The Effects of Practice on the Dissociation Between Task Switching and Inhibition.

Abstract:
Recently there has been great interest in defining executive control in terms of its component processes. Two candidates for such processes are task switching and inhibition. Neuroimaging studies suggest that both of these processes may be mediated by a common mechanism localized in the dorsolateral prefrontal cortex. In order to compare the two processes directly, participants performed an experiment with both task switching and inhibition demands. Participants kept cumulative counts of left and right arrows while responding to the arrows with key presses. Alternating the active count by presenting left and right arrows induced task switching. Key presses incompatible with the direction of the arrow induced inhibitory processes. The goal of this study was to determine whether or not these processes recruit a common mechanism. Following Sternberg's additive-factors rationale, it was predicted that if the processes were independent, a simple additive effect of compatible/incompatible stimulus-response mapping on task switching would be observed. However, if the two processes were dependent on a common mechanism, then the effect would be overadditive. Results show that although there is an overall interaction between task switching and inhibition, this interaction declines with practice across the experiment. This suggests that early in the experiment, task switching and inhibition depend on a common mechanism, but that later in the experiment these processes become independent.