Priming of popout: Evidence for implicit short-term memory of feature and position

We examined a visual search task in which observers respond to the high-acuity aspect of a popout target (shape of an odd-colored diamond, vernier offset of an odd spatial frequency patch). Repetition of the attention-driving feature (color, spatial frequency) in this task primes the popout; repetition of the high acuity shape/response aspect does not. Both target facilitation and distractor inhibition are evident, the former having a greater effect. This priming is due to a decaying memory trace of the attention-focusing feature laid down with each trial. The trace exerts a diminishing effect over the following 5-8 trials ({dollar}{lcub}sim{rcub}30{dollar} seconds) and its influence over this time is cumulative. The color priming shows complete binocular-transfer.; The repetition of the target position also primes subsequent trials. Facilitation occurs when the target position is repeated on two consecutive trials. Inhibition occurs when the target falls where a distractor used to be. Somewhat diminished facilitation and inhibition exist for positions adjacent to those of the target and distractors. This spatially characteristic memory trace exerts the strongest influence on the most immediately succeeding trials and then it decays over approximately 8 trials. The target position facilitation is always stronger than the distractor position inhibition. Position priming is largely object centered.; We consider this priming of attentional deployment to be an example of implicit memory. Using a post-cued recall procedure embedded in the search task, we show that the explicit memory in this task has qualitatively different characteristics. First it is not selective as priming, but occurs for all three aspects of the previous trial: color, position and shape. Second, it is very short lasting, demonstrable over just one trial. Finally, observers cannot willfully overcome the priming, suggesting it is passive and autonomous.; We also examine the decay of the short term memory. We found no evidence for the passive decrement of memory over time with varied inter-trial intervals. Instead, the memory decayed over intervening different-color trials, thus suggesting that the act of focusing attention to odd-colored targets may be sufficient to lead to memory decay.