Tailoring perception and action to the task at hand

Two experiments investigated whether and how task demands affect the way perceptual events and actions are cognitively represented, and how this affects performance. Subjects performed two-dimensional Simon tasks that alternated with, or were embedded into, a logically unrelated ‘‘priming task’’, in which the relevance of horizontal and vertical dimensions varied frequently. Making the horizontal dimension relevant in the priming task increased the horizontal Simon effect, and making the vertical dimension relevant increased the vertical Simon effect. These findings suggest that stimulus and response representations are not invariant but are tailored to the current task demands. This has implications for models of perception and action planning, stimulus response compatibility, and executive control.