After-search--visual search by gaze shifts after input image vanishes.
It has been known that if an image containing many random items suddenly disappears, visual persistence and iconic memory vanish within approximately 0.2 seconds, such that observers are unable to report the identities of the items not graced by attention. We show that effects of the salience of image items can remain for up to more than a second longer, influencing both eye movements and explicit choice. In our experiment, subjects searched for a moderately salient target among 659 non-targets to report whether the target was in the left or right half of the display, guessing if necessary, while their gaze was tracked. In some trials, the search display was replaced by a mask before their gaze reached the target. We call such trials 'after-search' trials, and the behavior after the mask onset is after-searching. In after-search, subjects made 3.1 +/- 2.8 saccades on the mask before reporting. In some after-search trials called 'gaze-arrival' trials, they looked at the location of the vanished target after up to several on-mask saccades; in these trials, the subjects' reports were more accurate. This saliency effect begs the question of what memory, saccade generation, or other neural mechanisms might be responsible.
Zhaoping
Li
L
Department of Computer Science, University College London, UK. z.li@ucl.ac.uk
D000293:Adolescent; D000328:Adult; D005403:Fixation, Ocular / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010470:Perceptual Masking; D010775:Photic Stimulation / Q000379:methods*; D012438:Saccades / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*; D055815:Young Adult