effet du nombre des graphèmes en Anglais - Aix Marseille Université
effet du nombre des graphèmes en Anglais - Aix Marseille Université
effet du nombre des graphèmes en Anglais - Aix Marseille Université
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234App<strong>en</strong>dice IFigure 6 gives an illustration of what one might call the "phonemic" space in the MROM-P. It showsactivation functions of the phonological units at the onset, nucleus and codas positions obtained for the targetword "BLUE".PARAMETER TUNING. In our parameter tuning approach, we also followed the stratagem of nested modeling.Since this demands that MROM is an integral part of MROM-P, we faced the problem of having tofind new parameters for the phonological substructures of the model, while keeping the original parametersof MROM as constant as possible. However, because adding new interactive substructures to the originalIAM leads to a new global dynamical system, the original parameter set had to be adjusted (the old one leadto catastrophic model behavior). Table 3 gives the parameter set fixed for the pres<strong>en</strong>t simulation studies onthe basis of the parameter tuning studies discussed below. We acknowledge that more work has to be done inorder to precisely determine the role of each parameter for the model dynamics. Furthermore, althoughconnectionist modelers in g<strong>en</strong>eral seem to ignore the issue, we acknowledge that a c<strong>en</strong>tral aim for futurework in the field must be to solve the nontrivial problem of the id<strong>en</strong>tifiability of complex A-type models ing<strong>en</strong>eral, and models of the IA family, in particular.SIMULATION METHOD. In the following studies, we simulate effects obtained in the LDT. Because thetask-specific mechanisms of the LDT have well be<strong>en</strong> specified in the MROM (Grainger & Jacobs, 1996),the same <strong>des</strong>ign principles (i.e., principles that determine the behavior of a class of models and the observeddep<strong>en</strong>d<strong>en</strong>t variables) were adopted here. However, giv<strong>en</strong> that the pres<strong>en</strong>t version of MROM-P is still prototypical-implying that the pres<strong>en</strong>t study provi<strong>des</strong> no criteria-ori<strong>en</strong>ted falsification test of the MROM-P, butrather a test of its appropriat<strong>en</strong>ess as a "working model" of phonological coding- (see discussion section), wedid not carry out full-blown simulations. This would have necessitated, for example, use of stochastic responsethresholds and of a large number of simulated subjects equal to the number of subjects in the realexperim<strong>en</strong>ts (Grainger & Jacobs, 1996). Consequ<strong>en</strong>tly, rather than response (time) distributions, we simplyobtained activation functions for each item used in the simulated experim<strong>en</strong>ts. For each experim<strong>en</strong>tal condition,the mean of these activation functions was calculated across the differ<strong>en</strong>t items. The resulting activationfunctions (and derived mean RT bar charts) are pres<strong>en</strong>ted as illustrations of how the model can quantitativelyaccount for the experim<strong>en</strong>tal data./u/1/bl/1ACTIVATION0.50/sl//pl//kl//gl/ /fl/2030ACTIVATION0.50/ju//$//5/2030403020ONSET NUMBER100010CYCLES403020NUCLEUS NUMBER100010CYCLES1/*/ACTIVATION0.50/ls//l//g/2030403020CODA NUMBER100010CYCLESFigure 6 : Activation functions of phonological units at the onset, nucleus and coda positions obtained for thetarget word "BLUE".Concerning the task-specific read-out proce<strong>du</strong>re, the MROM-P follows the <strong>des</strong>ign principle of theMROM in that "No" responses are pro<strong>du</strong>ced by monitoring the global orthographic activity g<strong>en</strong>erated by thestimuli, and "Yes" responses are g<strong>en</strong>erated by looking at the orthographic unit activity (for simplicity, wedid not consider the possible role of global orthographic activity on "Yes" trials here ; cf. Figure 3 above).The rationale for this is giv<strong>en</strong> in Ferrand and Grainger (1996) who discuss the qualitative predictions ofMROM-P for a masked priming LDT. In accord with the assumptions of Grainger and Jacobs (1996), theresults of Ferrand and Grainger suggest that in an LDT using pseudohomophones, participants use read-outfrom the orthographic lexicon, because read-out from the phonologic lexicon would lead to too many falsepositive errors.