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ISSN : 1226-9654

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Vol.20 No.4

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Asymmetric Effects of Cast Shadow Directions on Visual Search

The Korean Journal of Cognitive and Biological Psychology / The Korean Journal of Cognitive and Biological Psychology, (P)1226-9654; (E)2733-466X
2008, v.20 no.4, pp.265-283
https://doi.org/10.22172/cogbio.2008.20.4.004


& (2008). Asymmetric Effects of Cast Shadow Directions on Visual Search. The Korean Journal of Cognitive and Biological Psychology, 20(4), 265-283, https://doi.org/10.22172/cogbio.2008.20.4.004

Abstract

In this study, the effects of cast shadow directions on visual search were investigated. Rensink and Cavanagh(2004) reported that search based on cast shadow can have a significant influence on the speed of visual search. Here we manipulated directions of cast shadow and arrangement positions, to test whether there is a preferred direction of illumination in the processing of cast shadow. Target and distracters had identical cast shadow directions, and target differed from distracters only in the orientation of cast shadow. In Experiment 1, two-dimensional shapes were used consisting of vertically oriented rectangles and quadrilateral, and in Experiment 2, three-dimensional cylinders were adopted. Results show that search was consistently slower for the normal ground arrangement than for the ceiling arrangement across the conditions. In addition, cast shadow directions had asymmetric effects on search time, depending on the object types. When the stimuli were arranged on the ground, search for the left-lit condition tended to be slower than for the right-lit condition in Experiment 1, whereas search for the left-lit condition tended to be faster than for the right-lit condition in Experiment 2. These findings imply that the processing of right-side cast shadow seems to be more influenced by objects' 2- or 3-dimensional property than that of left-side one. It is suggested possible differential processing related with the fact that human perceives as more familiar scene left-lit world where the shadow is cast on right-side.

keywords
visual search, cast shadow, illumination, 3-D object perception, 시각 탐색, 그림자, 조명방향

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