Odd-men-out are poorly localized in brief exposures

Signal detection theory (SDT) asserts that sensory analysis is limited only by noise, and not by the number of stimuli analysed. To test this claim, we measured the accuracy of visual search for a single tilted element (the target) among 7 horizontal elements (distractors) using several different exposure durations, each terminated by a random noise mask. In the uncued condition, each element was a potential target. In the cued condition only 2 were. SDT predicts that location errors should be evenly distributed among all distractors. For long exposures (eg, 5.0 seconds), this prediction was confirmed, and SDT could simultaneously fit uncued and cued accuracies. For short exposures (eg, 0.1 seconds), errors were concentrated among distractors adjacent to the target, and, unless modified to account for this, SDT underestimated the difference between uncued and cued accuracies. Therefore, when the time available for search is brief, odd-men-out (ie, featural discontinuities) can be seen, but their positions can be only roughly estimated.