Familiarity and pop-out in visual search.

In this paper, we report that when the low-level features of targets and distractors are held constant, visual search performance can be strongly influenced by familiarity. In the first condition, a [symbol: see text] was the target amid [symbol: see text]s as distractors, and vice versa. The response time increased steeply as a function of number of distractors (82 msec/item). When the same stimuli were rotated by 90 degrees (the second condition), however, they became familiar patterns--2 and 5--and gave rise to much shallower search functions (31 msec/item). In the third condition, when the search was for a familiar target, N (or Z), among unfamiliar distractors, [symbol: see text]s (or [symbol: see text]s), the slope was about 46 msec/item. In the last condition, when the search was for an unfamiliar target, [symbol: see text] (or [symbol: see text]), among familiar distractors, Ns (or Zs), parallel search functions were found with a slope of about 1.5 msec/item. These results show that familiarity speeds visual search and that it does so principally when the distractors, not the targets, are familiar.