The action effect: Support for the biased competition hypothesis.

The action effect refers to the finding that faster response times are found when a previously responded to stimulus contains a target item than when it serves as a distracting item in a visual search. The action effect has proven robust to a number of perceptual and attentional manipulations, but the mechanisms underlying it remain unclear. In the current study, we present two experiments investigating a possible underlying mechanism of the action effect; that responding to a stimulus increases its attentional weight causing the system to prioritize it in the visual search. In Experiment 1, we presented the search stimulus in isolation and found no evidence of an action effect. Thus, when there was no requirement for prioritization, there was no action effect. In Experiment 2, we tested whether stimulus-based priming (rather than the action) can account for the observed validity effects. We found no evidence of a priming effect when there were never any actions. These findings are consistent with the biased competition hypothesis and provide a framework for explaining the action effect while also ruling out other potential explanations such as event file updating.