Many daily tasks involve visual search, such as looking for a friend at the airport or snatching a drink from the fridge. Visual search is also a useful experimental paradigm for studying the nature of spatial attention (Treisman,
1988; Wolfe,
1994,
2007). Most studies in the lab present the search target at random locations on the display, but in the real world, the locations of search targets are often constrained by their context (Biederman,
1972; Biederman, Mezzanotte, & Rabinowitz,
1982). For example, a mailbox is often found on the side of the street rather than in the driveway. Laboratory studies have examined the impact of such statistical regularities on human performance. The general findings are that humans are highly sensitive to statistical regularities. For example, in contextual cuing, participants are faster to find a target within configurations that occasionally repeat (Brady & Chun,
2007; Chun & Jiang,
1998). In probability cuing, participants are faster to find a target in locations that frequently contained the target before (Geng & Behrmann,
2002,
2005; Jiang, Swallow, Rosenbaum, & Herzig,
2013; Miller,
1988). Statistical regularities modulate spatial attention. Contextual cuing increases the magnitude of
N2pc, a component of the event-related potential that indexes spatial attention (Johnson, Woodman, Braun, & Luck,
2007). Probability cuing results in reduced search slope—less time is needed per item when the target is in the high-probability locations (Jiang, Swallow, & Rosenbaum,
2013). Knowledge, including that acquired from implicit learning, serves as a powerful cue for spatial attention (Chun,
2000).