DOI: 10.6129/CJP.20141217
Chinese Journal of Psychology 2015, Vol.57, No. 1, 91-107

Temporal Characteristics of the Collinear Masking Effect in Visual Search

Ching-Wen Chiu（Graduate Institute of Neural and Cognitive Sciences, China Medical University）；Li Jingling（Graduate Institute of Neural and Cognitive Sciences, China Medical University）

Abstract

A salient target is usually easier to find in visual search. However, perceptual grouping, collinearity in particular,
can reverse this observation. The phenomenon, called the collinear masking effect, was observed for a search display that was filled with horizontal bars while a column of bars were vertical (the collinear column). This collinear column thus is salient and well-grouped. The task was to discriminate a small oriented bar either in the collinear column or in other columns in the background. The collinear masking effect refers to the phenomenon that discrimination was slower for a target on the collinear column comparing to that in the background. Since feature saliency affect visual search in relatively early (e.g., 40 to 70 ms) while feature conjunctions late (e.g., 150 to 300 ms) in information process stages, we examined the time course of the collinear masking effect in this study. With limited presentation durations (40, 70, 150, or 300 ms), different masks lead to different results. Nevertheless, the collinear masking effect was observed at the time point when the target discrimination was above chance level. Further experiment showed that if the search display was presented preceded the target, reliable collinear masking effect was obtained as early as 40 ms. We thus concluded that the collinear masking effect can be found in 40 to 70 ms. Our results imply that the collinear masking effect occurred as fast as saliency was calculated, suggesting that collinear grouping interferes with visual search very early in the
information processing stream.

Keywords: attention, perceptual grouping, visual search, time course, masking