AN INTERACTIVE ACTIVATION APPROACH TO OBJECT PROCESSING - EFFECTS OF STRUCTURAL SIMILARITY, NAME FREQUENCY, AND TASK IN NORMALITY AND PATHOLOGY

We present a computational model of the processes involved in retrievi ng stored semantic and name information from objects, using a simple i nteractive activation and competition architecture. We simulate eviden ce showing a cross-over in normal reaction times to make semantic clas sification and identification responses to objects from categories wit h either structurally similar or structurally dissimilar exemplars, an d that identification times to objects from these two different classe s correlate differentially with measures of the structural similarity of objects within the category and the frequency of the object's name. Structural similarity exerts a negative effect on object decision as well as naming, though this effect is larger on naming. Also, on namin g, structural similarity interacts with the effects of name frequency, captured in the model by varying the weight on connections from seman tic to name units; frequency effects are larger with structurally diss imilar items. In addition, (1) the range of potential errors for objec ts from these two classes, when responses are elicited before activati on reached a stable state, differ-a wider range of errors occur to obj ects from categories with structurally similar exemplars; and (2) simu lated lesions to different locations within the model produce selectiv e impairments to identification but not to semantic classification res ponses to objects from categories with structurally similar exemplars. We discuss the results in relation to data on visual object processin g in both normality and pathology.