention in perception
and in 'sensory clearness' to be its most essential
feature (see Titchener, 1908, 1910); others, such as Alexander Bain,
who thought that the essential feature of attention was its role in
action, (Bain, 1888); and a third group, of whom G.F. Stout was the
most prominent example, who argued that the primary job for a theory
of attention was to explain attention's role in reflective
thought (see Stout, 1891).



As a result of this diversity in their conceptions of
attention's explanatory remit (and as a result of the lack of
any established methodology for empirical psychology) the debates
between exponents of these various psychological theories of attention
got themselves into what was acknowledged to be a 'chaotic
state' (Pillsbury, 1906).


### 1.5 William James and His Contemporaries: Deflationary Theories



The diversity of explanatory roles assigned to attention in the
eighteenth and nineteenth centuries meant that theorizing about
attention at the end of the nineteenth century was in a chaotic state.
The ambition for theorists of attention writing at the end of the
nineteenth and the beginning of the twentieth centuries was to get
this chaos into order. The theories of attention proposed in this
period therefore tended to take the form of attempts to reveal
attention as something less mysterious and less complex than earlier
writers had supposed. This ambition to give a 'nothing
but...' reduction of attention can be seen in the most
influential work from this period: William James' *The
Principles of Psychology* (1890).



One aspect of James' approach is to play down the more complex
perceptual aspects of attention. His chapter on attention includes a
discussion of experiments into what we now call
'subitizing'--that is, into the ability to perceive
the cardinality of small stimulus sets without needing to count their
members--but James writes of these experiments that it "is
obvious that such observations decide nothing at all about our
attention, properly so called" (407).



Although James plays down attention's role in complex perceptual
phenomena, he does assign attention to an important explanatory role
in the production of behaviour. He claims, for example, that
'Volition is nothing but attention' (424). But when James
makes such claims it is as part of a general project that seeks always
to be deflationary where possible. When James associates attention
with volition it is as a way of suggesting how volition could be given
a deflationary treatment, not as a way of inflating attention's
explanatory role.



This deflationary approach to attention's explanatory remit
means that, when it comes to giving an account of the 'intimate
nature of the attention process', James can identify two fairly
simple processes which, he claims, 'probably coexist in all our
concrete attentive acts'. and which 'possibly form in
combination a complete reply' to the question of
attention's 'intimate nature' (1890, 411). The
processes that James identifies are:


1. The accommodation or adjustment of the sensory organs, and
2. The anticipatory preparation from within of the ideational centres
concerned with the object to which attention is paid. (411)



The first of these processes is reasonably familiar. By 'the
accommodation or adjustment of the sensory organs' James means
such processes as pointing one's ears in the right direction,
bringing one's eyes into focus, taking a sniff, and so on.



James's talk of 'anticipatory preparation' of
'ideation centres' is a little less clear, but the point
is again a quite straightforward one. What James has in mind here is
simply *imagination*. His claim is that when attention does not
involve adjusting one's sense organs it consists in imagining
the things or actions that one is attending to, or looking for.



James illustrates his claim about attention's link to
imagination with an example from Hermann von Helmholtz. This example
is an important one for James, and it illustrates some important
features of attention that subsequent theorists have tended to
neglect. The example involves the variety of attention that needs to
be paid when trying to discern the overtones in a note played on the
piano. Helmholtz asks us to sit at the piano and to play a G, then,
imagining the sound that we have just heard, to play a low C. Doing
this, it is claimed, enables one to hear that G is discernibly there
(as the third overtone) within the sound produced when C is played.
Helmholtz's claim, which James endorses, is that the kind of
attention that is paid when listening for an overtone is constituted
by the imagining of what that overtone would sound like. James goes
onto claim that there is a wide range of cases in which paying
attention to what one is doing consists in this same sort of
preparatory imaginative engagement.



Here, as in his more frequently discussed treatment of emotion, it is
distinctive of James's approach that he tries to account for a
large-scale personal-level psychological phenomenon in a realist but
somewhat revisionary way, so as to be able to give his account using
relatively simple and unmysterious explanatory resources. An
alternative deflationary approach--one which James explicitly
contrasted with his own--is the approach taken in 1886 by F.H.
Bradley.



Bradley advocated a view according to which attention is not the sort
of phenomenon for which an independent and substantive theory can or
needs to be given. Bradley does not develop this point in much detail,
and it is a point on which he would later change his mind, but in his
1886 article, 'Is there a special activity of attention?',
Bradley was concerned with arguing that a project such as
James's one of identifying particular processes as the
attention-constituting ones was wrongheaded. He claims that no
particular attention-processes can be identified since:



> 
> Any function whatever of the body or the mind will be active attention
> if it is prompted by an interest and brings about the result of our
> engrossment with its product. There is no primary act of attention,
> there is no specific act of attention, there is no one kind of act of
> attention at all. (1886, 316)
> 



Although Bradley does not use the Lockean vocabulary (and although
James himself does not seem to have taken Bradley in this way),
Bradley's position here has much in common with Locke's
claim that attention is a *mode*. Bradley's position,
like Locke's, is that what is essential to an instance of
attention is not the matter of *which* processes are taking
place, but the facts about *how* the things that happen happen.
He therefore takes the ennumeration of processes to be the wrong form
for a theory of attention to take.



Other writers who were contemporary with Bradley and James took
different approaches to the project of giving a deflationary
explanation of attention. In Theodule Ribot's 1888 book
*La Psychologie De L'Attention* the attempt to explain
attention took an approach that we would now classify as behaviourist.
In 1888 behaviourism had not yet been established as a general
approach in philosophical or psychological theories of the mind, but
Ribot's suggestion that attention's behavioural
manifestations are essential to it is nonetheless recognizable as an
early articulation of behaviourism in a strong form:



> 
> Are the movements of the face, the body, and the limbs and the
> respiratory modifications that accompany attention, simple effects,
> outward marks, as is usually supposed? Or are they, on the contrary,
> *the necessary conditions, the constituent elements, the
> indispensable factors of attention*? Without hesitation we accept
> the second thesis. (1888, 19)
> 



A somewhat more moderate version of this behaviour-centred approach
was taken by Alexander Bain, who identified attention, not with its
behavioural manifestations themselves, but with truncated versions of
the motor-control processes that typically bring about those
behavioural manifestations: processes 'stopping short of the
actual movement performed by the organ' (Bain, 1888, 371). Much
as Ribot's view can be seen as an early version of behaviourism,
Bain's view can be seen as an early version of the motor-based
approaches to attention that can be found in the literature of the
present century (see
 Section 2.8
 below).


### 1.6 The Twentieth Century: Locating Attention at a Bottleneck in Information Processing



The variety among the deflationary explanatory approaches that
characterized the theories of attention offered in the nineteenth
century gave way in the early twentieth century to a period in which
one such explanatory tactic was dominant: the tactic of behaviourism.
Behaviourists tended to neglect attention, but did not ignore it
entirely. John Dashiell's 1928 *Fundamentals of Objective
Psychology*, for example, is a behaviourist work that attempts to
account for attention "as a form of posturing" (Ch. 10,
SS3). The project of identifying a behaviour with which to explain
attention was, nonetheless, an understandably unpopular one. As
Gilbert Ryle notes, it is not only attention, but also 'heed
concepts' more generally, that resist simple behaviourist
analysis:



> 
> [W]hen a man is described as driving carefully, whistling with
> concentration or eating absent-mindedly the special character of his
> activity seem to elude the observer, the camera and the Dictaphone.
> Perhaps knitted brows, taciturnity and fixed gaze may be evidence of
> intentness; but these can be simulated, or they can be purely
> habitual. (1949, 133)
> 



In the middle of the twentieth century behaviourism's dominance
waned, cognitive psychology established itself, and a new theoretical
approach to the explanation of attention was developed. These three
developments were intimately related to one another. Instrumental to
all three was the publication in 1958 of Donald Broadbent's
*Perception and Communication*.



The year prior to *Perception and Communication*'s
publication had seen B.F. Skinner's attempt, in *Verbal
Behaviour* (1957), to apply a behaviourist explanatory approach to
distinctively human aspects of cognition. Skinner's project in
that book failed, and Noam Chomsky's famous 1959 review of the
book made its failure conspicuous. Chomsky's own work in
*Syntactic Structures* (1957) went some way towards
establishing the new cognitive paradigm for psychology by showing how
internal processing could be theorized by describing transformations
on representations in abstraction from the question of how those
representations were realized. Donald Broadbent's distinctive
contribution to the overthrow of behaviourism was to show how the move
from behavioural data to the postulation of a particular cognitive
architecture could be disciplined by the then-new strategy of
importing into psychology the intellectual resources used in thinking
about information technology. The year in which Broadbent's book
was published was an important year for the development of such
technologies, being the year in which (inter alia) the integrated
circuit chip was invented (see Mole, 2012). It was also the year in
which Subscriber Trunk Dialling was introduced to UK telephone
exchanges. The technology of the telephone exchange was what most
naturally suggested itself as a metaphor for attention at the time
when Broadbent was writing.



Towards the end of *Perception and Communication* Broadbent
explicitly sets out the claim that the theoretical resources developed
in thinking about the transmission of information through telephone
exchanges provide the basis for an alternative to behaviourism. He
also attacks the positivistic methodological principles that had given
many behaviourists their motivation. But the central lesson from
Broadbent's work, so far as the theory of attention goes, is a
lesson that he takes to be independent of this attack on behaviourism
and its positivist foundations. At an early stage in *Perception
and Communication* he remarks that:



> 
> Perhaps the point of permanent value which will remain in psychology
> if the fashion for communication theory wanes, will be the emphasis on
> problems of capacity. [...] The fact that any given channel has a
> limit is a matter of central importance to communication engineers,
> and it is correspondingly forced on the attention of psychologists who
> use their terms. (1958, 5)
> 



This introduction of the notion of capacity limitations into
discussions of perception and attention was, as Broadbent here
predicted, hugely and permanently influential.



Broadbent claimed not only that the human brain is subject to capacity
limitations of the sort that communications engineers had learnt to
theorize, he claimed also that these limitations are clustered so that
there is a single bottleneck in capacity that is especially critical
to the brain's handling of perceptual information. This
bottleneck was said to occur at the junction of two systems operating
in series, with the first system having a large capacity for
information processing, and operating automatically on all of the
stimuli with which the perceiving subject is presented, while the
second has a much smaller capacity, and therefore needs to be deployed
selectively.



Those who followed Broadbent took it that the bottleneck that results
from the connection of these two systems corresponds to attention in
the sense that, when a representation of a stimulus passes through
that bottleneck, the stimulus *ipso facto* counts as one to
which attention has been paid.



Broadbent himself was cautious about presenting his claims about
capacity-bottlenecks as a theory of attention. The word
'attention' occurs rarely in *Perception and
Communication*. Broadbent's later book, *Decision and
Stress* (1971), does describe his earlier experiments as
'studies of attention', but here too Broadbent prefers to
talk about 'selective perception' (chapter V) or
'vigilance' (chapters II and III). In an article from
1982, entitled, 'Task Combination and Selective Intake of
Information', he admits that: "The topic of this paper is
one that is often termed 'attention', and it may seem
unduly artificial to have given it a more cumbrous title." But
he goes on to reassert his qualms:



> 
> 'Attention' is a word in ordinary language, that can
> reasonably be used as a label for experiments in a particular area.
> Yet it has also been used as a theoretical concept, a mysterious asset
> or energy which is sometimes attached to human functions and sometimes
> not. This use of attention [...] is not very helpful, and
> avoiding the word in the title is a step towards clarity. (1982, 253)
> 



When Broadbent does use the word 'attention' it is mostly
in discussions of attention *shifting*. His view, at least in
his early work, seems to have been that where there is a bottleneck in
our information processing capacity there need to be additional
mechanisms that control how our limited capacity resources will be
deployed. These additional mechanisms of bottleneck-*control*
seem to have been what Broadbent thought of as the attention
mechanisms. He never took himself to have given a theory of them, only
to have given a theory of where they would be needed. Nor were these
mechanisms the topic that was at issue in the debates about attention
that Broadbent prompted. Those debates were concerned with questions
about the nature and location of the bottleneck itself, not about the
factors that determine what, on any particular occasion, gets to pass
through it.



In the decades following Broadbent a great many psychologists devoted
themselves to the task of locating the attentional bottleneck that he
had postulated. Almost all psychologists writing at this time were
guided to some degree by Broadbent's
two-serial-systems-and-a-bottleneck picture of perceptual processing.
The question of whether a given task is attention demanding was
therefore understood to depend on the question of whether the
performance of that task requires the engagement of the small-capacity
system that comes after the bottleneck of attention.  Research
into the attention-related demands of particular tasks therefore
became another route by which to approach the issue of where the
attentional bottleneck is located. Broadbent's
two-systems-and-a-bottleneck model was frequently questioned, but for
most research into attention in the second half of the twentieth
century it was very much the orthodox view. This has now changed. In
psychology's current paradigm, only a few aspects of
Broadbent's picture remain orthodox.


## 2. Theories of Attention


### 2.1 Capacity-Limitation Theories



Psychologists attempting to produce a theory of attention in the
nineteen sixties and seventies were highly influenced by Donald
Broadbent's picture of attention as corresponding to a
bottleneck in information processing capacity resulting from the
connection of two separate perceptual processing systems. The first
piece of business for these psychologists was to locate this
attentional bottleneck, by determining which sorts of processing are
done by the large capacity, pre-bottleneck system, and which by the
small capacity, post-bottleneck system. Debates between these
psychologists gave rise to various theories in which the selectivity
of attention was characterized with a claim about the location of this
bottleneck.


#### 2.1.1 Early Selection Theory



Broadbent's own account of the distribution of processing
between the pre-attentional system and the post-attentional system
defines the 'early selection' theory of attention. He
claimed that only very simple properties are detected by the large
capacity system, and that any semantic properties, or any properties
relating to the particular *identity* of a stimulus, are
detected only after representations of the stimulus have passed
through the attentional-bottleneck and into the smaller capacity
system.



The personal-level consequences of this early selection theory are
that we can recognize what things are and what they mean only if we
are paying attention to them, but can detect the simple physical
properties of things even when paying no attention to them. The theory
can be thought of as a communication-theoretic rendering of two
intuitive ideas, which Broadbent's own research had put on an
empirically sound footing. The first is that one has no immediate
control over one's awareness of simple features of one's
environment, such as the fact that there are people talking in the
next room. Whatever one is paying attention to, one will continue to
hear some chatter to be going on, if any is. The second idea is that
the details of things--such as the semantic content of that
chatter--can be detected only for the one or two things to which
one is paying attention: If one wants to know what the chatter is
about, one has to listen, and this involves disengaging one's
attention from other things that might be happening.



The early selection theory also entails, more problematically, that
the semantic properties of an unattended item must remain
unrepresented in the nervous system, and so entails that those
properties can have no psychological effects. According to this view
the semantic features of unattended items cannot explain why those
items attract attention to themselves, on the occasions when they do.
It was to this aspect of the theory that its opponents most frequently
objected.


#### 2.1.2 Late Selection Theory



The chief rivals of Broadbent's early selection theory were the
'late selectionists', who claimed that all (or almost all)
perceivable properties are detected automatically, by a large capacity
system that operates on all of the stimuli with which the perceiving
subject is presented. According to this late selection theory of
attention the consequences of passing through the bottleneck of
attention into the post-attentive small capacity system are only (1)
that the subject comes to be conscious of the contents that the large
capacity system has already succeeded in encoding and (2) that those
contents come to be stored in working memory (Deutsch and Deutsch,
1963).



Although it was originally proposed against the background of
Broadbent's now superseded theoretical framework, it would be
too quick to dismiss the late selection theory as an obsolete one. The
theory has much in common with some plausible and empirically
well-supported views found in the more recent literature. Jesse Prinz,
for example, shares the late selectionists' view that
attention's primary role is not in managing limited perceptual
processing resources, but in projecting already-processed
representations to working memory. Prinz's view, varying a theme
from the work of Stanislas Dehaene, is that this projection to working
memory is what makes it the case that the content represented comes to
conscious awareness. (Prinz, 2005, 2012, Dehaene *et al*.,
2006).



It should be noted that Prinz's main philosophical business is
with the explanation of *consciousness*. Objections have been
raised as to whether the process of projection to working
memory--which Prinz refers to as
'attention'--can adequately account for the various
things that attention does (Wu, 2014, SS6.3.2). If it cannot then
Prinz is willing to allow that this process is not the sole referent
of the English word 'attention', writing that 'other
researchers may choose to define attention differently', and
that 'those who disagree with my analysis of attention could
simply drop the term "attention"' (Prinz, 2012, p.
95).



The central component of the late-selection theory, as it was
originally understood, was that the effect of withdrawing attention
from a stimulus is to make it the case that that stimulus is processed
without the subject's awareness, rather than not being processed
at all. This component of the view has, to some extent, been
vindicated. The claim that unattended stimuli are subjected to some
processing of which the subject lacks awareness, including some
processing of those stimuli's semantic properties, is now
uncontroversial. Since we know that the semantic properties of
unattended stimuli can, for example, produce negative priming effects
(Tipper and Driver, 1988), we know that unattended stimuli are
processed in a way that allows at least some of their semantic
properties to be encoded. The semantic properties of unattended items
have such effects despite the fact that experimental participants are
typically unaware of what those properties are.



The traditional late selection theory is right in taking it that
inattention can lead to properties being encoded without our
awareness, rather than not being encoded at all, but that theory is
also committed to the claim that attention's *only*
effects are in determining what gets remembered and experienced, so
that the direction of attention has no effects on the initial
perceptual processing to which stimuli are subjected. These latter
claims we now know to be false. An important experiment by
O'Connor *et al*. used fMRI to compare neural activity in
participants who, in various task conditions, were presented with high
and low contrast checkerboard patterns in one or other half of their
visual field (O'Connor *et al*. 2002). In some conditions
these participants had to perform a task involving these checkerboard
patterns. In other conditions the patterns were irrelevant to the task
that the participants were performing (and in a third condition no
pattern was presented, but the participants were attending to the
screen in anticipation of a pattern that was about to be presented).
The results of these comparisons reveal that even in the first parts
of the neural circuitry through which information from the retina
passes, on its way to the visual cortex--even, that is, in the
Lateral Geniculate Nuclei--there is a difference in the baserate
of neural activity, and a difference in the response that stimuli
elicit, depending on what the participant is attending to. These
findings indicate that attention's effects are not limited to
cortical loci that are upstream from a late process of attentional
selection. They therefore refute any version of the late-selection
theory according to which the selectivity of attention is entirely a
'late process', occurring only after initial perceptual
encoding is complete.



The findings of O'Connor *et al*. create fewer problems
for some recent theories in which elements of the late selection view
are retained. Nilli Lavie and her collaborators have proposed one such
theory, which attempts to combine some aspects of the late selection
theory with some aspects of its early selectionist rival. According to
Lavie's 'load theory', attention *does*
correspond to a capacity bottleneck--much as Broadbent
thought--but the differing demands of the task that is at hand
lead to differences as to where that bottleneck restricts the
processing of a stimulus: in conditions where the processing demands
of perception are high the available resources will soon be exhausted,
and the bottleneck will operate at an early stage, with the result
that unattended stimuli will be processed rather little; in conditions
where the processing load of perception is lower the bottleneck will
operate at a later stage, with the result that unattended stimuli will
be processed rather more (Lavie & Tsal, 1994, Lavie *et
al*. 2004). This load theory predicts that peripheral stimuli will
elicit less neural activation, and will be less distracting, when the
subject's task is a perceptually demanding one. These
predictions have been borne out by behavioural and neurological
observations (Lavie, 2005).  The theory's theoretical apparatus
has also provided a useful framework for the philosophical treatment
of attention's relationship to consciousness (Hine, 2010). Many
psychologists nonetheless continue to be wary of Lavie's
rehabilitation of elements from the Broadbentian framework.



Other theories have been proposed that also retain the Broadbentian
idea that attentional selectivity is the result of capacity
limitations, while retreating further than Lavie from the picture of
attention that Broadbent introduced. These theories reject the terms
of the debate between early and late selectionists because they reject
the idea that the capacity limitations responsible for attention are
clustered into a single bottleneck. In some cases this is because the
selectivity of attention is taken to be the result of
*multiple* bottlenecks in processing capacity (see, e.g.,
Johnston and McCann, 2006). In other cases it is because these
theorists see capacity limitations as occurring throughout the
processing stream, and not as clustered into bottlenecks at all (see
Driver, 2001, for a suggestion along these lines, and Allport, Antonis
& Reynolds, 1972, for an earlier indication of it).


#### 2.1.3 Other Capacity-Limitation Theories



The early and late selection theories dominated discussions of
attention in the decades following Broadbent's seminal work, but
by the beginning of the nineteen nineties it had become clear that the
debate between advocates of the early selection theory and advocates
of the late selection theory had become fruitless. Those debates were
therefore thought to have been predicated on some sort of mistaken
assumption. Several different diagnoses have been proposed as to what
that mistaken assumption might have been. Little consensus has been
reached as to which of these diagnoses is correct, with the result
that some theorists--such as those discussed at the end of the
preceding section--retain ideas from the early and late selection
theories, while others regard this as a wrong-headedly retrograde
step.



One diagnosis is that the early/late debate was fruitless because the
terms 'early' and 'late' are themselves
problematic. If perceptual processing occurs in a parallel processing
architecture without any prevailing direction of information flow then
there can be no sense in labeling one part of that architecture as
earlier or later than any other. If the attentional bottleneck is
located in a system that has such an architecture then it may be this
that explains why there was no satisfactory answer to the question of
whether attentional selection is early or late. It seems to have been
with this thought in mind that some writers have suggested that the
failure of the debate between early and late selection theories was
owing to the fact that that debate requires us to make an assumption
about the *linearity* of the processing stream in which
selection occurs (see, e.g., Prinz and Hommel, 2002, 3). This is a
thought that needs to be treated with care.



The claim that it was a problematic assumption about linearity that
led the early/late selection debate into fruitlessness received its
most influential treatment in an important paper by Alan Allport
(Allport, 1992). Allport identifies several problematic assumptions
that the early/late selection debate requires. His characterization of
what he takes to be the problematic assumption about linearity is as
the claim that:



> 
> [T]he processing of nonsemantic attributes (i.e. the processing of
> attributes other than symbolic or categorical identity) occurs earlier
> in a logical/causal sequence of operations than does any semantic or
> categorical processing. (1992, 187)
> 



Despite Allport's qualms, this assumption about linearity does not
seem, on the face of it, to be a problematic one. There is nothing to
be objected to in the claim that the situations in which we encounter
a written word and come to be in a position to know what that word
means are typically situations in which our sensory transducers
respond firstly to simple nonsemantic properties of the word. In order
for creatures like us to detect the semantic properties of written
words, it *is* necessary for our information processing systems
to first encode some information about the simple spatial properties
of the lines on the page. This information does then get passed on to
subsequent processing stages in which more complex properties,
concerned with semantics and stimulus identity, get processed. If this
sort of linearity is what Allport was taking issue with then it seems
he must have been mistaken, since there is nothing problematic about
the idea that there is this much linearity in the processing to which
stimuli are subjected.



Nor is there anything unscientific about that idea. It continues to be
entirely normal for neuroscientists to refer to the processing that
takes place in occipital brain areas as 'early' and the
processing in frontal areas as 'late'. Such thinking can
be seen in a much-cited review of neuroimaging work on attention, in
which Sabine Kastner and Leslie Ungerleider speak of:



> 
> ... an increase in the complexity of processing as activity
> proceeds anteriorly through the ventral stream into the temporal lobe.
> Whereas posterior regions in cortex are preferentially activated
> during the processing of object attributes, such as colors or
> scrambled objects and faces, more anterior regions are activated
> selectively during the processing of intact objects and faces. (2000,
> 319)
> 



The orthodox view, expressed here by Kastner and Ungerleider, is
subject to differing interpretations. Those who believe that
perception and cognition are best thought of as arising from a
hierarchical Bayesian process might reject the idea that information
progresses through the nervous system in a bottom-up fashion, with the
detection of simple properties happening at an early stage, and the
detection of more complex properties happening at a later one. Current
advocates of such hierarchical Bayesian theories place great emphasis
on the idea that the prior hypotheses required by a Bayesian inference
can be generated in a top-down fashion, and can then be tested against
incoming signals which contain information only about the ways in
which the predictions generated by those hypotheses are in error
(Hohwy, 2013). Such theories break from the tradition of thinking
about the information flow in the brain as being largely one-way, but
they retain the idea that information is organized into a structure
with earlier and later stages, with these stages now being understood
as corresponding to the more or less abstract layers in an
hierarchically organized Bayesian inference. They therefore retain the
idea that there are earlier and later stages in the processing of any
given stimulus, while rejecting the idea that there is one predominant
direction of information flow in the brain. Since this much linearity
remains in our current thinking about the architecture of perceptual
processing, we cannot coherently blame an assumption about this much
linearity for the troubles that led to the fruitlessness of the debate
between early and late selectionists.



That is not to say that the early/late selection debate was entirely
free of problematic assumptions relating to linearity--only that
psychology has not yet settled upon a satisfactory account of the way
in which assumptions about linearity led the early/late debate into
trouble.



A reason why assumptions about linearity may have been problematic is
that when, following Broadbent, we think about hierarchical perceptual
processing *while bearing in mind the communications
engineer's concerns about capacity limitations*, it then
becomes natural to make some additional assumptions about the way in
which this hierarchically organized architecture supports
personal-level cognition. The early/late debate's problems are
more plausibly blamed on these additional assumptions, rather than on
any assumptions about linear or hierarchical organization *per
se*. Given that some physical properties of a thing must first be
represented in order for a person to become aware of that thing's
semantic properties, it is natural for the communications engineer to
suppose that no further representation of these physical properties
needs to be generated in order for that person to also be aware of
those properties, so that a person who is experiencing the semantic
properties of a stimulus must have been through a process that already
gives them an experience of that stimulus's simple spatial
properties. This additional supposition would be a mistake, since the
brain represents the physical properties of stimuli in multiple,
parallel, somewhat overlapping systems, only some of which put the
subject in a position to think about the properties that they
represent. In order to get to a representation of the meaning of the
word on a page, the subject's brain must represent that
word's physical properties, but it turns out that the
brain's representation of these physical properties need not put
this perceiver in a position to form thoughts about them. Their access
to these properties might require that the properties be represented
all over again, in some parallel system. From the point of view
introduced by Broadbent - that of a communications engineer who
is concerned with the management of limited capacity channels -
this seems strangely profligate. At least some of the problems with
the early/late debate can be attributed to this: not an assumption
about linearity *per se*, but an assumption about the linearity
of the processes that support personal level thinking.



Once the problematic assumption about linearity has been made precise,
however, we see that it cannot be satisfactory to credit the entire
collapse of the early/late debate to this assumption. The falsity of
the assumption about the linearity of the processes supporting
personal-level awareness does not undermine the very idea that the
early/late debate is a meaningful one. The problems that it creates
are largely methodological. The falsity of that assumption means that
one cannot make an inference from a lack of personal-level awareness
of some content to the absence of representations encoding that
content. It also means that Broadbent was wrong to suppose that the
psychological effects of unattended stimuli can only depend on those
properties of which the inattentive perceiver can be aware. But these
are methodological problems. They do not, by themselves, imply that
the debate between the early selection theory and the late selection
theory must have been misconceived.



The situation that we find ourselves in is, then, a somewhat unhappy
one. Everybody agrees that there was something misconceived about the
debate between the two theories of attention that dominated the
decades following Broadbent's reintroduction of attention to the
psychological agenda. The ongoing influence of Broadbent's
selection theory, and of the early/late debate, has often been noted,
and sometimes lamented (Driver, 2001, 56). But nobody is clear about
whether the elements of those theories that are retained in current
theorizing are problematic ones.


### 2.2 Feature Integration Theory



In the early nineteen eighties, Anne Treisman and her collaborators
identified the existence of 'the binding problem', and
described a process that could solve that problem. Treisman proposed
that attention be identified with this process. This proposal is known
as the Feature Integration Theory of attention. It has been hugely
influential, not only as a theory of attention, but also as the
framework that introduced and regimented research into the
independently interesting question of the binding problem (for more on
which, see
 'The Unity of Consciousness'
 esp.
 SS2.2).



Treisman describes the way in which the binding problem arises like
this:



> 
> Sensory information arrives in parallel as a variety of heterogeneous
> hints, (shapes, colors, motions, smells and sounds) encoded in partly
> modular systems. Typically many objects are present at once. The
> result is an urgent case of what has been labelled the binding
> problem. We must collect the hints, bind them into the right spatial
> and temporal bundles, and then interpret them to specify their real
> world origins. (2003, 97)
> 



We can illustrate this problem with an example. Suppose we have a
subject who is presented, at one time, with a red tomato and a green
apple. This visual input is, Treisman says, initially broken up for
specialized distributed processing--so that, for example, one
part of the brain is responsible for detecting the shapes of things, a
different part is responsible for detecting their colours. The
shape-detecting centres represent the fact that a tomato-shaped thing
is present, and they represent the fact that an apple-shaped thing is
present. The colour-detecting centres represent the fact that a red
thing is present, and the fact that a green thing is present. But the
subject, if he is a normal human, knows more than is implied by these
four facts: He knows that the red thing is the tomato-shaped thing and
the green thing the apple-shaped thing. To know this he must have a
way of 'binding' the representation of red in the colour
centre with the representation of the tomato shape in the shape
centre. The binding problem is the problem of knowing how to put
together the properties that have been detected in separate
specialized detection centres.



Treisman's proposed solution exploits the fact that
*spatial* representations are ubiquitous, and the idea that
there is only one thing to be seen in any one place at any one time.
If the centre for detecting colours detects red *at place one*
and green *at place two*, and if the centre for detecting shape
detects a tomato shape *at place one* and an apple shape *at
place two*, then, given the principle that there is a maximum of
one visible object per place per time, the binding problem can be
solved. Treisman therefore proposes that we achieve a correctly bound
representation by moving a variously sized 'window' from
one location in the perceptual scene to another. This window blocks
out the information from all but a single location, and all the
features found at that location can then be 'bound' as
being features of the same object. The area covered by the window
within which features are bound is taken to correspond to the region
to which attention is being paid.



There is more than one way to understand the explanatory import of
Treisman's claim that the window of attention corresponds to the
window within which features are bound. Treisman's early work
presents that claim as an attempt to identify the processes of
attention (by telling us that they are the processes of feature
integration). In her later work the explanation being offered is no
longer simply one in which it is attention that occupies the role of
explanandum and binding processes that occupy the role of explanans.
Her later claim is that solving the binding problem is one role for
the kind of selectivity that attention enables.



There is some work in which the Feature Integration Theory has been
pressed into the service of more ambitious explanatory goals. That
theory plays an important role in John Campbell's 2002 attempt,
in *Reference and Consciousness*, to use attention to explain
how the reference of demonstrative expressions gets fixed by their
producers, and understood by their consumers (see section
 3.2).
 Treisman herself suggests, albeit tentatively, that descendants of
the Feature Integration Theory may provide part of the explanation for
"the bound, unitary, interpreted, personal view of the world of
subjective experience" (Treisman, 2003, 111). She goes on to
suggest, again tentatively, that the sort of explanation that such a
theory provides "should give us all the information there is
about the conditions that create consciousness" (*op
cit*).



Opposed to those who think that a theory of feature binding will be a
large component in our theory of attention, of the unity of
consciousness, or of anything else, are a number of philosophers (and
a smaller number of psychologists) who deny that feature binding
creates a problem that needs any serious cognitive apparatus for its
solution. Such claims have been made for a variety of reasons. They
are generally made as part of large-scale revisionary proposals for
the conceptual framework of cognitive neuroscience. Kevin
O'Regan and Alva Noe's rejection of the binding
problem 'as, in essence, a pseudo-problem' (O'Regan
and Noe, 2001, 967) comes as part of their general attack on the
idea that perception requires the representation of the thing
perceived. Vincent Di Lollo has suggested that the assumptions about
neural coding that generate the binding problem have been superseded,
with the result that the binding problem is an ill-defined one (Di
Lollo, 2012). And M.R. Bennett and P.M.S. Hacker, in their book-length
critique of the philosophical foundations of neuroscience, claim that
the notions of representation and information that enjoy currency in
neuroscience are subject to various confusions, and that these
confusions lead to it being 'widespread' for
neuroscientists to make "confused statements of the so-called
binding problem" (Bennett and Hacker, 2003, 14). These debates
about the status of the binding problem (reviewed by Plate, 2007) turn
on foundational issues for the cognitive sciences generally. They have
ceased to be specifically concerned with the explanation of
attention.



Even if these philosophical critics of the binding problem are right
to suggest that a perceiver can typically experience several
properties as belonging to a single object without the need for any
special binding process to integrate the representations of those
properties, it may nonetheless be true that, in some particular cases,
attention does play a role in determining the way in which different
streams of sensory information come to be combined. Even in these
circumscribed cases, the question of how this binding-like role for
attention should be characterized may raise its own philosophical
difficulties. Several psychologists studying the integration of
information from across different sensory modalities have found
themselves running into such difficulties, claiming that the role of
attention in integrated multisensory perception is
'curious', and 'a paradox', especially in
cases that involve the perception of speech (Tiippana, Andersen and
Sams, 2004; Macaluso *et al.*, 2016). Philosophers who have
interrogated the assumptions leading to the idea there is a general
binding problem have not yet extended their critique to these more
specific cases. A preliminary philosophical examination suggests that
these may be cases in which the appearance of paradox derives from
certain questionable assumptions about the predominantly bottom-up
nature of perceptual processing, or from assumptions of a more
metaphysical sort, concerning the localizable way in which
attention's causal influence is exerted (Mole, 2020).


### 2.3 Coherence Theories



The view that the function of attention is the management of
limitations in the brain's information processing capacity has
been an orthodox one among psychologists since Donald Broadbent
introduced it in the nineteen fifties, but it has sometimes been
called into question. The theories of attention proposed by
philosophers have tended not to endorse any straightforward version of
the capacity-limitation view, and there are empirical reasons to think
that the simplest versions of such a view are mistaken. In the
nineteen seventies Ulric Neisser and his collaborators carried out a
series of experiments showing that, when appropriately trained, a
subject can perform two attention-involving tasks concurrently,
without much interference between them (Hirst *et al*., 1980,
Neisser, 1976). Neisser interpreted these experiments as suggesting
that, insofar as there is a bottleneck that attention is needed to
manage, it must often be a bottleneck in behavioural coordination,
rather than in information processing capacity. Simple bodily
limitations are what prevent us from looking in two directions at one
time, or from throwing a ball and writing with the same hand.
Neisser's suggestion was that in many cases cognitive processing
was selective, not as a result of limitations in processing capacity,
but only in so far as such bodily limitations required it to be.



In two papers from 1987, authored individually but published in the
same volume, Odmar Neumann and Alan Allport developed a similar idea.
Whereas Neisser emphasized the constraints that are imposed on
cognition by the need to manage a single body, Neumann and Allport
both emphasized the constraints that are placed on cognition by the
need to maintain a coherent course of goal-directed action. They
describe their position as a 'selection-for-action'
theory.



If we think of 'action' as here referring to bodily
behaviour then the selection-for-action theory is very similar to
Neisser's view. But Neumann and Allport's point retains
its force if we extend the notion of action to include deliberate
mental activities, such as puzzle-solving, for which no bodily
limitations are in play. There is here an "analogy between
practical and theoretical and activity", which was noted in an
1891 paper by G. F. Stout:



> 
> Thinking is action directed towards intellectual ends. Intellectual
> ends are attained by an appropriate combination of movements of
> attention just as practical ends are attained by an appropriate
> combination of movements of the body. If, therefore, we desire to
> explain the process of Thinking, we must clearly determine the nature
> of active Attention. (Stout, 1891, p. 23)
> 



As Stout and the later generations of action-oriented theorists
indicate, the need to select among several possible sources of
information, and to select among several possible things that might be
done with the information that has then been selected, is a
characteristic of almost all deliberately executed thoughts and
actions, whether those actions are bodily or intellectual. This
ubiquitous need for selectivity has been emphasized in a series of
works by Wayne Wu, where it is referred to as the "many many
problem"(Wu, 2011a, 2014, 2019).



In Wu's handling of it, the idea that Neumann and Allport
emphasized becomes part of a larger attempt to understand the
essential connections between attention and agency (Wu, 2011b). For
Wu, attention's role in action is more fundamental than its role
in perception. Stout is not the only precedent for this idea. The same
connection was noted by William James when he claimed that
"Volition is nothing but attention", (see Section
 1.5,
 above). As with these earlier authors, Wu's point is not just
that, by treating attention as a purely perceptual phenomenon, we
ignore many of its other instances. Instead Wu wants to suggest that
any division we might attempt to draw between perceptual attention and
the attentional selectivity required by agency would be an artificial
one. Even the involuntary capture of attention by perceptually salient
stimuli should, Wu thinks, be understood as involving a kind of
readiness to act on the things to which we involuntarily attend
(*op cit*, SS3). Wu's selection-for-action theory of
attention is therefore intended as a step towards a unification of our
philosophical account of ourselves as agents and our philosophical
account of ourselves as perceivers.



According to selection-for-action type views, the function of
attention is not the management of capacity limitations. It is,
instead, the management of capacity *excess*. It is because we
can process multiple stimuli that we can be distracted by them, and
because we can be distracted by them, not because we cannot process
them, that we need mechanisms of attention to provide selectivity and
focus. Attention, on this view, serves to lend coherence to, and to
prevent interference between, the activity of several components in a
system that has the capacity to handle far more stimuli than those
pertaining to the subject's current task. Such a view contrasts
sharply with Broadbent's conception of attentional selectivity
as capacity-bottleneck management.


### 2.4 General-Purpose Prioritization



In the tradition perpetuated by Wu, the selectivity of attention is
understood as providing a solution to one particular problem, created
by the fact that there are multiple courses of action that might be
taken at any time, with the taking of any one requiring the others to
be suppressed. The solving of this particular problem is not the only
cognitive need that could be served by an operation of selectivity,
even in a mind without bottlenecks of processing capacity. The
selection-for-action theory is therefore not the only alternative to
Broadbent's bottleneck theory. Other functions for attentional
selectivity might also be proposed. Alternatively--rather than
electing any one of these functions of cognitive selectivity as being
the function that is essentially served by attention--we might
instead characterize attention as a quite general process of
selectivity, recruitable on any of the various occasions when one
thing needs to prioritized over another, whether this prioritization
is required by the presence of a processing bottleneck, required in
order for a coherent action-plan to be executed, or required for some
quite different reason. The work of Sebastian Watzl develops the idea
that attention might be such a non-specific process of prioritization
(Watzl, 2017).



In Watzl's treatment of it, this idea places particular emphasis
on the fact that, just as a binary 'is greater than'
relation can introduce a partial ordering on a set, so a number of
these binary prioritizations can be considered in sum, as introducing
a prioritization structure on the several items that together
constitute one's mental life. For Watzl, attention is the
process by which one's life comes to have such a structure.



Watzl also claims that any mind which lacked such a structure would
therefore be lacking a particular perspective on the world, and so
would not be the mind of a creature with the subjective point of view
that is characteristic of conscious experiences. From this he derives
the claim that every conscious creature is attentive. Carolyn Jennings
has suggested that certain kinds of highly engaged expert performance
may be a counterexample to this (Jennings, 2015).


### 2.5 Precision Optimization Theories and Prediction Error Coding



The idea that there might be reasons for attentional selection that
have nothing to do with processing bottlenecks has also been a theme
in the work of psychologists hoping to understand perception as a
process of Bayesian inference (Friston *et al*. 2006,
Summerfield & Egner, 2013), and in the work of those philosophers
who have been influenced by them (Hohwy, 2013; Clark, 2013, 2017).



In what has come to be the most philosophically developed version of
this Bayesian approach to the mind (Hohwy, 2013, Clark, 2013),
cognition as a whole is understood to be a process of Bayesian
updating, in which a hierarchically-organized series of hypotheses is
constantly being tested, with each hypothesis being updated in the
light of evidence coming from the level below. Advocates of this
theory attempt to find room within this hierarchical framework for all
aspects of cognition, including perception, thought, and action. A
central claim of their theory is that the information that gets passed
up through this hierarchy is encoded in the form of signals
representing the *errors* in the predictions that have been
made by hypotheses at the hierarchy's next level up, with the
content of one's experience at any time being given by whichever
hypothesis makes the least erroneous predictions. (Different versions
of the theory use different techniques to calculate the relative size
of these prediction errors.) Given their commitment to
prediction-error coding, a central claim of these theories is that the
role of our sensory encounter with the world is to provide information
about the way in which our prior hypotheses get things wrong: instead
of providing us with the information that it has started to rain, our
senses provide only the information that it is more rainy than we had
expected.



Advocates of this theory claim that it "allows us to see
attention in a new light and to provide alternative conceptualizations
of its functional role in our overall mental economy" (Hohwy,
2014, p. 191). According to these 'alternative
conceptions', attention adjusts the weighting of incoming
prediction error signals, in accordance with their expected
*precision* (Hohwy, 2012). 'Precision' is to be
understood here in the sense that contrasts precision with accuracy.
'Accuracy', in the intended sense, is a measure of the
difference between the value indicated by a signal and the actual
value, whereas 'precision' is a measure of the random
fluctuation in that signal, even when the actual input is held
constant. A miscalibrated instrument might, in this sense, be highly
precise, without being especially accurate.



Various empirical results make it plausible that the brain takes
account of expected precisions when it is processing perceptual
signals. In the ventriloquist illusion, for example, it is plausible
that expectations of precision have a role to play: It is because
vision is expected to give a more precise indication of location than
audition that sounds are heard to come from the location where their
source is apparently seen. Other considerations make it equally
plausible that attention plays a role in accommodating the variations
in these expected precisions, as we move from one context to another.
If we expect that the signal from vision is likely to be a noisy
one--perhaps because a thick fog has started to
descend--then we may place more weight than usual on the
information that is present in the signal coming from audition. It
seems likely that there is a role for attention in bringing about this
change of weighting. It is more controversial to claim, as the
advocates of this theory do, that "attention is nothing but
precision optimization in hierarchical inference." (Hohwy, 1014,
p.244, citing Feldman & Friston, 2010). Ransom *et al*.
have suggested that, by taking attention *always* to be
precision optimization, this theory struggles to account for certain
forms of voluntary attention (Ransom *et al*. 2017). Clark has
suggested that this challenge can be met if the sources of voluntary
attention are identified with beliefs, rather than desires (Clark,
2017).


### 2.6 Competition Theories and Cognitive Unison



Like the precision-optimization theories that have been advocated by
Hohwy and Clark, from within the framework of the prediction-error
coding theory, the Coherence theories advocated by Neisser, Neumann,
Allport, and Wu have also suggested functions for attention other than
the management of limitations in processing capacity. Despite the
availability of these non-Broadbentian conceptions of
attention's function, the Broadbentian idea that
attention's selectivity serves to manage limitations in
processing capacity continues to be regarded by many psychologists as
incontrovertible. The claim that "Because the visual system does
not have the capacity to process all inputs simultaneously, there must
exist attentional processes that help the visual system select some
inputs" continues to be treated as a platitude of the sort that
can be used as an uncontroversial opening sentence when introducing
one's research. (The example just given comes from the beginning
of Vecera (2000), but many more examples of the same claim can easily
be found.)



For those who reject this platitude, and think that the
*function* of attention is something other than the management
of limitations in processing capacity, it is natural to think that the
*mechanisms* of attentional selection may be something other
than capacity bottlenecks.



The clearest non-bottleneck mechanisms for achieving selectivity are
*competitions*. Since well-organized competitions can always
select one winner, however good and however numerous the competitors,
the selectivity of a competitive mechanism need not have anything to
do with bottlenecks, or with any other limitations of processing
capacity.



Competition-based mechanisms for achieving selectivity come in at
least two varieties: In a simple *race* mechanism each of the
competitors independently completes a process that is comparable,
along some dimension of variation, with the processes that are
completed by each of the other competitors. The competitor that
achieves the highest value on the relevant dimension of variation is
selected as the winner. In a *struggle* the competitors do not
just get on with their own processing in the hope that they will do it
better than each of the other competitors. Instead the active
suppression of other competitors is a part of the process that each
competitor carries out. Simple race models of attention have been
proposed (Shibuya and Bundesen, 1988, Bundesen, 1987), but our best
current theories supplement the simple race mechanism with some
components of mutual struggle, or with additional processes of
top-down control (see, for example, Bundesen and Habekost, 2008).



One suggestion for a supplemented-competition mechanism for
attentional selectivity is the biased-competition model, elaborated in
several works by Robert Desimone, John Duncan and John Reynolds. The
biased-competition model accounts for various attention-involving
effects, at the personal and at the sub-personal level, as being
effects that arise from numerous struggles between the different
stimuli that fall within the variously sized receptive fields of
neurons throughout the perceptual processing hierarchy. It is
hypothesized that each one of these struggles is biased, although not
settled outright, by a top-down attention-specific signal (Desimone
and Duncan, 1995, Reynolds and Desimone, 2001).



We have said that competitions are selective in ways that do not
involve limitations in capacity, and that competition-based theories
of attention's underlying mechanisms are therefore natural
accompaniments to selection-for-action type views of attention's
function (Section
 2.3),
 and perhaps to other views that involve a break from the Broadbentian
view according to which attention's function is the management of
capacity limitations. Competition views of attention's
mechanisms do not, however, require us to take a non-Broadbentian view
of attention's function. Although the biased competition view
sits naturally with a non-Broadbentian view of that function, Reynolds
and Desimone continue to introduce the biased competition theory as an
attempt to understand attention in recognizably Broadbentian terms,
writing that:



> 
> The visual system is limited in its capacity to process information.
> However, it is equipped to overcome this constraint because it can
> direct this limited capacity channel to locations or objects of
> interest. (2001, 233)
> 



Some advocates of the biased competition view emphasize the particular
importance of the top-down biasing signals that the theory postulates
(e.g., Beck and Kastner, 2009, p. 1156), taking the *source* of
these signals to be the true locus of attentional selection. Others
suggest that the biased competition theory is better understood as a
theory that refuses to identify any such locus, and that it should
instead be read (as suggested in Duncan's original presentation
of the theory, (Duncan 1996)) as attributing the selectivity of
attention to the totality of an integrated competition, involving
processes of various sorts at various levels, any part of which can
bias any other (Mole, 2011, SS6.7, 2015).



When it is understood in this second way the biased-competition theory
accords with the proposal that attention should be taken to have a
metaphysical status analogous to that of unison in an orchestra.
According to this view it is always a mistake to identify any one
process as the attention process (or any set of processes as the
attention processes); attention requires the unified activity of
whichever processes happen to be relevant to a person's current
task, but, since these vary from one task to the next, it does not
require any *particular* processes to be taking place. Such a
view has been developed in work by Christopher Mole, who dubs it the
'Cognitive Unison Theory'. Metaphysically speaking, such a
theory can be understood as a revival of John Locke and F.H.
Bradley's view that attention is a mode of thinking (see
 Section 1.3
 above). Phenomenologically the view has a precedent in Ribot's
suggestion that attention be identified with 'monoideism'
(Ribot, 1889, p. 10). It also draws on some ideas about the
'polymorphousness' of attention, which were advocated in a
1964 monograph by Alan White, on the basis of considerations drawn
from the examination of various 'heed concepts' in natural
language.



Because operating in unison requires an absence of task-irrelevant
processing, the most straightforward version of the unison theory
entails that full attention is a rare achievement, with most cases of
attentiveness involving what is, strictly speaking, only partial or
divided attention. Mole (like Ribot) accepts this implication. Yair
Levy has suggested that doing so prevents him from giving an adequate
account of phenomena such a listening, or observing, which always
require some attention to be paid, but which can nonetheless be done
more or less attentively (Levy, 2019). Work by Philipp Koralus has
suggested that a more satisfactory treatment of divided attention can
be given if the attentive pursuit of a task is understood to share
certain formal properties with the answering of a question (Koralus,
2014). This characterization of attention as "the means by which
we answer questions about the environment" has been argued for
on phenomenological and epistemological grounds by Naomi Eilan (Eilan,
1998). (Eilan credits the thought to Rowland Stout, whose treatment of
it can be found in Chapter 9 SS5 of Stout 2006.) Koralus draws on
Hamblin's 1958 semantics of questions to provide a formal model
of such questioning (Hamblin, 1958).



There are philosophical issues, independent of the cognitive unison
theory, about the way in which partial or divided attention relates to
full attention, and about whether a distinction should be drawn
between the attention that is given to things by which we are merely
distracted and the attention that is given to things on which we
remain concertedly focused. Aaron Henry considers these questions as
part of a more general enquiry into attention and control, using the
notion of constitutive norms to provide an account in which
distraction always does involve a certain sort of shortcoming, while
nonetheless qualifying as a case of genuine attention, rather than
merely being a defective approximation of it (Henry, 2019). Zachary
Irving has suggested that the wandering of a distracted mind presents
philosophical puzzles of its own, and has worked towards giving an
empirically-informed account of mind-wandering that avoids these
puzzles. His account takes such wandering to be attentive but unguided
(Irving, 2016). Theories such as the Cognitive Unison Theory, in which
attention essentially depends on the performance of an
understanding-guided task, will need to find some alternative account
of the phenomena that Irving identifies.


### 2.7 Spotlight Theories



Whereas *bottleneck* metaphors have traditionally guided the
theories that attempt to locate the cognitive resources that operate
only on attended stimuli, it has been *spotlight* metaphors
that have guided the theories that attempt to say which features of a
stimulus determine whether attention is being paid to that stimulus at
any given moment (e.g., Watchel, 1967; Woodman and Luck, 1999; see
Fernandez-Duque and Johnson, 2002, for discussion). The idea suggested
by the spotlight metaphor is that a stimulus's *location*
ultimately determines whether or not that stimulus receives attention:
the point here is not to deny that one can pay attention to something
on account of it being brightly coloured, or on account of it being
interesting. The point is, instead, that one pays attention to
brightly coloured or interesting things only by directing one's
attention to the location of those things.



One can easily see why the spotlight metaphor has been appealing. If
we are presented with an array of differently coloured shapes,
appearing and disappearing in various places, then there will be any
number of attention-demanding tasks that we might perform regarding
that array. Some tasks might require us to attend to whatever is going
on at the top of the screen, others might require us to attend to all
the red shapes, or to all the triangles, or to something else. Some of
these ways of attending seem to be more basic than others. It seems,
for example, that attending to things in the top part of the screen
might be a primitive task, whereas attending to the triangles could
not be primitive in the same way: we cannot *simply* attend to
the triangles. If we want to attend to the triangles, we need first to
work out *where* the triangles are. If, on the other hand, we
want to attend to the things in the top part of the screen we do not
need to work out whether they are triangles. It is therefore plausible
that when we attend to the triangles we do so *by* attending to
their locations. In this sense attending on the basis of location
seems to be more basic than attending on the basis of shape.



The idea that attending to a location is more basic than attending to
a shape might tempt one to think that attending on the basis of
location is absolutely basic, so that attention is always and only
allocated on the basis of location. If that were right then a theory
of the spatial allocation of attention--a theory about the moving
and focusing of an 'attentional spotlight'--would be
a large and central component in an account of how attention works.
This would be good news for those who want to give a single unified
theory of attention, and it would be good news for the scientific
project of explaining attention more generally, since
attention's spotlight-like behaviours are some of its best
understood aspects (see Logan, 1996).



There are reasons to think that location does play a special role in
the allocation of attention, as the spotlight metaphor suggests. But
the role of location in the allocation of attention is probably not as
straightforward as would be required by the most parsimonious of
spotlight-based theories. Location does have a special role to play
here, but (1) location is not the only property to have such a role,
and (2) the role of location is more complicated than a simple
spotlight metaphor suggests.



Empirical debates about the direction of the spotlight of attention
have focussed mostly on the second of these points. An important
source of data here is case studies contrasting the different patterns
of attention failure that are shown by different unilateral neglect
patients. Such studies suggest that various frames of reference are
involved in the spatial allocation of attention (Behrmann and Tipper,
1999). This indicates that there is no *single* map of
locations determining which items get attention: attention is
sometimes allocated on the basis of location in egocentric space,
sometimes on the basis of location in more complex frames of reference
(a point that was among those raised by Allport, in his influential
critique of the Broadbentian debates (see Allport, 1992, p. 197)).



There are also some well-known experimental effects suggesting that
attention is allocated, not on the basis of straightforward spatial
coordinates, but in ways that are constrained by the distribution of
*objects* in space. The classic work in this area is John
Duncan's demonstration that attention shifts more readily
between two locations that fall within the bounds of a single object
than between equidistant locations that are separated by an object
boundary (Duncan, 1984). Equally important here are findings from
experiments using three-dimensional stimuli, and using virtual
three-dimensional displays. These studies suggest that experimental
participants are unable to differentially attend to depths in an empty
space, but that these participants start to be able to shift their
attention forwards and backward (to a place in front of or behind the
point that their eyes are fixating) when the relevant locations are
ones in which there are objects (see Yantis, 1998).



These converging sources of data indicate that the spotlight of
attention is not allocated simply on the basis of coordinates in any
single spatial frame of reference. That is an important finding for
those attempting to localize mechanisms for the allocation of
attention within the brain (since different brain areas differ in
their mapping of space, and in their representation of spatial
information about the objects within it). It has been influential in
leading psychologists to turn away from simple spotlight metaphors. It
should be noted, however, that these findings do not threaten the core
of the idea that was suggested by the spotlight metaphor: the facts
about what a person is attending to might still supervene on the facts
about *where* that person is attending, even if quite numerous
and sometimes complex factors are responsible for determining which
location that is.



Other effects are somewhat more damaging for a pure spotlight view,
although they also stop short of refuting it entirely. The
more-than-merely-spatial complexity of the way in which attention is
allocated has been nicely demonstrated in a series of experiments by
Dwight Kravitz and Marlene Behrmann (Kravitz and Behrmann, 2011). The
participants in these experiments have their attention cued by a brief
stimulus that is presented at one end of a shape that is shown on a
computer screen. This shape might be a simple rectangle, a rectangle
with bulbous ends, or a more complex 'H' or
'h' shape. It is presented alongside another shape, which
in some cases has the same shape and colour, and in other cases is
different. The resulting allocation of attention is then probed by
measuring the reaction times to stimuli that are presented on and near
these objects. Kravitz and Behrmann find that all the different
properties of their stimuli *interact* to determine the way in
which attention is allocated to the screen on which those stimuli
appear. Most strikingly of all, they find a difference in the
allocation of attention between trials in which the shapes on the
screen are an upper and a lower case 'H', and trials in
which the shapes are an upper case H and number 4, even though this
number 4 shape is exactly the same as the lower case h, but presented
upside down. Such findings suggest that attention, even when triggered
by a simple spatial cue, is not allocated merely on the basis of
location, but also on the basis of shape, colour, and arbitrary
learned meaning.



The discovery that attention can preferentially modulate the
processing of stimuli on account of their colours, shapes, and
meanings does not prevent us from maintaining that the location of a
stimulus has a special role to play in the process by which attention
is allocated to it. More than one line of research in psychology has
sought to identify some one representation in the brain in which items
are encoded in a way that determines the extent to which attention
will be allocated to them. In the longest established of these lines
of research--beginning with the work of Koch and Ullman
(1985)--this representation has been taken to be a *map*,
in some quite literal sense of 'map': the representation
is taken to be one in which every location in some region is
represented, and the representation of these locations is taken to be
in some format that immediately encodes the spatial relations between
them. Every object that is represented is taken to be represented as
being at some location, and the properties assigned to these located
objects are taken to determine the likelihood that attention will be
paid to the location that the objects occupy. According to the theory
that postulates these 'salience maps', location does play
a unique role in determining the way in which attention is allocated,
despite the fact that other properties also contribute to that
allocation.



In more recent treatments of this idea (Pessoa, 2013) such maps are
taken to include representations, not merely of the objective
properties that give an item salience, but also of subjective
properties, such as emotional-valence and
current-motivational-relevance. The more we think of these maps as
being augmented with additional, non-spatial information, the less
spotlight-like the allocation of attention represented in them will
seem to be, but, provided the representation in question is still
understood to be map-like, location can still be understood to have an
important role, and perhaps even a uniquely important one.



Debates about the role of such maps, and about the variety of
subjective and objective properties that are represented within them,
may have some wide-ranging philosophical consequences, concerning more
than just the aptness of the spotlight metaphor. Aaron Henry has
suggested that the viability of some recent philosophical theories
depends on the outcome of these debates. Since the recent
philosophical theories of attention have tended to emphasize the role
of agency in attention, they face potential counterexamples from
instances of involuntary attention. Henry suggests that the threat of
such counterexamples can be defused if the mechanisms of involuntary
attention capture are understood to involve attention being allocated
on the basis of a map in which the agent's own priorities for
action are represented (Henry, 2017).



Although the psychological debates about salience maps are ongoing, an
argument against pure spotlight views can also be made on more
traditional, phenomenological grounds. A pure spotlight theory,
according to which attention is always allocated on the basis of
location, seems unable to account for the sort of case that Hermann
von Helmholtz and William James were concerned with (see section
 1.5).
 There is, as their example suggests, a difference between attending
to the pitch of a note and attending to its timbre, or to its
overtones. This difference in attention does not seem to correspond to
any difference in the location attended. Nor does any purely
location-based theory of attention allocation seem able to account for
the sort attention that one must pay in order to perform a time-based
task, such as finding out which of a group of shapes appears on screen
for longest. Such temporal aspects of attention have been a relatively
late addition to the psychological research agenda (see the papers
collected in Nobre and Coull, 2010). The research concerning them is
beginning to reveal a diverse range of effects, with a range of
similarly diverse neural underpinnings (Nobre and van Ede, 2018). Some
philosophical work has been devoted to the exploration of these
temporal aspects of attention (see Phillips, 2011), but it is work
that has tended to address questions that further our understanding of
the experience and perception of time, without attempting to
contribute directly to our philosophical understanding of attention
itself (see the entry on
 The Experience and Perception of Time).



Since some shifts of attention are not shifts in the location
attended, a theory of the factors that determine which locations a
subject is attending to cannot tell us the whole story about the
allocation of attention. It might nonetheless be a central component
in a theory of some of attention's forms (see Wright and Ward,
2008).


### 2.8 Motor Theories



Work in which electrodes are used *in vivo* to stimulate areas
of the macaque brain known to be associated with eye-movement
coordination has provided strong evidence for the existence of an
anatomical overlap between brain areas involved in eye-movement
control and those involved in determining which stimuli elicit the
strongest responses in visual cortex. There is also evidence that this
anatomical fact has some functional significance. One suggestive
finding is that the links between frontal eye-movement-control areas
and attention-like effects in occipital visual areas are spatially
specific: an electrode that is placed so that it elicits an eye
movement to a particular part of the visual field when activated at
one level will, if activated at a lower level, elicit changes in
neural responsiveness that are exactly similar to the changes that are
seen when attention is shifted to that same location (Moore and
Armstrong, 2003, Armstrong and Moore, 2007).



These facts have been taken to be suggestive of a 'motor
theory' of attention, according to which the processes
underpinning attention are, in at least some cases, truncated versions
of the processes underpinning the coordination of movements of sensory
orientation.



The central idea of such a theory is that "the program for
orienting attention either overtly or covertly is the same, but in the
latter case the eyes are blocked at a certain peripheral stage"
(Rizzolatti *et al*, 1987, 37). Advocates of motor theories
(such as Moore, Armstrong and Fallah, 2003) have characterised their
work as a revival of the picture that Alexander Bain proposed at the
end of the nineteenth century. Bain (as we saw in Section
 1.5,
 above) identified attention with truncated versions of the
motor-control processes that typically bring about attention's
behavioural manifestations -- processes "stopping short of
the actual movement performed by the organ" (Bain, 1888,
371).



These versions of the motor theory should be distinguished from
theories that regard attention and motor control as intimately linked,
but that place no emphasis on the fact that the motor control
processes that have been implicated in attention are processes that
control the movement of *sensory* organs. In these theories
(which are natural but not obligatory concomitants of the
'selection-for-action' views discussed in
 section 2.5)
 attention stands in an intimate relation to motor control more
generally. One line of experimental evidence in support of such a
general connection comes from work by Heiner Deubel and his
collaborators, in which various changes to the way in which an object
figures in action are shown to have an attention-indicating influence
on the perceptual discrimination of stimuli that are presented on or
near that object. In one striking example of this, Deubel and
Schneider found that the way in which attention is allocated to the
space around a 6.5cm wooden X shape depended on whether the subject
was reaching with her left hand to grasp the shape by the top-left and
bottom right arms, or reaching with her right hand to grasp the shape
by the arms at its top-right and bottom left (Deubel & Schneider,
2004). In each case attention was allocated not only to the shape, but
to the to-be-gripped parts of it. (For other evidence of interactions
between attention and action-targeting, see Tipper, Howard, and
Houghton, 1998.)



Motor theories and other action-based theories give a plausible
account of some of attention's instances, but they have
limitations that prevent them from applying with full generality:
Since movement of the eyes, or of the limbs, is always movement *to
a location* motor theories will struggle to account for the
allocation of attention on the basis of anything other than location.
They therefore face the limitations that we saw when considering pure
spotlight theories, of being unable to account for shifts in attention
that do not correspond to differences in the location attended. Nor is
it clear how motor theories should be applied to spatial attention in
those sensory modalities where the orientation of the sense organs is
less straightforward than it is in the visual case. The motor theory
does, nonetheless, provide a plausible and well-supported account of
the location-based variety of visual attention that is displayed in
typical attention-lab experiments.



The success of motor theories in accounting for the sorts of attention
that are found in some typical attention-lab experiments can be given
either an optimistic or a pessimistic interpretation. The optimistic
interpretation sees the motor theory as providing a successful account
of the processing underpinning some of attention's simpler and
more central varieties. The pessimistic interpretation sees the motor
theory as revealing a problem with our usual experimental
paradigms.  The participants in typical laboratory tasks direct
their attention to different parts of their visual field, while
keeping their eyes fixated on a central spot. The behavioural
signatures of attention in such tasks are usually reductions in
reaction time to the attended stimuli. The neural correlates of these
behavioural signatures are certain biases as to which stimuli most
strongly drive the neural circuitry that processes them. The central
finding of the motor-theorists is that these neural and behavioural
effects can result from attenuated versions of the activity
responsible for directing eye movements. The pessimistic
interpretation of this finding is as revealing that signs that have
traditionally been taken to indicate the direction of attention are
actually no more than consequences of the truncated eye-movements that
our experimental paradigms induce, by imposing the restriction that
experimental participants fixate their gaze on a single location. If
that is right then the phenomenon studied in attention labs may not be
the psychologically important one that it has been taken for.



Motor theorists are not the only ones who might be accused of
elevating a theory of some circumscribed subset of attention-related
phenomena into a spuriously general theory of attention in its
entirety. Henry Taylor has shown that, although the ambition to give a
general theory of attention is widespread among the philosophers who
have recently written on this subject, it is seldom found in the
recent psychological literature, where it has proven fruitful to
follow the influential example of Michael Posner by giving somewhat
separate treatments of attention's roles in vigilance, in
perceptual orientation, and in the focalized deployment of processing
resources (Taylor, 2015, 2018; Posner and Boies, 1971). Taylor
suggests that the psychologists' tolerance for pluralism here
should be reflected in our philosophical theories.


## 3. Explanatory Roles for Attention


### 3.1 Attention and Consciousness


#### 3.1.1 Is Attention Necessary for Consciousness?



The question of whether attention is necessary for consciousness has
been answered in various ways. One answer is given by those who think
that lots of unattended items appear in consciousness. A different
answer is given by those who think that only some unattended items
figure in consciousness. A third answer is given if we think that
unattended items figure in consciousness only in special
circumstances. There is some evidence that, independently of any
philosophical commitments, people differ as to which of these views
they find plausible (Schwitzgebel, 2007). There are also some theories
(e.g., Watzl, 2017) in which attention is necessary for
'creature consciousness' in the sense that every conscious
creature must be an attentive one. Such views need not entail that
attention to an object is necessary for the conscious perception of
that object.



At one extreme end of this spectrum is the view according to which
attention to a thing is strictly necessary for consciousness of it, so
that the things to which we are not paying attention do not figure in
our consciousness at all. A number of psychologists endorse this view
(e.g., Cohen *et al*. 2012), as do some philosophers (e.g.,
Prinz, 2012, Carruthers, 2015, Montemayor & Haladjian, 2015). It
has historical precedent in James's remark, at the beginning of
his chapter on attention, that "my experience is what I agree to
attend to"(James, 1890, ch. 11), and in Kames' remark that
"Attention is requisite even to the simple act of seeing"
(Kames, 1769, see Sect
 1.4,
 above).



The evidence that is proffered in support of the view that attention
is strictly necessary for consciousness comes from a range of
experiments showing the surprising extent to which experimental
participants are ignorant of the items to which they have paid no
attention. In Arien Mack and Irvin Rock's 'inattentional
blindness' paradigm, for example, participants who are given an
attention-demanding task pertaining to a stimulus in one part of their
visual field frequently fail to notice shapes or words that are
flashed up elsewhere (Mack & Rock, 1998). In Rensink *et
al*.'s 'change blindness' paradigm the
participants need to see an alternating pair of pictures between ten
and twenty times before they can identify a large but narratively
inconsequential difference between them (Rensink *et al*.,
1997, Rensink, 2002). In the most memorable of these experiments a
large number of participants fail to notice the central appearance of
a man in a gorilla suit when their attention is taken up with the
business of counting the number of passes made by one of two teams in
a concurrent basketball-type game (Simons & Chabdris, 1999).



No single one of these experiments can establish the claim that
attention is always necessary for consciousness. That claim is a
universally quantified one, and is not entailed by any one of its
instances. Nor is it clear that what we see in these experiments
really are instances in which unattended objects drop out of
consciousness altogether. The participants' ignorance of the
gorilla's appearance, for example, is compatible with it being
the case that the presence of the gorilla *does* make a
phenomenal difference to their inattentive experience. To explain
those participants' ignorance we need only say that any
phenomenal difference that the unattended gorilla makes is a
difference that the participants are unable to use in answering the
experimenter's question about whether anything strange happened
in the scene. It may be a phenomenal difference that is epistemically
unusable because it is immediately forgotten (see Wolfe, 1998) or it
may, alternatively, be a difference that is unusable because it is too
unstructured and inchoate to be epistemically mobilizable. In that
case the effect of inattention would be inattentional
*agnosia*, rather than inattentional *blindness* (see
Simons, 2000).



Absolute amnesia for unattended items, or thoroughgoing agnosia for
them, may be indistinguishable from inattentional blindness, both
behaviourally and from the point of view of retrospective
introspection. For that reason it is not a straightforward matter for
the advocates of any of these interpretations of the inattentional
blindness and change blindness effects to rule out the alternative
interpretations. Subpersonal sources of data (such as experiments
using neuroimaging) may be the only sources of data that we have to go
on. (See Rees, *et al*. 1999, for an example in which fMRI data
is used to argue against the amnesia interpretation of inattentional
blindness effects involving written words).



It is only narratively insignificant differences that go unnoticed in
the change-blindness paradigm. Change blindness effects might
therefore be taken as showing, not that there is no consciousness in
the absence of attention, but that there *is* consciousness in
the absence of attention, the contents of which are restricted to the
scene's overall gist. There are difficulties in adjudicating
between these two interpretations experimentally. When features of
gist do seem to be perceived, in the apparent absence of attention,
the defender of the claim that attention is necessary for
consciousness may reply by claiming that attention has been paid to
these items, either in a dispersed, non-focal way (Prettyman, 2013),
or because these features are briefly and involuntarily
attention-catching (Prinz, 2012, p. 119). Without an experimental
operationalization of complete inattention, these rival
interpretations cannot be ruled out, with the result that empirical
debates about the extent of consciousness beyond attention are
currently in something of deadlock, with experimenters being able to
claim only to have demonstrated perception in the 'near
absence' of attention (Li *et al*., 2002, Reddy *et
al*., 2004, Reddy *et al*., 2006), and so providing only
inconclusive support to the hypothesis that attention and
consciousness are dissociable (Koch & Tsuchiya, 2007).



The methodological puzzle that we face when trying to settle the
dispute between different interpretations of the inattentional and
change blindness effects raises the question of whether our
commonsense beliefs about the conscious status of unattended items are
well founded. Such beliefs seem to vary from person to person
(Schwitzgebel, 2007), and to vary with certain features of the context
in which they are probed (De Brigard, 2010). To the extent that we
find it natural to suppose that unattended items do figure in
consciousness, this may simply be owing to a version of the
'refrigerator-light illusion': If our reason for believing
that we are conscious of the things to which we pay no attention is a
reason that depends on our finding that we are conscious of those
things whenever we check on them then that belief is on shaky ground.
A checking procedure cannot provide us with good evidence about the
status of unattended items since the act of checking is itself an act
that involves a shift in attention to the things checked
(O'Regan & Noe, 2001).



Since a direct checking procedure is ruled out we need a more
theory-driven way of assessing the dispute between those who claim
that the consequence of not attending to an item is that the item
drops out of conscious experience and those who claim that inattention
simply puts the subject in a poor epistemic position vis-a-vis
these unattended items. The current state of our theories is such that
it would be premature to try to settle this dispute by an inference to
the best explanation, since neither side of the dispute has a theory
of the attention/consciousness relation that has been worked out to a
degree that would allow the different explanations to be compared. We
can, however, see some of the considerations that the two sides in
this debate might invoke. Those who endorse the idea that attention is
necessary for consciousness can point to the fact that this view
accords well with theories in which attention features prominently in
the explanation of consciousness (e.g., Prinz, 2005, 2012). They may
also be able to develop arguments based on theories of the way in
which consciousness and attention evolved (Montemayor & Haladjian,
2015). Those who prefer the epistemic-deficit interpretation of the
inattentional blindness effects (Mole, 2011, SS7.3.7) can point to
the fact that that interpretation flows naturally from the view
according to which attention to an item provides the sort of
acquaintance that is needed for the use of a demonstrative concept
that refers to that item (a view advocated by Campbell, 2002, and
discussed in section
 3.2
 below): If attention to the gorilla is necessary for the forming of a
demonstrative-involving thought (such as 'That's a
gorilla') then there is an immediate explanation, consistent
with the idea that unattended items nonetheless feature in
consciousness, for the fact that inattentive people are unable to
answer questions such as 'Was there a gorilla?'.



The difficulty in the case of the unnoticed gorilla is to discern
whether unattended items are present to consciousness but present only
as unindividuated items to which no demonstrative reference has yet
been directed, or whether those unattended items are instead absent
from consciousness altogether. Part of this difficulty originates in
the fact that, although most people give no attention to the gorilla,
they *could* attend to him, and would have done so if anything
had prompted them to do so. More data may be available, both to
introspection and to laboratory measurement, in cases where our
failure to attend has some more systemic explanation. Ned Block has
suggested that one such case is found in our perception of peripheral
stimuli, when these are subject to the phenomenon of 'identity
crowding' (Block, 2013a). An individual 'T' or
'F' can be seen reasonably clearly, even when presented in
a peripheral part of the visual field. But if additional characters
are presented alongside this individual character, then the properties
of those characters become prone to perceptual confusion. Attention
seems to bind together properties from all of the characters in the
vicinity of the one individual that we are trying to pick out. It
therefore seems that, in the perceptual periphery, attention cannot be
directed onto a region that fits an individual character tightly. Due
to this 'crowding' effect, individual letters or shapes
become impossible to individuate from the others with which they are
clustered, when they fall into parts of the visual field that are
outside of the high-definition centre. The properties of objects that
are crowded in this way can nonetheless be seen, and the fact that
several items are present can be reliably reported. On the basis of
empirical and introspective considerations, Block claims that, even in
cases where the crowded characters share all of their features with
the others by which they are crowded, these crowded characters are
consciously discriminated from their surroundings. He claims that
these characters figure as objects in consciousness. Since attention
cannot be allocated to anything more fine-grained than the crowd of
which these characters are a part, the characters are not themselves
objects to which attention is paid. Block therefore takes
'identity crowding' to give counterexamples to the claim
that we are conscious of objects only when paying attention to
them.



Block's claim that the crowded characters figure in
consciousness as individuated objects, rather than as parts of some
feature-rich texture, has been contested (Taylor, 2013, Richards,
2013). In response, Block has suggested that an inference the best
explanation of several related phenomena favours his interpretation of
the effect (Block, 2013b).



Inference to the best explanation is always a hazardous business,
especially in the vicinity of an explanatory gap. In the
interpretation of identity crowding, as in the interpretation of
inattentional blindness, the inescapability of abductive
considerations suggests that our answer to the question of whether
attention is necessary for consciousness may have to wait until we
have a better understanding of the relation of attention to
demonstrative reference (of the sort that is involved in thinking
'That's a gorilla'), and perhaps until we have a
better understanding of attention's role in epistemology more
generally. (See
 sections 3.3 & 3.4 ,
 below.)


#### 3.1.2 Is Attention Sufficient for Consciousness?



In addition to disputes about whether we are conscious of
*only* those things to which we attend, there are also disputes
about whether we are conscious of *everything* to which we
attend. If we were then a complete theory of attention might be given
by giving an account of the way in which attention modulates
consciousness.



Declan Smithies has argued in favour of a position according to which
everything that is attended to is consciously attended to. He claims
that all instances of attention must be consciousness-involving, on
the grounds that (1) all such instances must have a connection with
their subject's 'rational-access' to the contents of
her experience, and (2) there is no connection to rationality in the
case of processing that is wholly unconscious. Smithies' view
is, therefore, that attention is essentially involved in the
'rational-access' of consciously experienced contents
(Smithies, 2011). The nature of any such connection between attention
to an experience and the justificatory force of that experience is
itself a source of ongoing controversy: Johannes Roesller has argued
that John McDowell's theory of perceptual experience's
reason-giving force cannot account for the role played by attention in
experience (Roessler, 2011); Susanna Siegel and Nicholas Silins have
claimed that the doxastic influence of an experience can be an
instance of rational access even when that experience receives no
attention (Siegel & Silins, 2014); Terry Horgan and Matjaz
Potrc have argued that the justification of beliefs by experience
must outrun both the contents of attention and the contents of
consciousness (Horgan and Potrc 2011). Here, as above,
one's understanding of attention and one's understanding
of epistemology constrain one another, and may provide a theory-driven
route by which to settle questions about the possibility of
unconscious attentiveness.



The claim that all attention is conscious attention sits uneasily with
certain empirical results indicating that consciousness is not
required for the operation of those psychological processes that are
responsible for certain effects that are usually taken to be
signatures of attention. In an experiment by Yi Jiang *et al*.,
(2006), for example, participants are presented with
attention-attracting stimuli in such a way that, thanks to an
arrangement of mirrors, these stimuli are given to just one eye.
Because a more vivid stimulus is presented to the other eye, and
because this more vivid stimulus wins the competition for
consciousness that occurs in such cases of binocular rivalry, these
experimental participants do not consciously experience the less vivid
stimulus. Those unconsciously processed stimuli include erotic
photographs. And those photographs do seem to elicit shifts of
attention, despite being unseen, as is evidenced by the fact that
consciously experienced stimuli that are presented in the same
location as these unseen attention-grabbers are more accurately
responded to in an attention demanding task (involving detecting the
orientation of gabor-patches). One striking finding from Jiang *et
al*.'s experiments is that the way in which these unseen
photographs attract and repel attention depends on the sexual
orientation of the experimental participants.



A natural interpretation of these experiments is as showing that the
erotic pictures capture the participants' attention, despite the
fact that those participants have no conscious experience of them.
This suggests--although it does not conclusively
demonstrate--that one may be attending to a thing without being
conscious of it. The same conclusion is suggested by a quite different
set of experiments involving a patient with blindsight.  These
experiments show that, even though the blindsighted patient has no
experience of cues presented in his scotoma, those cues can elicit the
facilitation of processing and reduction of reaction times that are
usually taken to be the signatures of attention (Kentridge &
Heywood, 2001, Kentridge *et al*., 2004).



One complaint against both these lines of evidence is that they do not
enable us to distinguish between attention to a thing and attention
that is directed to a part of space (in which that thing happens to
be), with the result that they cannot demonstrate attention *to a
thing* in the absence of consciousness of that same thing (Mole,
2008a). Research by Liam Norman, Charles Heywood and Robert Kentridge
goes some way towards addressing this complaint. Norman, Heywood and
Kentridge present normal participants with a screen showing an array
of small, rapidly flickering Gabor patches. Objects the boundaries of
which are defined by changes in the orientations of these patches are
not consciously experienced: Participants merely see the whole screen
as a flickering array of patches. Cues that direct the attention of
those participants do nonetheless seem to draw attention to these
unseen objects, as indicated by differences in the response times to
items that are subsequently presented in and outside of their
boundaries (Norman, Heywood & Kentridge, 2013).



Such experiments show that there is an influence operating between
unconscious processing and the direction of attention, and perhaps
indicate that attention can be paid to objects that make no showing in
conscious experience (Mole, 2014a). They therefore place a limit on
the closeness of the relationship that can be claimed to exist between
attention and consciousness.



The disputes about whether attention is sufficient for consciousness,
necessary for consciousness, or both, are related to questions about
attention's metaphysics. The claim that attention is not
sufficient for consciousness is typically made as part of a defence of
the idea that attention and consciousness are underpinned by two
distinct brain processes, which can occur independently (see, e.g.,
Koch and Tsuchiya, 2007). The claim that the things to which we attend
are a proper subset of the things that appear in our consciousness is
required by those who, like Locke (see Section
 1.3),
 think that there is a process of conscious thinking, and that this
constitutes attention when it happens in a certain way.  
And the claim that attention is both necessary and sufficient for
consciousness is required by those who think that the process by which
things come to consciousness is identical to the process by which
attention is allocated (Prinz, 2005, 2011). Some scientific theories
of consciousness also carry strong commitments concerning its
relationship to attention: Taylor Webb and Michael Graziano emphasize
these commitments in making the empirical case for their
'Attention-Schema' theory, according to which
consciousness emerges from processes in which the control of attention
requires a schematic representation of the way in which attention is
being allocated (Graziano and Webb, 2014; Webb and Graziano,
2015).


#### 3.1.3 How Does Attention Modulate Phenomenology?



Whether or not one thinks that attention is always responsible for
bringing things into our consciousness, there are good reasons to
think that changes in the direction of our attention can make some
difference to the character of conscious experience. Phenomenologists
and Gestalt psychologists have characterized this difference in
various ways, with Maurice Merleau-Ponty emphasizing the way in which
attention can configure the figure/ground structure of perceived space
(Merleau-Ponty, 1962, Chp.3-4), and Aron Gurwitsch (Gurwitsch,
1964) elaborating a theory in which the configuration given by
attention has a more complex, three-part structure (explained in
Arvidson, 2006). In the second half of his 2017 book, Sebastian Watzl
develops a similar suggestion, on the basis of his claim that the role
of attention is to impose a priority structure on our mental lives
(see above
 SS2.4),
 (Watzl, 2011, 2017).



There is currently some dispute about whether the differences made by
shifts of attention can be adequately characterized as differences in
the *content* of the attended experience. If, as Watzl
contends, they cannot, then phenomena of attention create a serious
difficulty for any fully general attempts to explain the character of
conscious experience by reference to the contents represented in it
(Chalmers, 2004).  Such explanations might still be viable in
circumscribed domains (Speaks, 2010).



A series of studies by Marisa Carrasco and her collaborators have
examined the influence of attention on the character of conscious
experience. These have revealed that the phenomenal differences
produced by shifts of attention include differences of perceived
brightness, contrast, and saturation of colours, but do not include
differences of hue (Carrasco, Ling & Read, 2004, Fuller &
Carrasco, 2006). Ned Block has suggested that these perceived
differences should not be thought of as differences in the
*content* of experience, since to characterize them in that way
would be to take it that attending to an item creates an illusion as
to its brightness, contrast, etc.; a result which he takes to be
implausible. Block therefore interprets Carrasco's findings as
indicating an aspect of experience that cannot be accounted for with a
theory in which the phenomenal character of an experience is a
function of that experience's content (Block 2010).



There have been similar disputes, transacted on the basis of more
introspective considerations, concerning the effects of attention on
the perception of ambiguous figures (such as the Necker Cube). In
response to some considerations that were first raised by Fiona
Macpherson (Macpherson, 2006), Bence Nanay has suggested that the
effects of attention on the perception of such figures can be
explained by those who maintain that every difference in consciousness
is a difference of content (Nanay, 2010, 2011). His contention is that
the effects of attention on the character of conscious experience
should be understood as including a modulation of the specificity of
an experience's content, in which the representations of
determinable properties are made more or less determinate. The issues
here are similar to those concerning the way in which blurriness
should be thought to enter into visual experience (see Section 4.4 of
the entry on
 representational theories of consciousness).



Mattia Riccardi casts attention in a rather different phenomenological
role, suggesting (in opposition to the proposal of Matthen, 2010) that
attention explains the *presentness* that differentiates
one's perceptual experiences of real objects in one's
immediate environment from one's experiences of objects that are seen
in photographs, or that are pictured by the mind's eye during
episodes of vivid imagination (Riccardi, 2019).


### 3.2 Attention and Demonstrative Reference



Consciousness is only one of the philosophically puzzling mental
phenomena that have been thought to be related to attention in ways
that may prove to be explanatorily revealing. *Demonstrative
reference* is another. One advocate of the idea that attention
contributes to the explanation of demonstrative reference is John
Campbell, who writes that:



> 
> ... the notion of conscious attention to an object has an
> explanatory role to play: it has to explain how it is that we have
> knowledge of the reference of a demonstrative. (2002, 45)
> 



A similar idea was explored in the manuscript on Theory of Knowledge
that Bertrand Russell abandoned (under the influence of Wittgenstein)
in the summer in 1913. In that work Russell gives the following
statement of the idea that reference to particulars requires attention
to them:



> 
> At any moment of my conscious life, there is one object (or at most
> some very small number of objects) to which I am attending. All
> knowledge of particulars radiates out from this object. (1913, 40)
> 



In support of the Russellian claim that there is an explanatory
relation between attention and demonstrative reference, Campbell
develops two lines of thought.



His first line of thought comes from reflection on examples concerning
the requirements that have to be met in order to understand
demonstrative expressions in conversational contexts where one of the
participants in the conversation uses expressions such as 'that
woman', but where various women are present, all of whom are
possible referents for this demonstrative. Knowing which women is
meant, according to Campbell, requires attending to the woman in
question and knowing that it is to her that the speaker was attending.
This is intended to show more than just that the direction of the
speaker's attention is a possible source of evidence for what
that speaker means. It is intended as showing that attention and
reference stand in a particularly intimate relationship--a
relationship that Campbell characterizes by saying that
'knowledge of the reference of a demonstrative is provided by
conscious attention to the object' (p. 22).



The second line of thought that Campbell develops in support of the
view that attention explains demonstrative reference is one pertaining
to deductive arguments in which the premises refer to items that are
picked out by demonstratives: Arguments such as '(1) That is F.
(2) That is G. Therefore (3) That is F and G'. Campbell's
thought here is that such arguments depend for their validity on there
being no possibility of equivocating on the meaning of
'that', as it occurs in the two separate premises. Such
arguments can only figure in rationally-entitling reasoning so long as
there is a single fixing of the referent of 'that' in both
premises. This reference fixing, Campbell thinks, is achieved if and
only if there is no redirection of attention between the premises.
Again this is intended to show more than just that there is some
causal or evidential relation between attending and referring. It is
intended to show that the role played by attention in fixing the
reference of a demonstrative is analogous to the role played by a
Fregean Sense in fixing the reference of a proper name (Campbell,
2002, Chapter 5).



The explanatory approach that Campbell advocates, and that Russell
considered, has traditionally been thought to suffer from a problem of
circularity. This problem was urged by Peter Geach in *Mental
Acts* (1957). Geach considers the suggestion that we can use
attention to explain our ability to make reference to the things that
we perceive, but thinks that no such suggestion can provide a genuine
explanation of reference because:



> 
> ... it is quite useless to say the relevant sense-perceptions
> must be attended to, either this does not give a sufficient condition,
> or else "attended to" is a mere word for the very relation
> of judgment to sense perception that requires analysis. (1957, 64)
> 



Geach's threat of circularity can be avoided if an independently
given theory of how attention is constituted can be shown to
illuminate the way in which reference is fixed by it. Imogen Dickie
has attempted to show just this. In a 2011 paper Dickie shows that
cognitive psychology provides us with a theory of the role played by
attention in tracking objects over time. She suggests that such a
theory can be used to account for the way in which attending to an
object removes any knowledge-defeating component of luck from our
inferences involving it, thereby establishing the attended object as a
possible topic of demonstrative thoughts (Dickie, 2011, 2015). This
treatment of attention exemplifies some of the central themes in
Dickie's more general attempt to explain how thoughts come to be
about ordinary objects (and so how singular terms come to refer to
those objects). The explanation that she offers is one in which a
thought comes to be about a thing when the justificatory practices in
which that thought figures are anchored to the object in question (in
a sense of 'anchoring' that Dickie spells out in detail
(Dickie, 2015)).



Whether or not a theory of attention can be turned into a non-circular
explanation of demonstrative reference, the idea that attention and
reference are related does seem to cast light on what goes on when we
understand referring expressions. Campbell's examples succeed in
suggesting that what we attend to and what we refer to are often the
same. There is also some empirical evidence, coming from developmental
psychology, indicating that attention-related abilities play a crucial
role in the infant's development of an understanding of its
caregiver's demonstrative use (see
 Section 3.3).
 Lessons have been drawn from this that are not only about the
comprehension of linguistic expressions. This developmental work has
also been taken to imply something about our grasp on directly
referring *thoughts*. The idea here - as in the work of
Dickie and Campbell - is not only that attention contributes to
our production and comprehension of linguistic expressions that have
particular referents, but that it also contributes to the
establishment of those referents as the contents of our thoughts. In
addition to these developmental considerations, Michael Barkasi has
suggested that the nature of attention's contribution to fixing
the reference of thoughts can be illuminated by considering the
pattern of neural projections to the frontal eye fields. Whereas
Campbell characterizes attention in *epistemic* terms, Barkasi
favours a sub-doxastic characterization, in which attention
'sets targets' and thereby regulates the flow of visual
information (Barkasi, 2019).


### 3.3 Attention and Other Minds



There are empirical results, coming from developmental psychology,
which are suggestive of an intimate link between the development of
various abilities related to attention and the development of various
capacities that are involved in understanding the mental states that
are expressed in interactions between the infant and its
caregiver.



An ability to appreciate what others are attending to appears to be a
crucial stage in a normal infant's development towards
understanding the fact that its caregivers' utterances have
referential intentions behind them. More generally, capacities for
attention develop at important milestones on the route to the
acquisition of some distinctively human cognitive capacities (Moore
and Dunham, 1995). There is a distinctive developmental pathway in
which normal human infants develop an ability and a willingness to
attend to their mother, an ability and willingness to attend to the
thing that she is attending to, and then, most importantly, an ability
and willingness to enter into episodes in which there is a third
object that mother and child are attending to *jointly*, with
mutual understanding of the fact that their attention is shared
(Reddy, 2010, Trevarthen, 2011). In these episodes infants and
caregivers employ complex cues, involving speech, gaze-following, and
pointing.



There is good evidence that the child's progression along this
pathway is related to its development of abilities to respond
appropriately to the mental states of others, and to the development
of its ability to acquire new vocabulary on the basis of an
understanding of what the words used by its mother refer to. A
longitudinal study suggests that the earlier stages in this pathway
are predictive of the age at which infants reach the later ones
- thereby providing some evidence for the hypothesis that this
sequence is a causal one - with the mastery at twelve months of
pointing as a means to direct the attention of others being predictive
of false belief understanding at the age of fifty months, even when
factors relating to temperament and language are factored out (Sodian
& Kristen-Antonow, 2015). Another source of evidence comes from
the fact that the arrested development of these attention-involving
abilities is a revealing marker of the impairments suffered by
autistic children (Kanner, 1943, Hobson and Hobson, 2011). 
Further evidence may also come from the fact that a lack of such
abilities is related to limitations in the mental-state attribution
abilities of non-human primates, although this last claim is more
controversial (Call & Tomasello, 2005).



Some progress has been made towards extracting philosophical lessons
from the empirical work indicating that joint attention has a role to
play here, in the explanation of distinctively human aspects of
cognitive and social development, and also - once that
development is complete - in the explanation of the way in which
some elementary social phenomena are transacted. (For several
developmental examples, see the papers collected in Eilan, *et
al*. 2005, and Seemann 2011; for a discussion of joint attention
in adult cases of shared intention, see Fiebich and Gallagher, 2012,
who argue that jointly attending has a basic, elementary status, as
the most minimal instance of a joint action.)



One of the points at which philosophical difficulties arise is in
characterizing the *sharedness* of the attention that is
implicated in this developmental trajectory. Christopher Peacocke has
argued that the way in which joint attention episodes are shared
involves a kind of reciprocal recognition of the other's
recognition of one's own attention, and that it therefore
involves a kind of mutual openness that is analogous to the openness
of 'common knowledge', as that notion figures in
philosophical analyses of communication and convention (see the entry
on
 convention).
 Since joint attention is achieved by young children, its achievement
cannot plausibly be thought to make any sophisticated intellectual
demands. Peacocke therefore argues that awareness of reciprocated
openness must be more fundamental than the intellectual achievement of
common knowledge.  He suggests that it should instead be
understood as a variety of *perceptual* awareness that makes
such common knowledge possible (Peacocke, 2005). John Campbell shares
Peacocke's view of joint attention as being a perceptual
phenomenon, as opposed to a phenomenon that is achieved when
one's perception is reflected on in a certain way, but Campbell
differs from Peacocke in taking the person with whom attention is
shared to be fellow *subject* of the joint experience, not an
object who figures in the *content* of the experience that each
joint-attender individually has (Campbell, 2002, Ch. 8).
Campbell's attempt to shift the explanation of sharedness from
the cognitive to the perceptual domain is rejected by Lucas Battich
and Bart Geurts (Battich and Guerts, 2020), who suggest that
Campbell's view suffers from problems that originate in his
relational conception of perception. They therefore claim that the
issues here cast light on the long-running debates between
representation-based and relation-based theories of perception (see
the entry on
 the problem of perception).


### 3.4 Attention and Knowledge



The apparent links between attention and demonstrative reference (see
section
 3.2)
 and attention and knowledge of other minds (see section
 3.3)
 might be special instances of a more general connection between
attention and the making of epistemic moves. A general connection of
that sort may have been what Descartes had in mind when he suggested
that attention to clear and distinct ideas is a necessary condition
for those ideas to realize their special epistemic potential (see
Section
 1.1).
 It might also be what Stewart had in mind when he suggested that
"Some attention [is] necessary for any act of memory
whatever" (see Section
 1.4).
 Kant's anthropological writings also cast attention in a
crucial epistemic role, as explaining the control that one can exert
over representations in thought and in imagination, where this perhaps
includes the kind of imagination that Kant takes to be involved in
making one's experiences into experiences of an objective
spatiotemporal world (Merritt & Valaris, 2017).



Although each of these philosophers have tended to frame it in a way
that reflects their other theoretical commitments, some version of the
idea that attention is always involved in the making of epistemic
moves can be made pre-theoretically plausible. The inattentional
blindness experiments, in which participants are visually presented
with large changes while attending to something else, show that
inattentive people can fail to notice all sorts of perceivable things
that attentive people would find obvious. Something exactly similar
seems to be true in the case of a priori reasoning: just as no item is
so large, so central, and so well-lit that no conscious and sighted
observer could miss it, so there is no step in reasoning that is so
simple, so compelling, and so obvious, that every thinker, whether
attentive or inattentive, can be expected to recognise it. Just as the
inattentional blindness effects might seem to show that there are
attentional demands that a thinker has to meet before his perceptual
encounter with things can provide him with knowledge of them, so it is
plausible that there are similar attentional demands that have to be
met before the thinker's grasp of a thought gives her a
justified belief in that thought's consequences. This
interpretation of the inattentional blindness effects is, however,
controversial. Nicholas Silins and Susanna Siegel have suggested that
- even if inattention does sometimes explain a perceiving
person's failure to form a belief about the things happening in
their visual field - unattended aspects of experience are
nonetheless capable of providing justification for such beliefs
(Silins and Sigel, 2019). Emile Thalbard argues to the contrary
(Thalabard, 2020).



In both the a priori case and the perceptual case, the acquisition of
knowledge seems to require attention on at least some occasions, and
in both of these cases that requirement seems to be a
*practical* one. It may be that knowledge of some propositions
is required if one's experience with a gorilla is to provide one
with knowledge of the gorilla's presence (with the propositions
here being of a sort that could serve as a major premise in an
inference by which one's perceptual experience was interpreted),
but the requirement on gaining knowledge from experience cannot be
that one must be bearing such propositions in mind. The same is true
in the a priori domain. What is required before an a priori
entitlement can be recognized cannot be that one has to entertain some
prior knowledge of a proposition from which that entitlement can be
deduced. To suppose that occurrent propositional knowledge is what is
necessary for such moves would be to embark on the regress set by
Lewis Carroll's tortoise to Achilles (Carroll, 1895). What
epistemic move-making requires is not occurrent knowledge of a
proposition. The thing that it requires is the right sort of active
attention.



The attentional requirements that have to be met before one can
acquire knowledge from experience or recognize an a priori entitlement
are not requirements merely for alertness. They are not captured
merely by saying that, in order to gain knowledge, the thinker has to
pay some attention to the relevant ideas. A thinker may be attending
to a syllogism, but, if he is attending to its rhythm, he may still be
unable to see that the conclusion follows. A non-question begging
characterisation of the attentional requirements of knowledge
acquisition in general would be an important contribution to
epistemology. Current work on attention, focussing as it does on
attention as a perceptual phenomenon, may give us only part of the
general theory that we need. Work on the purely intellectual forms of
attention continues to be scarce. This shortcoming has been emphasized
by Mark Fortney, who argues that the neglect of intellectual attention
has led philosophers to misinterpret some of the claims made in the
empirical literature on attention and consciousness (Fortney, 2019).
Fortney also claims that considerations pertaining to intellectual
attention should have a central role in debates about the transparency
of phenomenology, and about the consequences of this transparency for
the epistemology of self-attributed thoughts (debates that are
exemplified, in Fortney's discussion, by Byrne, 2018). Fortney
suggests that, when attention is given this role, certain results from
cognitive psychology cast light on these debates. He thinks, when seen
in this light, some of the claims that have been made about the
transparency of occurrent thought start to seem dubious (Fortney,
2020).


### 3.5 Attention and Voluntary Action



Attention's involvement in voluntary *action* is a lot
harder to study in a controlled experiment than its involvement in
perception. The theories of attention emerging from experimental
psychology have, as a result, focused almost exclusively on
attention's perceptual instances. In this respect they contrast
with theories that were developed in the period before psychology and
philosophy split, in which the action-involving aspects of attention
were much more prominent. William James, for example, suggests in the
*Principles of Psychology* that 'volition is nothing but
attention' (James, 1890 p. 424), and at one time (in what might
be read as an anticipation of the competition-based theories discussed
above, in
 SS2.6)
 he proposed that "Attention, belief, affirmation, and motor
volition, are [...] four names for an identical process,
incidental to the conflict of ideas alone, the survival of one in
spite of the opposition of the others." (1880).



The issues surrounding attention's relationship to the
voluntariness of action are parallel to some of the issues surrounding
attention's relationship to the consciousness of perception. It
seems natural to think that attention is necessary for the voluntary
performance of finely tuned behaviours, much as it seems necessary for
the conscious perception of fine detail. But it does not seem natural
to think that we must be paying attention to the execution of every
act that we voluntarily perform, any more than it seem natural to
suppose that we must pay attention in order to be consciously
perceiving anything at all. A case could therefore be made, on
commonsense grounds, for claiming that attention figures in the
production of some but not all voluntary behaviours. One can imagine
this view being challenged by a theorist who claimed that attention is
necessary for any action to be voluntary, arguing that there is an
illusion (analogous to the refrigerator light illusion) that gives us
the mistaken impression that our inattentive acts are voluntary too.
As in the case of attention and consciousness, there is a
methodological puzzle (with epistemologically deep roots) about the
sort of evidence that could settle this issue. This may be a topic for
future research. While resisting the idea that attention is either
necessary or sufficient for an act to be voluntary, Denis Buehler has
argued that there is a central role for attention in the explanation
of flexible goal-directed behaviour (Buehler, 2019). In cases where
that behaviour involves the exercise of a skill, Alex Dayer and
Carolyn Jennings have argued against the idea that any simple account
of attention's role in it can be given, claiming that a theory
of attention's role in skilled performance must instead be
'pluralist' (Dayer & Jennings, 2021).



The separation of attention's role in action from
attention's role in perception is somewhat artificial,
especially when the perception in question is perception of
one's own moving body. Psychological research into that
particular form of perception has been largely independent of research
into the role of attention in vision and audition. A 2016 paper by
Gregor Hochstetter reviews the research into this bodily case, and
argues, following Marcel Kinsbourne (1995, 2002) that internal
representation of a 'body image' must play some role in
guiding attention during normal bodily awareness (Hochstetter,
2016).


## 4 Attention and Value



Attention's contribution to our understanding of values has been
relatively underexplored in the recent literature. The range of
value-theoretic contexts in which attention makes an explanatorily
significant appearance is nonetheless broad.


### 4.1 Attention in Aesthetics



The subject matter of aesthetics can be demarcated in various ways,
each of which is somewhat controversial (see Lopes, 2014). A natural
thought here is that aesthetics might be identified as the branch of
philosophy that is concerned with one particular sort of experience.
If this proposal is to be informative then it obviously needs to be
supplemented with some specification of which sort of experience that
is. It is clear that this specification cannot be given via an
extensional specification of the objects that are experienced: the
same wine might be experienced by the connoisseur and the thirsty man,
with only one of their experiences being aesthetic; the same painting
might be seen aesthetically by the art lover, and from a purely
financial point of view by its dealer.



One response to this would be individuate experiences more finely than
their objects, by instead identifying some particular set of
*properties* that are experienced as belonging to those objects
in the aesthetic case (see the section on aesthetic objects in the
entry on
 the concept of the aesthetic).
 An alternative response would be to consider not only the contents
that are experienced, but also the way in which the subject
experiences them, perhaps by identifying some particular
*attitude* that characterises the subject in the aesthetic
case, or perhaps by identifying some mode of attention that that
subject instantiates (see the section on the aesthetic attitude in the
entry on
 the concept of the aesthetic).



Attempts to identify such an aesthetic mode of attention are
well-represented in the philosophical tradition. Kant's famous
claims about judgements of beauty having a first moment of
disinterested pleasure are usually read as a paradigm of the
attitude-identifying approach (see the entry on
 Kant's aesthetics and teleology),
 but Jessica Williams has argued that Kant must also be operating with
a notion of aesthetic attention, as being a mode of attention
involving a distinctive combination of imagination and understanding
(Williams, 2021).



Some such notion of attention also plays a central role in R.G.
Collingwood's account of the way in which art (and, in
particular, literature) contributes positively to a society's
culture. Collingwood describes attention as "the assertion of
ourselves as the owners of our feelings", and takes this
self-assertion to be crucial in enabling us to exercise volition over
those feelings, so that "Their brute power over us is thus
replaced by our power over them" (Collingwood, 1938, p. 222).
Collingwood therefore takes the diminution of a society's
artistic culture to make it vulnerable to emotive influences (while
himself suggesting that this might best read, not as a broad
philosophical claim, but as a point about Europe in the nineteen
thirties).



Attempts to demarcate the aesthetic via the identification of an
aesthetic attitude, or of an aesthetic mode of attention, have been
attacked -- for their details, and for their more general
orientation (most famously by George Dickie, in his 1964 paper). Those
lines of attack have led to a widespread acceptance of the idea that
there is something wrongheaded about specifying necessary and
sufficient conditions for qualifying as aesthetic via the
identification of some particular aesthetic attitude. Many
philosophers nonetheless retain the idea that there are informative
things that can be said, in the service of less strictly defined
theoretical ends, about the sorts of attitudes that are often found to
be exemplified in aesthetic cases. It is in this spirit that some
ideas about distinctive forms of aesthetic attention have recently
been revived.



Servaas van der Berg suggests that a distinctive mode of attention can
be seen in cases of aesthetic appreciation (van der Berg, 2019). He
claims that this mode of attention is distinguished by its
motivational structure, which has a form that is similar to the
motivational structure of game playing, as theorised by Bernard Suits
(Suits, 1978) and Thi Nguyen (Nguyen, 2020). This structure is one
that inverts the normal order of priorities between means and ends: in
normal actions one's means are typically taken in order to bring
about one's ends, but the game-playing golfer (for example)
instead adopts the end of getting his ball into a hole in order that
he can take the means to reaching that end. Van der Berg argues that a
similar inversion is seen in aesthetic appreciation, where the
cognitive means that are required in order to reach understanding
provide the reasons for adopting the end of understanding an item that
is being appreciated aesthetically.



Bence Nanay has set out a position with similar aims -- not
aspiring to give necessary or sufficient conditions for the aesthetic,
but aiming to cast some light on the way in which certain central
cases of aesthetic experience operate. He does this by giving a theory
of the distinctive way in which our attention is engaged in the course
of these experiences. Nanay emphasizes the psychological distinction
between focused and distributed attention, and uses examples from a
range of arts to suggest that aesthetic experiences often require
attention of both sorts.  He also suggests this contributes to
the value that we place on such experiences (Nanay, 2015, 2016).


### 4.2 Attention in Ethics



Simone Weil suggests that attention has an absolutely central role in
ethics, and in value theory more broadly, writing that:



> 
> The authentic and pure values - truth, beauty and goodness
> - in the activity of a human being are the result of one and the
> same act, a certain application of the full attention to the object.
> (Weil, 1986, p. 214)
> 



This apotheosizing of attention provides the basis for Weil's
claims about priorities for education. On these points, her position
is shared by a number of other figures whose work sits at the
interface of philosophy and literature (see Mole, 2017). Christopher
Thomas has suggested that the role played by attention in Weil's
'ethics of affliction' can be interpreted as an attempt to
put some central notions from Kant's aesthetic theory to ethical
work (Thomas, 2020).



The influence of Kant was in the foreground, together with the
interactions between ethics and aesthetics, when Weil's claims
about attention's import were developed in the work of Iris
Murdoch. Murdoch suggests that there are certain forms of attention
that play an essential role in the exercise of the virtues (Murdoch,
1970, see Bagnoli, 2003, Mole, 2006). She implies that a capacity for
these forms of attention can be cultivated through experiences of
beauty. These themes have been taken up by Dorothea Debus, who places
particular emphasis on Weil's claim that it is *full*
attention to which cardinal value is attributed (Debus, 2015). Antony
Fredriksson and Silvia Panizza suggest that the aspects of attention
that Murdoch takes to be important are seen with particular clarity if
one adopts the perspective of Maurice Merleau-Ponty's account of
attention, in which the *openness* of the attentive mind is
emphasized (Fredriksson & Panizza, 2020). Nicolas Bommarito has
developed an account of modesty along broadly Murdochian lines, as
being a 'virtue of attention'. He argues that this avoids
epistemic difficulties that other accounts of modesty face, if they
instead characterize modesty as requiring false beliefs about the
extent of one's strengths (Bommarito, 2013).



Similar issues are approached from a somewhat different direction by
Peter Goldie (Goldie, 2004), and Michael Brady (Brady, 2010), both of
who relate attention and virtue to the epistemic significance of a
person's emotional life. Both Goldie and Brady suggest that the
attention-modulating profile of an emotion is essential to it, and
both claim that this modulation of attention by emotion plays an
ineliminable role in our having a full appreciation of the evaluative
properties that we encounter in the world around us. Goldie and Brady
disagree as to how this epistemic role should be characterized, with
Goldie taking the experience of one's own emotion to itself be a
reason-giving experience, with an epistemic authority analogous to
one's experiences of the things in one's visual field,
whereas Brady takes the emotional subject's experience of items
in the world to have an epistemic authority that is not shared by the
subject's experience of their own emotional state, so that that
state's epistemic significance must instead be exhausted by its
influence on our outwardly-directed attention (Brady, 2013).


### 4.3 Attention in Social and Political Theory



Many theorists and commentators have noted that some of the largest
businesses are, like Google and Facebook, ones that receive very
little money from the end-users of their best known products, but that
do receive an enormous amount of attention from those users. Writers
who have noted this have often taken it to be symptomatic of a
condition that contributes centrally to the current *zeitgeist*
(Williams, 2018, Odell, 2019). This contribution is typically taken to
be a deleterious one. Michael Goldhaber seems to have been among the
first to describe this condition as a shift from an 'information
economy' to an 'attention economy' (Goldhaber,
1997), following Herbert Simon's suggestion one might give an
economic construal of the fact that attention becomes scarce when
information is abundant (Simon, 1971).



The suggestion that the present century has seen a distinctive
commodification of attention has become widespread. This shift has
been theorized using the conceptual resources of various social and
political philosophies. Jonathan Beller exemplifies a broadly Marxist
approach, by offering an 'attention theory of value'
(Beller 2006). Clinton Castro and Adam Pham draw on Debra Satz's
notion of 'noxious markets' to argue that technologies
designed to maximize attentive engagement should be regulated in ways
analogous to the regulation of the tobacco industry (Castro &
Pham, 2020, drawing on Satz, 2010). Georg Franck uses concepts drawn
from the work of Levinas and Heidegger to give an account of the
attention economy's role in mediating our transactions of mutual
recognition and respect (Franck, 1998).



The technologies that have driven this social change do indeed have
effects on attention. Empirical studies that have measured these
effects have tended to frame them with reference to their downstream
social consequences, rather than their immediate cognitive basis.
Rosen, Carrier and Cheever, for example, observe the effects of social
media use on the study habits of students at school and university,
and relate these effects to educational performance, in order to
suggest some pedagogical strategies by which these effects might be
ameliorated (Rosen et al, 2013). Such theorists have made relatively
little theoretical contact with the accounts of attention offered by
philosophers or cognitive psychologists, although there are some (such
as Atchley and Lane, 2014) who refer to a bottleneck theory of
attention, in order to explain the way in which attention-demanding
technologies reduce the attention that is available for other purposes
(see
 SS2.1,
 above). Rather than referring to theories of the cognitive basis of
attention, claims about the psychological effects of the attention
economy have often been framed with reference to theories of the
psychological basis of addiction (e.g., Bharvaga and Velsquez,
2020).