Does ocular origin of stimuli always help you find a target? It depends!

Abstract

Salience maps guide attentional deployment. Ocular origin of stimuli has recently been discovered to contribute to salience computation in addition to orientation, luminance and color (Zhaoping, 2008). However, how it interplays with other simple features is little understood. We investigated how ocular origin of stimuli interacts with color and luminance in a visual search task. The search display contained 9 × 9 vertical green bars against a black background (Experiment 1) or dark-grey bars against a mid-grey background (Experiment 2). One randomly selected singleton column was colored red (Experiment 1) or light grey (Experiment 2) in five possible locations. Another column, independently selected, was presented to a different eye (ocular singleton) from the other columns. Observers reported the orientation of a target, a small tilted gap on one of the bars. We found in Experiment 1 that targets congruent with the ocular singleton were slower to be detected than those incongruent with the ocular singleton, but there was no effect on the color-defined singleton. Interestingly, in Experiment 2, we found no effect of ocular origin but the search facilitation for targets overlapped with the luminance singleton. Our findings that the ocular origin of stimuli works distinctly with color and luminance here imply these features are interactively coded during salience computation for visual search.