You Can't Have It Both Ways: An Examination of Congruency Effects in Task Switching.

Abstract

Environmental contexts help us set relevant goals and guide appropriate behaviors. In situations in which a single stimulus affords multiple responses, cognitive control processes allow us to establish the appropriate goal based on the present context and activate rules associated with the current goal. This enables execution of correct responses, even when those responses are inconsistent with alternative responses afforded by the same stimulus. The experiments in this dissertation use task-switching paradigms to examine how individuals respond to situations in which a single stimulus can afford two responses. These behavioral studies examine congruency effects, the performance differences between congruent trials, for which the same response is always appropriate, and incongruent trials, for which the appropriate response differs depending on the currently-relevant task. Experiments 1 and 2 examine the possibility that congruency effects observed in task switching are fundamentally similar to congruency effects in Stroop paradigms by comparing task-switching congruency effects in conditions with and without Stroop-like interference. In both experiments, congruency effects in task switching interact with Stroop-like congruency effects, suggesting a common mechanism. Based on the results in Experiments 1 and 2, I suggest that automatic activation of a category by attributes of the stimulus that have previously been relevant underlies congruency effects in Stroop and task-switching situations. This hypothesis is supported by findings in Experiments 3 and 4 that task-switching congruency effects are absent for conditions in which a stimulus is never assigned to different categories on different trials. Congruency effects across these paradigms can be accounted for by a generalized model of competition driven by repeated assignment of stimuli to competing categories.