Evaluation of mental representation for same and mixed compatibility assignments.

In most studies of stimulus-response (S-R) compatibility, assignments within a set are either compatible or incompatible for all S-R combinations. The present study provided an extension of previous research by examining the situations with same or mixed S-R assignments for pairs of subsets from a four-choice spatial precuing task. Assignments of stimuli to responses for the subsets could be same (both subsets assigned compatibility or both assigned incompatibility) or mixed (one subset assigned compatibility and one subset assigned incompatibility). A precue stimulus provided advanced information about which subset, and thus which assignment, would be required for responding on each trial. Experiment 1 had four visual stimuli assigned to four response locations, whereas Experiment 2 had the four visual stimuli assigned to only two response locations. For both experiments, the analyses revealed similar patterns of reaction times, with reaction times slower in the mixed condition than in the same condition. Moreover, the reaction times for the compatible assignments in the mixed sets were slowed more than the incompatible ones in those sets. The nonprecued subset influenced the S-R translation processes, indicating that the nonprecued subset was part of the mental representation upon which subjects were making decisions.