Conducted an RT experiment with 33 male and 39 female 18-39 yr. olds. An effect of stimulus set size was found with a paradigm in which all stimuli were mapped onto a single response. The effect was essentially unchanged when the stimuli (letters) were inverted or when each stimulus was also associated with a unique foveal location. The effect was transient. Results suggest a switch in processing strategy from a focal attentive to a preattentive mode. (23 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)