Abstract

We measured reaction times (RTs) as observers searched for a target among a variable number of distractors. In searches for stimuli defined by conjunction of color and form (e.g., target: green +, distractors: red +, green ×), Treisman found that RTs increase as the number of distractors increase. Observers appear to conduct serial self-terminating searches for the target. We replicated this finding with naive observers. However, after 1000 trials of practice, RTs for two observers were independent of the number of distractors indicating that they could perform parallel searches for conjunctions. Egeth ef al¹ argue that observers can simultaneously disregard all distractors along one dimension (e.g., color). Therefore, we used a triple conjunction task of form, color, and size. (Target: large green +; distractors: large green ×, large red +, small green +, small red ×.) The stimuli were chosen so that if an observer was able to disregard all the distractors of one color, the remaining stimuli would still require search for a conjunction.

© 1987 Optical Society of America