van gompel et al . ( 2005 ) explain their data in terms of a special type of reanalysis model called the unrestricted race model . in case of ambiguous input , the parser is assumed to explore , in parallel , all possible analyses of the new input word . the parser may be biased in favor of one or more of the alternative analyses due to prior syntactic as well as non - syntactic information , to syntactic complexity , or otherwise . the prior information includes the meaning computed for the input string up to and including the input word that was processed last . the parser adopts the analysis that finishes first , i.e. , wins the speed race , and discards all other ones . if subsequent words can not be assigned a satisfactory or plausible analysis , the parser is forced to backtrack and to reanalyze ( part of ) the input string . the model is a syntax - first model because the initial analysis of a novel input word does not take the meaning of this word into account but only its part - of - speech ( major word - class ) feature . ( however , as said before , any biases resulting from prior syntactic and non - syntactic information are supposed to make themselves felt here . ) the sentence materials the participants in van gompel et al.s experiments had to read in the ga condition , had been carefully prepared so as to exclude a strong a priori preference for a low or high attachment interpretation . this implies that the processor settles on attaching the verb of the relative clause high and low with roughly equal proportions : the two attachments win the race about equally often . as they both yield a plausible meaning , no reanalysis needs to be carried out . in the two la conditions , however , when the meaning of the verb is accessed and integrated with the meaning of the current input string ( e.g. , province - retiring ) , the parser s initial attachment site for the verb of the relative clause turns out to be wrong in about half the trials . hence , reanalysis will occur in roughly 50% of the trials and manifest itself in prolonged reading times due to  among other things  a higher incidence of regressive eye - movements ( eye fixations on earlier text regions ; regressions for short ) . the unrestricted race model is not the only possible interpretation . consider a slightly but essentially  different version where the syntactic processor is operating in parallel with the non - syntactic processors ( cf . jackendoff ( 2002 ) and kuperberg ( 2007 ) ) . specifically , the syntax - first assumption of the unrestricted race model is dropped and the syntactic races for an attachment site of a new ambiguous input word proceed in parallel with the construction of a plausible conceptual interpretation . the conceptual processor can work in a manner similar to the syntactic processor , except that its decisions are founded on conceptual rather than syntactic constraints and preferences . the conceptual constraints derive from the meanings of the content words , and from the meaning implications entailed by inflections and function words ( e.g. , the genitive morpheme attached to governor in the governor s province and the function word of in the province of the governor are both interpretable as expressing a possessive relationship ) . thus , the conceptual processor builds its own hierarchical representation of the current input sentence in parallel to the syntactic representation . in simple cases ( e.g. , the dog bit the man ) , the first conceptual representation that the conceptual processor proposes without having taken syntactic information into account , will dovetail with the first syntactic representation proposed by the syntactic processor . if in more complex cases , such as the dog was bitten by the man , the preferred conceptual analysis happens to conflict with the preferred syntactic parse ( cf . ferreira ( 2003 ) ) , a revision will have to be negotiated between the parallel processors . in terms of the la examples ( 2 ) and ( 3 ) , the conceptual processor quickly determines that governor , but not province , is a plausible actor of retire events . simultaneously with this conceptual analysis , the race for high versus low attachment of retiring takes place within the syntactic processor . after both the syntactic and conceptual processors have finished , a comparison stage follows which checks whether the output structures they produced are compatible . in the two la - conditions , the predictions from this parallelized version of the unrestricted race model coincide with those of the original serial version : in the ga condition , the probability of a mismatch is zero . a second option adds interactivity between syntactic and non - syntactic processing but drops the separate comparison stage . for the sake of simplicity , let us restrict ourselves to two processors  one syntactic , one conceptual  which are dealing with syntactically and conceptually correct input sentences . the first two about how the processors inform one another , the last one about how eye - movements respond to reanalysis : 
 whenever a decision has been made by one of the linguistic processors , it is immediately communicated to the other one.a processor that is informed about a decision reached by the other one , immediately checks whether it is compatible with ( one of ) the option(s ) allowed by the current internal state , and discards incompatible options.if , after terminating its work on the current input , a processor is left without acceptable analyses , it initiates reanalysis , which may cause regressive eye movements . whenever a decision has been made by one of the linguistic processors a processor that is informed about a decision reached by the other one , immediately checks whether it is compatible with ( one of ) the option(s ) allowed by the current internal state , and discards incompatible options . if , after terminating its work on the current input , a processor is left without acceptable analyses , it initiates reanalysis , which may cause regressive eye movements . what does this entail with respect to the ga and la sentences ( 1 ) through ( 3 ) ? there are two possibilities  the conceptual processor reaching a decision prior to the syntactic processor ( i.e. , it settles on a conceptual attachment without being informed by syntactic information ) , or vice - versa . suppose that  for whatever reason  the conceptual processor decides to select governor as the actor of retire , and that this decision reaches the syntactic processor prior to the latter having chosen an attachment site for the relative clause . the syntactic processor then easily verifies that this conceptual choice corresponds to a low attachment site , and immediately adopts this decision , which fits the current syntactic tree . the same final conclusion follows when the conceptual processor prefers bodyguard as the actor of retiring . in cases where the syntactic processor manages to take an attachment decision before the conceptual processor makes its choice if the conceptual processor reaches its conclusion ahead of the syntactic processor , the latter will never fail to accommodate this conclusion because the corresponding attachment site is always available . conversely , if syntactic processing terminates prior to conceptual processing , it may have selected an attachment site that the conceptual processor refuses to adopt  e.g . , interpreting province as the actor of retiring how does the model proposed in this section differ from the constraint - based parallelinteractive models targeted by van gompel et al . first of all , in current constraint - based models , the processors (  information sources  ) can not initialize reanalysis individually . instead , the information recruited by these sources is pooled together (  integrated  ) and eye movements are affected only after an overall decision has been reached . the second aspect concerns the decision - making mechanism itself , which is based on competition between alternative analyses . if the pooled information clearly supports one of the alternative analyses to the detriment of the other one(s ) , the winner will emerge sooner than when the evidence is mixed . . found ( but see the unexpected computer simulation results reported by green and mitchell 20061 ) . however , the model outlined in the present section shows that parallelism of syntactic and conceptual processing can be realized in a model where two ( or more ) concurrent processors are engaged in a race to be the first to complete their jobs . this speed race model is faithful to van gompel et al.s ( 2005 ) empirical findings while lacking the  monolithic  pooling of syntactic and conceptual information typical of existing constraint - based models . the answer is negative : there may very well be competition within each ( or some ) of the linguistic processors . for instance , the selection of a suitable attachment site for the verb retiring within the syntactic parser could involve competition instead of a speed race . specifically , instead of constructing two or more independent parse trees for a syntactically ambiguous input string ( as happens in the unrestricted race model ) , in a competition model an incoming word or word group is tentatively and temporarily attached to all nodes of the current tree that are allowed by the grammar . the ensuing competion between alternative attachment sites is then resolved on the basis of factors such as the frequency or the complexity of the resulting syntactic configurations , the recency of the nodes to which the new input is attached , or their activation level . the details of the mechanism subserving competition within the syntactic processor need not concern us here . specific proposals have been made by , e.g. , stevenson ( 1993 , 1994 ) , kempen and vosse ( 1989 ) and vosse and kempen ( 2000 ) . similarly , within the conceptual processor there may be a competition for the selection of the role of actor of the retire concept . ( 2005 ) do not qualify as  evidence against competition during syntactic ambiguity resolution . at best , their data count as evidence against the monolithic type of competition operating in current constraint - based models . modularized ,  less monolithic version of a parallel - interactive speed race model of ambiguity resolution accounts for the eye tracking facts . competition can play an important role in such a model if it is positioned within the individual syntactic and conceptual processors .
in a recent series of publications ( traxler et al . j 
 mem lang 39:55892 , 1998 ; van gompel et al . 
 j mem lang 52:28407 , 2005 ; see also van gompel et al . 
 ( in : kennedy , et al.(eds ) reading as a perceptual process , oxford , elsevier pp 62148 , 2000 ) ; van gompel et al . 
 j mem lang 45:22558 , 2001 ) eye tracking data are reported showing that globally ambiguous ( ga ) sentences are read faster than locally ambiguous ( la ) counterparts . 
 they argue that these data rule out  constraint - basedmodels where syntactic and conceptual processors operate concurrently and syntactic ambiguity resolution is accomplished by competition . 
 such models predict the opposite pattern of reading times 
 . however , this argument against competition is valid only in conjunction with two standard assumptions in current constraint - based models of sentence comprehension : ( 1 ) that syntactic competitions ( e.g. , which is the best attachment site of the incoming constituent ? ) are pooled together with conceptual competitions ( e.g. , which attachment site entails the most plausible meaning ? ) , and ( 2 ) that the duration of a competition is a function of the overall ( pooled ) quality score obtained by each competitor . 
 we argue that it is not necessary to abandon competition as a successful basis for explaining parsing phenomena and that the above - mentioned reading time data can be accounted for by a parallel - interactive model with conceptual and syntactic processors that do not pool their quality scores together . within the individual linguistic modules , decision - making 
 can very well be competition - based .