Abstract
Humans are known to employ different attentional control settings flexibly in complex environment, dependent on the nature of the task. However, little is known about how observers adapt their attention to changes in a non-target dimension when this dimension is shape. In two experiments (online and lab versions, respectively), we investigated how observers adapt their target choices while searching for color singletons among distractors that dynamically changed their shape ratio. Two colored targets differed in shape but share the shapes with two sets of distractors. Participants were free to choose whichever target they preferred. The results showed that participants adapted their choices to the distractor shape ratio: even though the task could be solved by considering color alone, participants tended to select the target from the smaller shape set, and switched preferences as the shape ratio varied. We concluded that participants adapted their behavior to slight changes in the environment by statistical learning. A Bayesian modeling approach quantified the degree and speed of adaptation, revealing that the shape dimension (similar to color context in earlier studies) affects people's attentional control settings in dynamically varying contexts.