You see what you look for: perceptual biases induced by targets and distractors in visual search

Visual perception is, at any given moment, strongly influenced by its temporal context – what stimuli have recently been perceived and in what surroundings. We have previously shown that to-be-ignored items produce a bias upon subsequent perception that acts in parallel with other biases induced by attended items. However, our previous investigations were confined to biases upon a visual search target's perceived orientation, and it is unclear whether these biases influence perception in a more general sense. Canonical paradigms investigating so-called serial dependence have revealed biases in the perception of items not associated with any particular task. Therefore, we test here whether the biases from visual search targets and distractors affect the perceived orientation of a neutral test line, which is neither a target nor a distractor. To do so, we asked participants to search for an oddly oriented line among distractors and report its location for a few trials and then presented a task-irrelevant test line. Next, participants were asked to report the orientation of the test line. Our results indicate that in tasks involving visual search, targets induce a positive bias upon a neutral test line if their orientations are similar, and distractors also produce a repulsive bias if the test line's orientations and the distractors' average orientation are far apart in feature space. Additionally, our results show that proximity in feature space between previous and current stimuli plays a large role in determining the direction of the perceptual biases.