Priming of pop-out: I. Role of features

We examined a visual search task, in which observers responded to the high-acuityaspect of a pop-out target (shape of an odd-colored diamond or vernier offset of an odd spatial-frequency patch). Repetition of the attention-driving feature (color or spatial frequency) in this task primes the pop-out; repetition of the high-acuity aspect (shape, vernier offset) does not. Priming of pop-out is due to a decaying memory trace of the attention-focusing feature laid down with each trial. The trace ex-erts a diminishing effect over the following five to eight trials (-30 sec), and its influence over this time is cumulative. Observers cannot willfully overcome the priming, which suggests that it is pas-sive and autonomous. Both target facilitation and distractor inhibition are evident; the former has a greater effect. The phenomenon shows complete binocular transfer. In a typical visual search experiment, the observer's task is to detect the presence of the odd target within a field of distractors. Two well-known effects have been observed. Serial search is the term attributed to the find-ing that an increasing number ofdistractors increases the time necessary to find the target, yielding positive slop