DISSOCIATION OF PROCESSES UNDERLYING SPATIAL S-R COMPATIBILITY - EVIDENCE FOR THE INDEPENDENT INFLUENCE OF WHAT AND WHERE

The process-dissociation procedure was used to estimate the influence of spatial and form-based processing in the Simon task. Subjects made manual (left/right) responses to the direction of arrows (> or <) pres ented to the left or right of fixation. Manipulating the proportion of incongruent trials (e.g., a right-pointing arrow presented to the lef t of fixation) affected both the size and direction of the Simon effec t. To account for this pattern of data, we compared process estimates based on three possible relationships between spatial and form-based p rocessing: independence, redundancy, and exclusivity. The independence model provided the best account of the data. Most telling was that in dependent form-based estimates were superior at predicting observed pe rformance on arrows presented at fixation and did so consistently acro ss conditions (r's > .80). The results provide evidence that the form (''what'') and spatial location (''where'') of a single stimulus can h ave functionally independent effects on performance. They also indicat e the existence of two kinds of automaticity-an associative (''implici t learning'') component that reflects prior S-R mappings and a nonasso ciative component that reflects the correspondence between stimulus an d response codes. (C) 1995 Academic Press, Inc.