Purpose: In visual search, the abrupt onset of a new object draws attention regardless of the observer's goals, but other salient features (e.g. color singletons) do not. Abrupt onsets may capture because they signal the appearance of a new object or because they are simply unusual and anomalous. If abrupt onsets capture because they signal a new object, then new objects appearing via disocclusion (which is not anomalous) should also capture. If abrupt onsets capture because they are anomalous, then disoccluding objects should not capture. If both of these stimuli capture because they signal a behaviorally important event, then a looming, but not new, object might also capture, because it signals an important event. Methods: We tested abrupt onsets, disocclusions, moving objects (same motion as disoccluding object but without appearing late), looming objects (increasing in size), and receding objects (decreasing in size) in the irrelevant feature paradigm (e.g. Yantis & Hillstrom, 1994). Abruptly onsetting letters appear as other letters are unmasked. Disoccluding, moving, looming, or receding letters are unmasked when the motion is completed. Observers searched for one of two target letters among letter distractors. The unique feature was unpredictive of the target location. Results: When the target happened to be the item that onset, disoccluded, or loomed, search slopes were significantly smaller, indicating that these events draw attention even though their uniqueness was irrelevant to the search task. Slopes were not reduced when the target was a unique moving or receding item. Conclusions: The visual system may automatically give priority to new objects and to other potentially behaviorally important stimuli.
ASJC Scopus subject areas