Color differences required for parallel visual search

Abstract

In previous experiments we have found that the time required to find a target disk among equalluminance distractors depended on the chromaticity difference between target and distractors. When the chromaticity difference was a small search time increased with the number of distractor items in the display indicating a serial search. When the chromaticity difference was large, the search time was approximately constant regardless of the number of distractors in the display indicating a parallel search. In the experiments to be described here we examined the effects of luminance differences on search times. Search times were measured as a function of luminance difference and number of distractors for targets and distractors of the same chromaticity. When the luminance difference was small, the search time increased with the number of distractors indicating a serial search. When the luminance difference was large, search times were approximately constant suggesting parallel search. Results for targets that differ from distractors in both chromaticity and luminance are also discussed. The chromaticity and luminance differences required for parallel search are many times threshold. The parallel search as a criterion for defining large color differences is discussed.