Two measures of task-specific inhibition

Abstract

Inhibition has been implicated as an important mechanism for task-set control, ensuring the efficient selection of the to-be-performed task over alternative possibilities. Across three experiments we demonstrated the effects of two potentially different types of task inhibition. The first is the inhibition of a task that concurrently affords an incongruent response, which is labelled dimension inhibition (Goschke, 2000). Using targets that afford three tasks, we demonstrated that this only occurs when a single alternative task affords an incongruent response, with the inhibition being specific to that task. The second type of inhibition that we observed was backwards inhibition—the suppression of a recently abandoned task-set (Mayr & Keele, 2000). Unlike dimension inhibition, backwards inhibition was not triggered by the response incongruence of the unperformed tasks, or even whether the target afforded responses via the unperformed tasks. These two purported types of inhibition did not co-occur, and neither did the factors of response congruence and whether that task was recently abandoned interact. We therefore suggest that task-specific inhibition can be applied/triggered differently depending upon the paradigm, perhaps depending upon the extent to which alternative tasks, and therefore potentially other responses, are triggered by the target.

Keywords:

• Task switching
• Backwards inhibition
• Task-set control

Notes

¹ Backwards inhibition is conceptually similar to “inhibition of return” (IOR). IOR refers to participants' bias against returning their spatial attention to a previously attended location (Milliken, Tipper, Houghton, & Lupianez, 2000; Posner & Cohen, 1984). Backwards inhibition is essentially IOR at the level of a task-set.

² Conceptually, dimension inhibition shares some characteristics with negative priming. For instance, in spatial negative priming participants are slower to respond to targets that appear in locations previously occupied by distractors (e.g., Tipper, Brehaut, & Driver, 1990). Negative priming can also occur at an object level, with participants being slower to respond to a target if that target object previously appeared as a distractor (e.g., Tipper, 1985). Dimension inhibition is essentially a specific type of negative priming at a task-set level: Participants are slower to use a task-set if that task-set previously afforded an incongruent response and was thus previously distracting.