May, KA; Zhaoping, L; (2009) Effects of surrounding frame on visual search for vertical or tilted bars. Journal of vision , 9 (13) , Article 20. 10.1167/9.13.20.
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It is easier to find a tilted bar among vertical bars than vice-versa, but this asymmetry can be abolished or reversed by surrounding the bars with a tilted frame. The frame effect is important because it challenges bottom-up models of saliency. We conducted two experiments to investigate the causes of this effect. In Experiment 1, we removed different components of a square frame, and concluded that the frame effect was caused by a combination of (1) high-level configural cues that provided a frame of reference, and (2) bottom-up iso-orientation competition from the sides of the frame parallel to the bars. The iso-orientation competition could have arisen from (1) diversion of attention to the parts of the frame parallel to the target, or (2) iso-orientation suppression between nearby units selective for the same orientation. Experiment 2 investigated the nature of the iso-orientation competition process. In this experiment, we used a single line (the "axis") embedded in a circular field of bar elements, rather than a square frame surrounding them. The effect of the axis declined rapidly to zero with increasing target-axis distance, suggesting that the iso-orientation competition was caused entirely by iso-orientation suppression between nearby units tuned to the same orientation.
|Title:||Effects of surrounding frame on visual search for vertical or tilted bars|
|Open access status:||An open access version is available from UCL Discovery|
|Keywords:||Visual search, Orientation, Top-down, Bottom-up, Iso-orientation suppression, Cat striate cortex, Simple receptive-fields, Line-target detection, Early vision, Contextual influences, Orientation contrast, Stimulus orientation, Feature-integration, Spatial-frequency, Natural images|
|UCL classification:||UCL > School of BEAMS > Faculty of Engineering Science > Computer Science|
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