Abstract
Salient items usually capture attention, thus are beneficial to visual search. Our previous work, nevertheless, discovered that a collinear salient column can impair local visual search (Jingling & Tseng, 2012). Our display contains horizontal (or vertical) bars regularly arranged in 21 rows and 27 columns, while one column was filled with orthogonal bars, making this column uniquely salient in the display grouped either in collinear or in non-collinear. Observers’ task was to discriminate an oriented black bar locating either on the salient column or on the background. Interestingly, responses were slower for a target overlapping on the salient column than on background if the salient column was collinear, while shorter if non-collinear. The goal of this study is to investigate whether the impairment only occurs when a task-irrelevant column is uniquely salient in a search display. This question is important for understanding how contour integration interacts with salience computation, an area that was little studied. In Experiment 1, we reduced the column salience by replacing the homogeneous search display with alternating collinear/non-collinear columns. Observers still needed longer time to discriminate target orientation when the target overlapped with collinear column than non-collinear column. In Experiment 2, we divided the search display into two regions: collinear and non-collinear columns. The salience was the highest at the regions’ border, and less at non-border columns. Observers performed the same search, and their RTs were highest when targets on collinear border bars, then on collinear non-border bars, followed by on non-collinear non-border bars, and shortest on non-collinear border bars. This result suggests that collinear contour per se delays local target search, while its spatial uniqueness and boarder location could further slow down target search. This observation is consistent with the neuronal properties in V1, which we speculated a possible site for this interaction.
Meeting abstract presented at VSS 2013