Academic journal article Perception and Psychophysics

In Sight, out of Mind: The Role of Eye Movements in the Rapid Resumption of Visual Search

Academic journal article Perception and Psychophysics

In Sight, out of Mind: The Role of Eye Movements in the Rapid Resumption of Visual Search

Article excerpt

Three experiments investigated the role of eye movements in the rapid resumption of an interrupted search. Passive monitoring of eye position in Experiment 1 showed that rapid resumption was associated with a short distance between the eye and the target on the next-to-last look before target detection. Experiments 2 and 3 used two different methods for presenting the target to the point of eye fixation on some trials. If eye position alone is predictive, rapid resumption should increase when the target is near fixation. The results showed that gaze-contingent targets increased overall search success, but that the proportion of rapid responses decreased dramatically. We conclude that rather than depending on a high-quality single look at a search target, rapid resumption of search depends on two glances; a first glance in which a hypothesis is formed, and a second glance in which the hypothesis is confirmed.

Imagine you are looking for your favorite can of soup in the supermarket and, before you find it, someone walks in front of you, momentarily blocking your view. Based on the results of a recent study, you will likely benefit from even a 100-msec glance at the shelves when you resume looking for your soup after the interruption. Specifically, Lleras, Rensink, and Enns (2005) found that humans resume an interrupted search much more quickly than they are able to begin a new search.

Lleras et al. (200S) presented participants with a modified search task in which participants were presented with only brief glimpses of the search display ("look" times were typically around 100 msec). Observers were required to report the color of a target rotated T shape presented among rotated L shapes. The presentation of the search display was followed by blank screens of longer durations of around 900 msec. Search and blank displays were alternatively presented until the observer responded to the identity of the target. The results showed that in 75% of all trials, participants were able to correctly identify the target within three presentations of the search display. Moreover, the results showed that successful responses to the second and subsequent search displays occurred much earlier in time than the responses elicited following the first initial search display. Following second and subsequent displays, participants often showed extremely short response latencies to target identification (below 400 msec.), a finding Lleras et al. (2005) referred to as rapid resumption.

It was argued that the ability of observers to rapidly resume an interrupted search is the result of target relevant preprocessing of the display in earlier looks (Lleras et al., 2005). In brief, based on the available information in first presentation of the search display, observers form a perceptual hypothesis regarding the relevant target features. The results are consistent with the perceptual hypothesis including information specific to the response required of the target (i.e., only task-relevant target features are represented) (Lleras, Rensink, & Enns, 2007). In order to confirm the hypothesis, one additional look is required to match the perceptual hypothesis with incoming sensory information. Rapid resumption occurs because a hypothesis based on a previous glance can be tested very rapidly in a subsequent glance, given that the initial hypothesisgeneration step has already been performed. The finding that people are able to rapidly resume search points to an important role for memory in visual search (Lleras et al., 2005,2007).

However, there is an alternative explanation that does not appeal to any memory processes. Perhaps the rapid resumption effect is an artifact of simply finding a target close to where the eye is currently fixated, with the high spatial and color resolution of the fovea permitting target identification in less time than when the target appears more eccentrically. If so, then rapid resumption should be more likely when the eyes are near the target in a search display, rather than reflecting any memorial process. …

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