UCL logo

UCL Discovery

UCL home » Library Services » Electronic resources » UCL Discovery

A Clash of Bottom-Up and Top-Down Processes in Visual Search: The Reversed Letter Effect Revisited

Zhaoping, L; Frith, U; (2011) A Clash of Bottom-Up and Top-Down Processes in Visual Search: The Reversed Letter Effect Revisited. J EXP PSYCHOL HUMAN , 37 (4) 997 - 1006. 10.1037/a0023099.

Full text not available from this repository.

Abstract

It is harder to find the letter "N" among its mirror reversals than vice versa, an inconvenient finding for bottom-up saliency accounts based on primary visual cortex (V1) mechanisms. However, in line with this account, we found that in dense search arrays, gaze first landed on either target equally fast. Remarkably, after first landing, gaze often strayed away again and target report was delayed. This delay was longer for target "N" We suggest that the delay arose because bottom-up saliency clashed with top-down shape recognition. Thus, although gaze landed accurately and quickly to the distinctive feature in the target shape (the orientation of the diagonal bar in "N" or "(sic)"), the identical zigzag shape of target and distractors was registered, leading to temporary confusion. In sparser search arrays with smaller set sizes, top-down target shape recognition occurs earlier and bottom-up saliency is weaker. The clash in this case causes search asymmetry even before target location at first gaze landing. Our findings rule out previous suggestions that search asymmetry stems from stronger preattentive salience for the reversed target and/or faster rejection of familiar distractors.

Type:Article
Title:A Clash of Bottom-Up and Top-Down Processes in Visual Search: The Reversed Letter Effect Revisited
DOI:10.1037/a0023099
Keywords:visual search, saliency, familiarity, object recognition, CONTEXTUAL INFLUENCES, OBJECT RECOGNITION, SALIENCY MAP, POP-OUT, CORTEX, FAMILIARITY, ASYMMETRY, ATTENTION, SEGMENTATION, INTERFERENCE
UCL classification:UCL > School of Life and Medical Sciences > Faculty of Brain Sciences > Psychology and Language Sciences (Division of) > Institute of Cognitive Neuroscience
UCL > School of BEAMS > Faculty of Engineering Science > Computer Science

Archive Staff Only: edit this record