Detecting contour targets amongst temporally segmented and non-segmented distractors

Abstract

We report two experiments where participants were required to make a four alternative forced choice judgement concerning the location of a contour target formed from spatially separate line elements set amongst a background of randomly oriented line elements. In both experiments, target contours were presented temporally segmented (out-of-phase) and non-segmented (in phase; at 72 Hz) from distractors with displays being presented for 133 ms. In Experiment 1 the degree of curvature was varied with contour having 10, 20 or 40 degrees of curvature. The results showed that contour detection decreased as curvature increased but that there was always an advantage in the temporally segmented over non-segmented conditions (unless performance was at chance). The advantage of temporally segmented over non-segmented conditions was found whether contours preceded distractors or distractors preceded contours. In Experiment 2, the temporal segmentation of contours and distractors was restricted to the first two stimulus frames and was followed by temporally non-segmented presentation of all other frames. The effect of this manipulation was to reduce but not eliminate the advantage for temporally segmented over non-segmented presentations suggesting the advantage for segmented displays accumulated across time. Potential explanations for better performance in temporally segmented over non-segmented conditions will be discussed.