Statistical learning shapes distractor suppression

Even though traditionally attentional control is considered to be the result of the interaction between top-down and bottom-up mechanisms, Awh, Belopolsky and Theeuwes (2012, TICS) have suggested a theoretical framework in which this division is argued to be incomplete. They argued that the history of attentional deployments can elicit lingering selection biases, which are unrelated to top-down goals or the physical salience of items. Whereas previous work has primarily focused on target selection, here we investigated whether implicitly learned statistical regularities can influence distractor processing. We used the additional singleton task in which participants search for a salient shape singleton while ignoring a color distractor singleton. This color distractor was systematically presented more often in one location than in all other locations. Using measures of behavior, we demonstrate that for this high-probability location, both the amount of attentional capture by distractors and the efficiency of selecting the target were reduced. Measures of brain activity, specifically the Pd (distractor positivity) and N2pc components of the event-related potential, were used to track the allocation of attention and suppression to lateralized positions in the arrays. We find evidence for a Pd-like component for the high probability location, even though both the target and the distractor were presented on the vertical meridian (top and bottom) and thus could not themselves elicit a lateralized component in the ERP. When the distractor was presented at the lateralized high probability location, this also generated a Pd, while a distractor presented at a low probability location generated an N2pc. The same was found for when the target was presented at the high versus low lateralized probability location. We interpret these findings as evidence that spatial statistical regularities influence distractor processing through inhibition of high probability locations.