The mind's average: Unseen, internally generated ensemble representations can guide visual attention.

Ensemble processing, which allows the visual system to form summary statistical representations (e.g., the average size of a bowl of apples), can be influenced by attention. However, can such internally, statistically generated representations influence the deployment of attention? To answer this question, we conducted two experiments using a modified version of an attentional cueing paradigm with an ensemble task. Each trial began by displaying an array of eight ovals of varying sizes. Next, two ovals to the left and right of fixation were presented, where one oval was the average size of the previous set (the ensemble object), and the other oval was a distractor (the foil object). On different trials, participants reported either which oval corresponded to the average size of the previous set (ensemble task) or the location of a probe dot on one of the objects (probe task). Experiment 1 used 80% ensemble task trials and further examined effects of attentional deployment when the foil object was outside the range of ensemble size values compared to inside the ensemble range. The results revealed attentional guidance when the foil was outside the ensemble range. Experiment 2 used 20% ensemble task trials with foils outside the ensemble range and found no attentional guidance, revealing that the strength of the internal ensemble representation affects whether or not attentional guidance effects will be observed. Overall, the results provide evidence that ensemble representations can influence the deployment of spatial attention, thereby demonstrating that these two cognitive mechanisms reciprocally interact.