The time course of attention is a major characteristic on which different types of attention diverge. In addition to explicit goals and salient stimuli, spatial attention is influenced by past experience. In contextual cueing, behaviorally relevant stimuli are more quickly found when they appear in a spatial context that has previously been encountered than when they appear in a new context. In this study, we investigated the time that it takes for contextual cueing to develop following the onset of search layout cues. In three experiments, participants searched for a T target in an array of Ls. Each array was consistently associated with a single target location. In a testing phase, we manipulated the stimulus onset asynchrony (SOA) between the repeated spatial layout and the search display. Contextual cueing was equivalent for a wide range of SOAs between 0 and 1,000 ms. The lack of an increase in contextual cueing with increasing cue durations suggests that as an implicit learning mechanism, contextual cueing cannot be effectively used until search begins.Keywords Spatial attention . Contextual cueing . Visual search . Implicit learningThe modern world presents us with a myriad of sensory inputs, only a subset of which are behaviorally relevant. Selective attention depends partially on one's previous experience. For example, in studies on contextual cueing, participants become faster searching for a target on displays that occasionally repeat (Chun & Jiang, 1998). Several neurophysiological studies have investigated the time course of contextual cueing, demonstrating relatively rapid emergence of the cueing effect. However, these findings have not been corroborated in behavioral work. The goal of the present study was to characterize the time course of contextual cueing in behavior.In an intracranial electroencephalography (EEG) study, Olson, Chun, and Allison (2001) observed a significantly greater N210 wave (in V1/V2) approximately 200 ms after viewing of a previously encountered display rather than a new display. Similarly, scalp event-related potential (ERP) studies have reported a significantly greater N2pc component for repeated than for unrepeated displays approximately 200 ms after display onset (Johnson, Woodman, Braun, & Luck, 2007;Schankin & Schubö, 2009). Because N2pc is an index of spatial attention (Luck & Hillyard, 1994), these differences suggest that contextual cueing affects spatial attention relatively early. Earlier time differences were observed with magnetoencephalography (MEG). In one MEG study, participants were presented with repeated search layouts, some with consistent and others with random target locations. After search onset, greater gamma activity occurred 100-300 ms earlier in the consistent than in the random condition (Chaumon, Drouet, & Tallon-Baudry, 2008). Predictable search layouts appear to affect brain activity shortly after search onset.Does the early time course that has been observed with ERPs and MEG translate into an early behavioral gain? This question ha...