Learning what to expect: context-specific control over intertrial priming effects in singleton search.

The present study explored the degree to which repetition effects in color pop-out search from trial n - 1 to trial n are subject to the attentional control settings of the observer. Intertrial priming effects were compared between two contexts that differed in terms of the utility of immediate prior experience for current performance; in one context, the target was likely to repeat, and in the other context, the target was likely to alternate from one trial to the next. Across two experiments, priming of pop-out (PoP) effects (Malkjovic & Nakayama; Memory & Cognition 22:657-672, 1994) were modulated in accord with the probability of target color repetition in a given trial context. Importantly, this modulation persisted when trial history preceding trial n - 1 was controlled for. Furthermore, this control over PoP seems not to derive from explicit strategies and is not an artifact of randomly occurring strings of same-target trials. We argue that priming effects in singleton search from trial n - 1 to trial n are subject to a form of implicit top-down control.