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The Moon Illusion,
by Donald E. Simanek |
The sky-dome model of the moon illusion, from the 1872 "Buch der Erfindungen" (book of inventions) vol. 2, p.239. This is an example of a misleading and nearly incomprehensible illustration that explains nothing. Exercise: list all the mistakes in the picture. |
If there's a mental map or model, it need not be assumed to be located in a particular place in the brain. Very likely it is an interactive linking of specific visual functions distributed over various locations in the physical brain.The mental sky-dome model.
This commonly seen explanation postulates that we have in our minds a mental map or model of the shape of the sky. We use this model as a real-time reference surface for objects too distant for stereoscopic distance cues, even when there are no other cues in the visual field to serve as distance benchmarks. This mental model does not picture the sky in the shape of a hemisphere, but is more like a relatively shallow, inverted soup-bowl. When we view something on the horizon we perceive that it's located on a portion of the sky farther away than an object of the same real angular size at the zenith.
The important point of the argument is that our judgment starts with the stimulus of the retinal image of the moon, which is very nearly the same size for horizon moons or overhead moons. Stated in an equivalent way: The moon has nearly the same actual (physical) angular size wherever it is in the sky. So we mentally assume that an object of this retinal size lies on the perceptual sky dome. That dome is perceived as more distant at the horizon than overhead.
This is the same as saying, "What is our judgment of actual size of two things at different perceived distances, even though they have the same angular size?" The answer is that the one assumed nearer is judged to be smaller. This conclusion is consistent with the mental judgment that the horizon moon is farther from us.
This process supposedly operates even (especially) in the absence of any other visual cues. But the process is confused when we have our heads in an unusual position. This may be the result of our knowledge of the orientation of our head, from visual cues, and perhaps from information from the balance-sensing mechanisms of our inner ear. When there are competing sensory cues, our judgment of angular size can be altered by them, which may account for the confusing results of experiments designed to show that visual cues are the sole reason for the moon effect.
Any hypothesis that depends on a mental model of the sky requires that we have some way to know, at least approximately, which direction is "up". The illusion is "anchored" on our judgment of "up" and "down".
What's wrong with the sky-dome model as an explanation of the moon illusion?
One reader of an earlier version of this document mistakenly assumed I was promoting and defending the sky-dome model as an explanation of the moon illusion. That was not my intent at all, so I must increase the wordiness of this document by pointing out the obvious objection. Let me be very clear. The evidence for the illusion of the sky as an inverted soup-bowl is, in my view, abundant and undeniable, and must be dealt with if we are ever to understand the moon illusion. However, to use it as an explanation of the moon illusion is specious.
Consider an equally plausible argument using the sky-dome. We know that the full moon displays constancy of appearance (surface features) no matter where it is in the sky. It is the same moon wherever we see it. Few persons, when asked, would claim that the moon actually changes its physical size like a deflating balloon as it moves up in the sky. We adults agree that the moon has size constancy (children may not have formed such a conclusion). If we observe the moon in a starry sky, most persons say that the apparent distance of moon and surrounding stars is the same. There's no visual clue (such as parallax) to lead us to think otherwise. All of these "sky objects" are judged to be on this flattened "sky dome." If that is so, then the overhead moon should be judged larger in angular size, since it is on a portion of the sky that we judge is nearer to us.
Comparing these two hypotheses with their contradictory conclusions leads us to see the inadequacy of both of them, and the emptiness of this sort of argument. It forces us to examine just what we mean by "distance", "size", and "angular size". We will return to this point later. This confusion does not invalidate the perception of a flattened sky dome, but does reveal the dangers in trying to use one illusion (the sky dome) to explain another (the moon illusion).
I hate to suggest this, but many of the arguments about moon and sky illusions are similarly flawed, and seem only to be playing verbal games with the reader. They "sound good" but fall apart on close examination.
See A New Theory of the Moon Illusion for a satirical example of how a bogus explanation can seem quite plausible. Or is it bogus?
The flattened sky-dome hypothesis examined.
So why should we have this shallow-bowl model of the sky? Or, to put the question another way, why do we have a cognitive processing mechanism (however complex) that, in effect, gives us a perception of the sky distorted to conform to such a model? Two suggestions have been made. (1) The mechanism is hard-wired into our brains from birth. (2) The mechanism is built up through experience, by daylight sensory experiences, from a host of visual cues in everyday life.
Studies of children from age 4 to adult suggest that the moon illusion is present in children, and is stronger than it is in adults. It decreases in strength with age. [Liebowitz, H. and Hartman, T. "Magnitude of the Moon illusion as a Function of the Age of the Observer." Science, 130, 569-570.] This study was done indoors in a large darkened room (no other visual cues) with artificial moons at distances of 85 feet.
Studies with children can be confusing, for a child will often reach out to touch a distant object, like the moon on the horizon. Children haven't yet developed the same mental model of visual space that adults have. This study suggests that visual experience as one matures to adulthood modifies the illusion by improving our judgment of horizontal distances, thereby decreasing the illusion. This casts doubt on any explanations that assume that the moon illusion is a result of visual experience and suggests that the illusion itself may be innate and present at birth.
The hard-wired hypothesis supposes that natural selection has shaped those brain mechanisms that process and interpret sensory data, devoting more resources to those things that are important to survival. This results in brain resources being biased toward things seen in front of us, fewer resources to things overhead. Similar imbalance of perception details are present in animals.
Running great risk of over-simplifying a complex problem, we might say that things seen overhead appear smaller in angular size because our brain never evolved adequate resources to interpret data we judge to be "overhead". That data was not important to our species' survival. Our visual space allocates less detail and poorer judgment of relative distances for objects at large elevations up, or down.
Anisotropy of visual space.
Luneberg (1947) proposed a theory of vision that attempted to relate physical space with virtual (perceptual) space. He concluded that virtual space is non-Euclidean space of negative curvature: a hyperbolic space. Visual space does not have the same metric properties in all directions. (This idea is mentioned here for completeness, not to claim that Luneberg developed the idea fully and successfully, nor that he applied it to the moon illusion.)
This hypothesis is most helpful in understanding the fact that all lines of a set of physically parallel lines are also perceived as straight. Certainly they are not rendered straight on our retinas, and their curvature on the retina changes in complicated ways as we move our eyes right/left and up/down. Yet at any instant, they seem perceptually straight. Our brain is continually recalculating the data from the retinal image, to give a perception of straightness. Is our cognitive apparatus biased to render "straightness", or is this merely a by-product of cognitive processes that "correct" the "warped" retinal image to resolve visual contradictions when our eyes scan the real visual world? We live in a modern world with many straight and parallel lines: streets, walls, railroad tracks, etc. Yet the mechanism for dealing with the visual world evolved to its present form long before our ancestors ever experienced such geometric regularities. Clearly this process has more fundamental importance to our vision than rendering straight lines "correctly". I am not arguing that the curved retina is the reason for the anisotropy of visual space. I'm simply pointing out that the brain has mechanisms for dealing with the retinal shape, and the dynamically changing retinal image (as the eyes scan a scene), to produce a stable, and reasonably consistent geometry of visual space. This is what psychologicsts call "perceptual space".Once we recognize that visual space may not be anisotropic, and that it is a somewhat consistent distortion of real space, we have a new way of thinking about the moon illusion and related sky illusions.
Only when we scan our eyes around this geometric world, consciously trying to get the "bigger picture", do we become aware how our eye/brain mechanism handles this problem. Try this experiment. Look at a long straight wall. The wall seems to have straight and parallel lines when our line of sight is perpendicular to the wall. But when looking parallel to the wall, those same lines appear to be straight lines converging to a "vanishing point" on the horizon. Shifting our gaze from one end of the wall to the other we integrate all of these views and finally perceive that those parallel lines appear as curved lines diverging from a point at the horizon, becoming nearly parallel, then converging to a point at the other horizon. This is the geometric world of our wider visual field, one of curved lines, a "Remannian" space. But when we fix our gaze in one direction, our brain straightens out those curves, producing a result like the "Euclidean" space of an artist's strict perspective rendering.
The larger visual space.
Spherical perspective of parallel lines
perceived from wide-ranging sweeping of the eyes
over more than a whole hemisphere.
This is similar to a fish-eye lens photograph.
Z (zenith), N (nadir), V (left and right vanishing points).
The insets show how parallel lines are
rectified as straight in the smaller visual field.This process does not, however, consistently "correct" angles between lines. Right angles in a perspective drawing are usually not right angles on the paper or canvas. Nor are angles correctly perceived by the eye when the plane of the angle is tilted with respect to our line of sight.
Anyone can appreciate the character of this anisotropy by looking at the daylight cloud-covered sky in relatively flat terrain. Physically the cloud canopy is nearly a flat plane, as is the earth under our feet, because the radius of their curvature is so large compared the distance to the visual horizon. Think of observing the sky from a ship in the middle of an ocean. The ocean does appear nearly flat, but the cloud cover appears as an inverted shallow bowl. This shape can be appreciated even better if the observer slowly moves his eyes to scan around the horizon and up from horizon to zenith, with conscious intent to get a feeling for the shape of things in this larger visual space. Some people even perceive that the ocean curves somewhat upward toward the distant horizon just as the cloud cover curves downward. In any case, most people judge the sky at the horizon to be the same distance as the horizon.
A uniform cloud cover seems more like a flat roof than a spherical dome. We assume the cloud's average size is constant with distance. We see a linear decrease in the cloud's apparent sizes, just as expected for a flat surface. This visual cue dominates, for there are no others. Such vusual experiences form our mental model of the shape of the sky. [Photo by Fred Bucheit.] |
How does this impression square with the situation in real (physical) space? The physical distance to the most distant object one can see on the horizon depends on the elevation of the observer's eye above the ground. One can derive the formula for it, in terms of the earth's radius. For an eye elevation of six feet, the things we see on the horizon are actually about 3 miles away. Alto-cumulous clouds are about 2 to 3.5 miles overhead. So, physically, the distances horizontally and vertically are nearly the same, yet the overhead clouds seem much closer to most people than those near the horizon. This calculation may not seem quite fair, for we can see clouds that are physically well beyond the surface horizon, perhaps 10 miles away, due to their height above the earth surface. But can any reader and observer honestly claim that the clouds at the horizon seem farther away than the horizon? I've never found anyone who would make that claim.
Since the clouds seen "at" the horizon are about 10 miles away, the physical ceiling of a cloud-covered sky is a very flattened bowl (or saucer), 10 miles in radius and only about 3 miles high.
We have a strong impression that the cloud cover "joins" the horizon. Can this simply be that there's absolutely no visual cue to suggest that they are at different distances? Our brain may be making the simplest reconciliation of the situation where there are no visual clues to relative distance.
Why does the cloud cover appear to tilt downward at all? This is seen even when there are individual clouds with cues of shape, size, and shadowing. Beyond a certain distance, a distance set by other visual cues, our brain refuses to place objects at a greater apparent distance, especially if there are no local cues indicating objects between the horizon and the cloud cover. By "local" I mean, visually contiguous objects near the horizon line. Our cognitive mechanism seems to prioritize decisions, favoring reconciliation of "adjacent" cues at the expense of those displaced from one another by larger visual angles.
These facts illustrate that when we are dealing with these great distances, some of our usual geometric logic about distances is essentially useless to describe what we perceive. Once this fact of perception is realized, one also realizes that many of the experiments and theories of the moon and sky illusions and many of the published papers on the subject of visual illusions are simply irrelevant to explain our judgments of distances of very distant objects.
Why is visual space anisotropic? Specifically how does the anisotropy work? Why does the "metric" of this anisotropy shift in response to visual cues, such as objects at various distances in the field of view, and even on past visual experience? And why does some anisotropy remain even if nearly all visual distance cues are absent? Those are questions that need to be addressed. Little progress has been made in that direction. But we can't solve the moon and sky illusions until we deal with those questions.
The research clearly indicates that nearby objects in the field of view do influence our judgment of the distance and size of more distant objects. In a general way, it seems that
Even within the visual space of relatively unambiguous distances and sizes, our brain has placed objects in this space by resolving visual conflicts and by using some visual cues to modify and reinforce other cues.
Trehub's retinoid model.
Arnold Trehub, in his book The Cognitive Brain (MIT Press, 1991) proposed a comprehensive theoretical model of cognition, postulating neuronal mechanisms and systems that are responsible for cognition. He hypothesizes a neuronal structure that acts as a dynamic buffer for processing information from the retina, which he calls a retinoid. This retinoid performs many functions, some of which determine how visual sensory information is interpreted, before it is passed on to higher levels of visual processing. The retinoid organizes and integrates visual information into a unified model of visual space. Trehub calls it a "visual scratch pad" that stores spatially organized information as short-term memory.
One need not delve into the details of how this might work on the cellular level in order to recognize the importance of this general idea to the study of perception and to illusions of perception.
The visual process begins with sensory data, primarily from the retina. The retinal images represent a crude map (in two dimensions) of the real space of luminous points. The cognitive processes synthesize this data, reconciling ambiguities, correcting for deficiencies of the eyes themselves and creating a final "veridical" [1] image that we perceive as the space we are looking at. Past experience plays a role, when we observe familiar objects.
For example, we see three faces of a cube, but our experience with cubes generates a veridical judgment that the cube has six faces, including the ones that produce no retinal sensation until we rotate the cube. Our brains have established sub-processing systems for cubes, spheres, trees, and other familiar objects, treating them as entire objects even when we see them only partially.
The veridical image is in some ways better than the retinal images at any instant. Yet it can also have features that simply aren't an accurate representation of real space, as demonstrated by the many visual illusions studied by psychologists. Many such illusions have contradictory visual cues, and the brain does the best it can at reconciling those contradictions.
This cognitive bias of veridical space depends upon our prior cognitive judgment of up and down. We have a sub-processing brain mechanism for the space surrounding us. But the data funneled into this system has already subconsciously been realigned at an earlier stage of cognitive processing that made a judgment about up and down. Various cues, including our vestibular balance mechanism tell us at all times how our head is oriented. Then the rest of the cognitive apparatus further interprets visual cues based on this judgment of "up". [The older "sky dome" hypothesis depends upon this up/down judgment also.] Tilt of the head can slightly alter this judgment, but if there are enough cues, it won't destroy the sky and moon illusions. However, hanging by one's heels or looking at the sky with head inverted greatly reduces the illusion for many people. But this orientation also confuses one's interpretation of many visual spatial relationships. It's worth noting that the quality of many visual judgments is much reduced when viewing the world from this unusual position, even when viewing a picture or photograph that is also inverted. Things don't seem quite right. The quality of cognitive processing is severely degraded.
The moon illusion is consistent with what would be expected from evolutionary considerations. We have evolved cognitive processes that provide high quality visual information from nearby things, and things on our level that we can walk to and experience from various angles. These are all important to survival. Things seen high above, in the sky, or even those seen below, as when looking over the edge of a cliff, are less important. Therefore distance discrimination and detailed judgment of other visual properties of overhead objects is compromised.
The size-distance paradox.
Most people have a cognitive model that relates angular size to distance. This is called the "size-distance invariance law". When one observes two persons, one subtending a small angle, one a larger angle, one judges the person subtending the small angle to be more distant. This works for objects that we know or have already judged (from memory and other cues) to be "really" about the same size.
As usually seen, the sky-dome model "explains" the moon illusion in this manner: The retina receives a certain size stimulus, the same angular size for horizon or overhead moons. The brain has a model of the sky that causes us to judge that the overhead moon is the nearer one. Therefore since the two moon images have the same retinal size (stimulus), we judge the overhead moon to have smaller actual size. As indicated earlier, this over-simplified "explanation" seems to me empty and misleading.
Those who object to the "sky-dome" model in any of its variants point out that when subjects are asked which moon is larger, they answer "The horizon moon." When asked which moon is nearer, most will say "The horizon moon." This, critics say, contradicts the simple sky-dome explanation, and therefore invalidates it. They call this the "size-distance paradox". This objection, in my opinion, carries no weight. [I state again that I'm not a defender of the sky-dome "explanation" of the moon illusion, but just pointing out that some arguments against it are as weak as the model itself.]
In these discussions we must distinguish three levels of sensory processing that play a role in the final judgment.
What is the meaning of 'size'? When dealing with physical measuring instruments such as cameras and telescopes, the relations between angular size, linear size and distance is a straightforward application of trigonometry.
tan(angular size) = (linear size)/(distance)
Or tan(a ) = S/D
But visual judgments of linear size and distance are clearly confounded by visual illusion effects of various kinds. So "apparent linear size" and "apparent distance" were introduced, and the size-distance-invariance hypothesis was written:
tan(angular size) = (apparent linear size)/(apparent distance)
Or tan(a ) = S'/D'
On this view, if distance cues predominate, altering D to D', then the apparent size S' will be "computed" by the brain as necessary to interpret the angular size A of the image on the retina. But if size cues predominate (as when you are looking at a person whose size is familiar from long experience), the apparent distance D' will be computed by the brain.
This hypothesis has an underlying assumption: that the angular size of importance is simply the physical size of the retinal imagethe visual stimulus. But is it possible that perceived angular size is also independently subject to illusory effects? If so we should write:
tan(a ' ) = S'/D'
This view, and this equation, were first proposed by Don McCready [1965]. He developed this more fully in his [1985] paper, and applied it to the moon illusion [1986]. His website provides a very thorough presentation of these ideas.
This raises the question: What are we doing when we judge the "size" or "distance" of something (like the moon) for which we've had no experience close-up, and whose physical linear size and distance are too large to perceptually comprehend anyway? When we say a moon is "larger", are we talking about angular size or linear size?
Some argue that the basic moon illusion is one of angular size. Certainly all the experiments that ask subjects to compare the moon's image (or a simulated moon) with a physical object (or a simulated physical object) are asking for a comparison of perceived angular size. Also, the interpretation of experimental studies may be confounded by ambiguity of the meaning of the word "size", as understood by the subjects and by the experimenters. Even if the experimenter carefully explains to naive subjects the difference between angular size and linear size, and between "real" size and "perceived size", a subject may be incapable of making those distinctions when describing an observed object.
I will not belabor the three size equations given above, for they may not even be relevant to the question of the moon illusion. The moon illusion operates at real distances essentially infinite, and real sizes beyond direct apprehension. The only relevant variables are angular size, real and apparent. However we must admit that experimental studies of illusions seen in nearby space may help us understand the cognitive mechanisms that may also apply to the moon illusion.
Some studies have asked subjects "which moon seems nearer", which seems an unfair question, but still one cannot deny that we have mental processes that produce at least an approximate subconscious judgment of "near and far" for things in the sky, and this is certainly relevant to the sky illusions. The cognitive judgment of apparent angular size is made at a very early level of cognitive processing, without "thinking about it" consciously (deliberately). When asked which moon is larger, we then must consciously process this question (without being consciously aware of our previous unconscious determination of its apparent angular size).
Suppose an observer has subconsciously determined that the horizon moon has larger angular size than the zenith moon. This is the "perceived" angular size, a'. When asked which moon is nearer, the observer may consciously reason that the horizon moon must therefore be nearer. Never in this process is this observer aware of the unconscious process by which his brain already concluded that the horizon moon had larger angular size. No contradiction or paradox is present here, for these two levels of mental processing are not simultaneous. The contradiction comes only when we think about what we said.
Most visual illusions contain similar judgment contradictions. When the Penrose impossible tribar is seen, a subject may judge that the right side is more distant than the left, based on the way they connect at the top vertex. But then, looking at the constant angular width of the lower horizontal bar, the subject is forced to conclude that the two bottom corners are the same distance away. Contradiction. Yet each individual judgment seems "right" and is based on habitual visual associations of everyday experience. This is what makes illusions tantalizing.Observers schooled in physics and math, physicists, astronomers, and amateur sky-gazers, have learned somewhat different conscious models. When asked "Which moon is nearer?" they may respond "That's an unfair question; it's still the same moon, and in both cases the distance and size are too great to make a distance judgment." If a follow-up question is asked, "Which one seems nearer?" the answer is often "Well, you can't trust your eyes in such matters." Many scientists have learned (by their mistakes) not to trust their eyes in certain kinds of informal observations. As Helmholtz said, "I would never believe anything solely on the evidence of my eyes." Unlike Helmholtz, most physical scientists do not inquire into the reasons behind visual deceptions, they simply try to stick to observations and instruments that can be shown to produce reliable and observer-independent results.
Oculomotor micropsia and macropsia
Don McCready's web documents emphasize the importance of angular size illusions. He also proposes an explanation of the moon illusion based on angular size illusions due to oculomotor micropsia, an illusion that accompanies the accommodation of the eye lens and the convergence of the two eyes. Oculomotor micropsia has been known since it was discovered by Charles Wheatstone (1852), and has been amply demonstrated experimentally for nearby objects, those for which convergence and accommodation play a dominant role in perception of distance. McCready's detailed website document describes this effect quite well.
Briefly oculomotor micropsia is this: Normally, if there's only one object, or a dominant object, in the field of view, our eyes try to converge and accommodate to its distance. The muscles that control convergence and accommodation send signals to our brain, which are important distance cues. But when one's eyes converge and accommodate on a distance nearer than that of the object, that object appears to subtend a smaller angle than if one's eyes were converged and accommodated upon it. Micropsia means "appearing small", and here refers to the visual angle subtended by an object. The reverse effect, macropsia, occurs when the eyes converge or accommodate at a distance greater than the object being judged.
Why would the eyes converge or accommodate at distances different than the object of interest in the field of view? Several reasons. A very large number of nearby objects spread over the field of view may bias the brain towards convergence at their distance. For most people, the functions of convergence (aiming the eyes to a common point) and accommodation (focus setting of the eye's lenses) are "locked together" so if one converges to nearby objects, the accommodation adjusts to that distance also, and vice-versa.
Proponents of this hypothesis as explanation of the moon illusion argue that if there are a number of distant objects in the field of view, as there would be when observing the rising or setting full moon, the brain adjusts accommodation and convergence to them. But when viewing the full moon directly overhead, in a clear sky, there are no other distance cues, and the eye adjusts to its resting focus a distance of 1 or 2 meters. This makes the perceived angular size of the overhead moon seem smaller. Further support of this hypothesis is the effect of dark surroundings, which bias the eyes to adjust to the dark focus distance of about 1 meter.
But, these micropsia and macropsia illusions cause angular size differences of less than 10%, nowhere near large enough to account for the moon illusion seen by most persons.
Also, if accommodation were involved in the moon illusion, you'd think that elderly people who have lost nearly all accommodation should not perceive the illusion. Yet they do. Persons with eye lens implants have no accommodation, and they do perceive the moon illusion. Covering one eye removes convergence from consideration, but that doesn't make the moon illusion go away.
As usual in these matters it's not so simple. Experiments have shown that even when one eye is covered, or blind, the muscles and the eye lens still accommodate to the distance perceived by visual information supplied by the other eye. Also when the eye lens muscle is paralyzed in both eyes by use of atropine drops, micropsia still occurs. It seems that micropsia and macropsia are not the result of physical changes in the eyes, but are caused by processes occurring in the brain, the same processes that control the muscles of the eyes and the ciliary body that adjusts the focus of the eye lens.
Have you noticed that the moon, projected onto a planetarium dome with exactly the correct angular size, seems the same apparent size wherever it is located on the dome, and therefore appears "too small" when on the horizon, compared to our memory of the setting or rising moon in the real sky?
I've been informed (Jan 2000) that some researchers claim that the threshold for detecting depth due to retinal disparity is 1 arc second, so persons with normal vision can detect distance differences between the moon and objects up to at least 100 meters away. Such experiments are done under "ideal conditions" and usually involve judging whether two points of light are equally far away. My comments about the planetarium sky do not depend on the correctness of this figure, since the planetarium dome is clearly well within the range of stereoscopic vision, whichever figure you accept for the maximum distance for stereo vision.The hypothesis of the importance of eye-convergence (stereoscopic vision) in the moon illusion can be tested. Suppose we suppress stereoscopic cues in the planetarium by covering one eye. Experiments related to the moon illusion, especially those where nearby objects (nearer than about 50 feet) are in the field of view, should also be done with one-eyed viewing to suppress stereoscopic cues. This has not always been recognized as an important visual cue in these experiments. However, I think they play little role in the moon illusion itself, or any related illusion related to objects beyond the range of stereoscopic vision, except to establish the distance of nearby reference objects in the field of vision.
This illustrates why experimental psychology can be every bit as difficult as physics. As McCready says (August 1999): "Clearly, no theory has been fully accepted by the experts yet."
Donald Simanek
[2] This raises a question. What if we inverted the sky surrounding the moon when it is near the horizon? It wouldn't be hard to design a wide view binocular telescope with magnification equal to one, or a mirror system, that would do this. Has it been done? I haven't seen it reported in the literature. Looking at this inverted view, would observers perceive the moon illusion?
In this document I have not attempted to give a complete history of ideas about the moon illusion, nor have I tried to indicate in every case who first proposed a hypothesis or who did the experimental studies, or when. I had no intention to write a definitive history of the subject. Besides, it's often impossible to know who first had a particular idea, as distinct from who was first to publish it. Bart Borghuis' web document may be consulted for such details, and the anthology by Hershenson [1989] contains detailed review and bibliography of the literature of the subject.
Listing these web sites here does not constitute endorsement of the validity of all of their content. Many websites present only one or a few "explanations", without mentioning others. Some are a bit "crankish" in promoting a pet theory. From my perspective as a physicist, much of this seems like overkill in framing grand theories based on studies where there are too many counfounding variables, few data points, small sample size of subjects and often poor or ambiguous data.
Last edit June, 2010.
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Sugar Crisp Peanuts
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1 cup sugar 1/2 cup water 2 cups shelled raw peanuts
Mix sugar and water. Boil to dissolve sugar and add peanuts. Boil over medium heat until sugar crystalizes and there is no syrup left. Spread mixture on ungreased cookie sheet. Place in preheated oven at 350 degrees for 20 minutes, stirring every 5 minutes. Let cool.
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(CE:881a-881b) DAYR TASA, today the name of a Coptic village on the right bank of the Nile on the edge of the desert, south of ABNUB and opposite ABU TIJ. The cemetery and ancient church have been preserved. No ancient author mentions it. S. CLARKE in 1912 noted the church and its titular, the archangel Michael, in his list of the Coptic churches (1912, p. 217, no. 21). This church is an attractive modern four-column building probably of the late eighteenth century, with walled-up columns and stuccoed capitals. A little farther to the north some quarries fitted up as cells and containing Coptic inscriptions and a prayer niche are noted by G. Lefebvre (1908, p. 161). RENÉ-GEORGES COQUIN MAURICE MARTIN, S.J.
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FOR IMMEDIATE RELEASE July 18, 2012
Contact: HHS Press Office (202) 690-6343
Five goals align with Let's Move! pillars and promote healthy eating and active living on a local community level
Philadelphia, PA-- Secretary of Health and Human Services Kathleen Sebelius joined First Lady Michelle Obama and local officials from across the country to announce the next chapter in the Let's Move! Cities, Towns, and Counties program, which encourages local elected officials to focus on improving the health of their communities.
Secretary Sebelius announced five goals for local officials to achieve within the next year to address obesity and help communities be healthier. These goals align with Let's Move!'s five basic pillars.
"Make no mistake, childhood obesity is a national problem and demands everyone's attention. But it's a problem that can't be solved just at the national level. We can make a significant impact, city by city, town by town, county by county," Secretary Sebelius said.
The five goals and corresponding Let's Move! pillars are:
Goal: Start Early, Start Smart: To provide children with a healthier start, local elected officials commit to helping early care and education program providers incorporate best practices for nutrition, physical activity and screen time into their programs. (aligns with Pillar One – Creating a healthy start for children)
Goal: My Plate, My Place: To empower parents and caregivers, local elected officials commit to prominently displaying My Plate in all municipal or county venues where food is served. (aligns with Pillar Two – Empowering parents and caregivers)
Goal: Smart Serving for Students: To provide healthy food in schools, local elected officials commit to increasing participation in the School Breakfast Program and the National School Lunch Program. (aligns with Pillar Three: Providing healthy food in schools)
Goal: Model Food Service: To improve access to healthy, affordable foods, local elected officials commit to implementing healthy and sustainable food service guidelines that are aligned with the Dietary Guidelines for Americans in all municipal and county venues that serve food. (aligns with Pillar Four: Improving access to healthy, affordable foods)
Goal: Active Kids at Play: To increase physical activity, local elected officials commit to mapping local playspaces, completing a needs assessment, developing an action plan and launching a minimum of three proven policies, programs or initiatives aimed at increasing access to play. (aligns with Pillar Five: Increasing physical activity)
Secretary Sebelius also announced public and private sector commitments to support the goals of Let's Move!:
Note: All HHS news releases, fact sheets and other press materials are available at http://www.hhs.gov/news.
Like HHS on Facebook , follow HHS on Twitter @HHSgov , and sign up for HHS Email Updates.
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Keep a calendar on your desktop with Interactive Calendar
Not that very long ago a desktop calendar was a big paper thing that sat on top of your desk (sometimes under your typewriter). Now it's typically a piece of software like Interactive Calendar. This attractive program makes it easy to view a calendar on your computer desktop and keep detailed records of upcoming events. We think it's a nice option if you want something more comprehensive than the built-in Windows calendar but don't want to use the calendar that's integrated into your e-mail client.
Interactive Calendar has a sleek, customizable interface. The calendar is meant … Read more


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The roster of dogs at the Meeker Classic Championship Sheepdog Trials boasts a variety of backgrounds and circumstances. Be it that they hail from all parts of the world, descend from a long line of proven dogs or just possess an innate instinct to gather and move stock — each will face the same challenge as they walk onto the field at Meeker.
This year when Angie Coker Sells and her dog Quill walk out on the field it will be a homecoming of sorts. Their story started four years ago during the 2009 Meeker Classic. Be it fate or destiny, a unique set of circumstances and people were set in motion that week of the Meeker Classic. Angie, a Meeker Classic champion in 1999, was the judge for the 2009 Meeker Classic and Elaine Wood was volunteering at Meeker with the humane society rescue rig.
Quill, as a pup, and face covered with porcupine quills, showed up at the 2009 Meeker Classic.
Travelling back to Meeker with Elaine, he spent the rest of the Meeker Classic hanging out at the trial field with Elaine and making friends wherever he went. Elaine and others checked in with local ranchers to see if anyone recognized the dog or claimed ownership. He had a collar but no tags. Several people came by to see Quill but, unfortunately, none recognized him or had any idea who he might belong to. By the end of the trial, no one had stepped forward to take responsibility for Quill, and Elaine had become attached to the sweet, gentle pup. She decided to take him home with her to Greeley.
Over the next several weeks porcupine quills that had been embedded under the skin continued to migrate their way out. One came out from behind his eye and several came out the top of his nose. Two additional trips to the veterinarian necessitated sedation to remove a couple hundred more quills. During all of this Quill never lost his sweet nature and was Elaine's constant shadow, quickly becoming a favorite at the veterinarian's office.
Months later, having recuperated from the porcupine quills, Quill was showing a natural inclination to work sheep. Elaine wanted to see if Quill might have what it takes to become a sheep dog. Angie Coker Sells had helped train most of Elaine's border collies, so in 2010 she sent Quill to Angie in Tecumseh, Okla., for training.
Angie and Quill hit it off right away. Angie could see Quill's natural talent and Quill took to life on the ranch. Because Quill was a fast learner and had plenty of grit, Angie also had to keep an eye on him, manage his energy and direct his instinct. It wasn't long before Angie called Elaine asking if she might be interested or willing to let her keep Quill. He had all the makings of a great ranch dog for what Angie needed. Though she wasn't trialing at the time, she also knew he'd be a good candidate if she ever did.
It was a hard decision for Elaine. Having rescued Quill and rehabilitated him, she knew that living in town and working sheep on an occasional basis would be a hard transition for Quill to make. After lots of thought she decided what was best for Quill, knowing he was much better off in a home where he had a real job to do.
Quill took to working stock naturally.
Quill loves to ride the four-wheeler with Angie — it usually means there's work to be done!
Who would have guessed that the young, stray border collie, covered in porcupine quills, would make the full circle and come back to compete where he showed up in such need of help? Win, lose or draw Angie and Elaine are thrilled he'll be back this year. You can watch Quill run Thursday afternoon, Sept. 5, at the 27th annual Meeker Classic.
For information, visit www.meekersheepdog.com.
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840 nm SLEDs Conform to Bellcor Standard
April 2, 2008 11:44 am | CommentsAMS Technologies introduced EXALOS AG's line of 840 nm superluminescent light emitting diodes (SLEDs) that typically exhibit 5 mW of optical power in a single mode fiber and a 48 nm, 3 dB spectral bandwidth. The standard light sources are delivered in a 14-pin butterfly housing with a monitor diode and a fixed connection/angled physical contact connector. The parts conform to the Bellcor GR-468-CORE standard, and they can be integrated into OCT systems, data transfer units and fiber optic sensors for civil structure monitoring as well as for aerospace navigation.
Fine Binning for White LEDs Delivers Improvements
April 2, 2008 11:37 am | CommentsSRAM Opto Semiconductors introduced its advanced fine binning for white LEDs that delivers improvements in off-angle color uniformity as well as a typical color rendering index (CRI) of 80+. This advanced binning process for white LEDs corresponds to a 3-step McAdams ellipse, and it is available for Power TOPLED, Advanced Power TOPLED and the proprietary DRAGON family of products. Applications such as backlighting of diffused surfaces and linear array applications benefit from the uniform light enabled by this technology which is fully ANSI/Energy Star-compliant in the United States.
QVGA Modules Feature a Touchscreen Option
April 2, 2008 11:31 am | CommentsPhoenix Display International (PDI), Inc. introduced its line of 5.7" monochrome QVGA modules that are available in FSTN/gray/positive/transflective or STN/blue/negative/transmissive configurations. These graphic modules (PN G-320240-5.7) allow the user to control each pixel individually to display both text and graphics simultaneously. With a variety of options available, the monochrome graphic displays are modular in design, and they can be customized to fit specific applications. Both the STN and FSTN models are available with an RA8803 controller with built-in touchscreen controller, and they can be configured with either a CCFL or LED backlight.
HV Nonmagnetic Variable Trimmer Capacitor Works at Cryogenic Temperatures
April 2, 2008 10:52 am | CommentsFeaturing high purity ceramic dielectrics, the SGNM series of high voltage nonmagnetic variable capacitors from Sprague-Goodman Electronics can be sealed to 40 lbf/in2 (276 kPa), or used for cryogenic applications as low as 4K. DC working voltage ranges from 1.5 kV up to 7.5 kV (DC withstanding voltage from 3 kV to 15 kV). Capacitance ranges start with 1 – 10 pF, and increase (in 5 pF increments) to 10-180 pF. The capacitors
Constant Current LED Driver Detects Dark Pixels In Real Time
April 2, 2008 10:29 am | CommentsMacroblock's MBI5039, aimed at LED panel applications, offers real-time error detection of the full LED panel, helps designers to detect dark pixel errors. This 16-channel constant current LED driver supports constant output current from 3 mA to 90 mA and sustains up to 17V at the output ports. The clock frequency
InGaN White LEDs Perform in General Lighting Applications
April 2, 2008 10:07 am | CommentsAllegro Microsystems, Inc. announced its series of white multi-chip LEDs that provide a range of high-powered InGaN white LEDs that can be used in general lighting applications, amusement and gaming equipment, and for backlighting TFT displays. Each module combines either six or eight LEDs in one to four separate channels. Modular design allows the SEPW devices to be assembled into string arrays by connecting the modules in a series.
Custom, DC Gearmotors with Cut Steel Gears for High Strength
April 2, 2008 10:03 am | CommentsLow cost DC gearmotors for OEM applications are available from Source Engineering, Inc. These 12 mm to 50 mm DC gearmotors are available with cut steel gears for high strength applications, plastic gears for low noise requirements, and low cost, powered metal. Available in ratios from 5:1 up to 3000:1, these low cost DC Brush type gearmotors are appropriate for pick-and-place, medical testing equipment, robotics, toys and games, valve and door actuation, ROV (Remotely Operated Vehicle) fin and steering actuators, appliances, manufacturing, security applications, and assembly operations. The inline and offset output shafts of the gearmotors can be custom machined with cross holes, splines, keyways, and flats, or end drilled and tapped.
Front End/Rectifier Touts High Frequency at Light Loads
April 2, 2008 10:02 am | CommentsCherokee International announced its 2,500W CAR2512 front end intended for low profile, 12V distributed power architecture applications such as high-performance enterprise and service-provider switches and routers, mid- to high-end servers and storage equipment.
Brush DC Motors Feature Quiet Operation
April 2, 2008 9:53 am | CommentsAMETEK Technical and Industrial Products introduced the PITTMAN Series 9000 brush-commutated DC motors that deliver quiet and smooth operation for equipment used in data storage, medical/biotech, semiconductor processing and automation applications. Their modular construction promotes customization to satisfy specific requirements. These motors, with 2-pole stators, incorporate 7-slot skewed armatures to minimize magnetic cogging (or reluctance torque), and they enable smooth and quiet running performance. Commutators are diamond-turned after armature assembly to ensure optimum concentricity and long brush life. Windings are resin-impregnated for greater reliability in incremental motion applications. Standard features include ceramic magnets, silicon steel laminations, copper graphite brushes and heavy-gauge steel housing. Speed, voltage, current and torque characteristics can be varied to meet application demands.
Electronic Timer Relays Perform in Universal Applications
April 2, 2008 9:46 am | CommentsPhoenix Contact introduced its family of electronic timer relays (ETDs) that offer a range of timing settings and other practical functions. Featuring easy set-up and diagnostics, the ETDs are appropriate for use in universal applications. They monitor different time functions without using complicated controllers. The timer relays can be adjusted to an array of timing settings ranging from milliseconds through several days. ETD devices equipped with special functions, including star/delta (or Wye/Delta) and watchdog, are also available.
8-port PoE Midspan Allows Remote Monitoring
April 2, 2008 7:34 am | Phihong | CommentsFully compliant with the IEEE802.3af power-over-Ethernet (PoE) standard for detection, disconnect, and voltage control, the POE125U 8-port midspan from Phihong enables remote monitoring for single points of backup in applications such as small office environments, wireless access points, and IP cameras for security applications. The SNMP-capable Gigabit-compatible 8.9" × 7.8" × 1.75" device provides up to 15.4W of power per port
LowProfile SMD Board to FPC Connector with 0.4 mm Pitch Dual Row Contacts
April 2, 2008 6:59 am | CommentsSuitable for use in handheld electronics, Omron Electronic Components RoHS compliant XB4A (plug) and XB4B (socket) series of 0.4 mm (0.016") pitch SMD board to FPC plug and socket connectors have a stacking height of 0.9 mm (0.035") and a width of 4.1 mm (0.161") or 5.0 mm (0.20"), including the solder terminals, when mated. Their high reliability double contact point gold plated contacts are resistant to improper contact alignment and
Low-Profile Transformer Suits Military Applications
April 2, 2008 6:29 am | CommentsProvided in both SMT and through-hole configurations, the LVB-4203 MIL-STD-1553 data bus transformer from Beta Transformer Technology is intended for use with 3.3V transceivers in military and other high-reliability applications. The transformer has a low profile of 0.130" height with a 0.625" × 0.625" footprint.
Round Rocker Switches Offer Multiple Functions
April 2, 2008 6:16 am | CommentsA snap-in fit for a 20 mm panel hole, Phaseda's single-pole RL3-5 round rocker switch is configurable as a SPST or SPDT device and the double-pole RL3-4R rocker switch offers DPST functionality. The switches can handle a UL-approved 16A or 1/3HP at 125V AC for high power and motor applications, and 10A at 125V AC for small appliances and normal usage with cUL and VDE approvals, and are RoHS compliant.
Digital Potentiometer IC Provides Simple Up/Down Control
April 2, 2008 5:48 am | CommentsWell-suited for control and calibration applications such as digital volume control and display adjustment applications in portable, consumer, and industrial electronic products, the CAT5128 digital potentiometer IC from Catalyst Semiconductor is a volatile, single-pot device with up/down control to provide a simple digital interface. Housed in an 8-lead SOT-23 package, the device powers on at the midscale setting and provides a 32-position linear taper