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Naomi M. Kenner, Aude Oliva; Rapid goal-directed exploration of a scene: The choice between a direct and a pragmatic scan path. Journal of Vision 2005;5(8):438. doi: 10.1167/5.8.438.
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When searching for a target at a cued location in a limited amount of time, an obvious search strategy is to direct your first saccade to that location. Even when the probability of the target being at that location drops between 100% and 50%, sending your eyes there before you look elsewhere still sounds like a good idea. Araujo, Kowler, and Pavel (2001, Vis. Res.) found that, counterintuitively, most participants (Ps) routinely made initial saccades to low-probability locations despite a resulting accuracy cost. Why would this indirect scan path be a good idea at all? When information about target location is given prior to a brief (∼500 ms) presentation of the search display, Ps can set attentional weights for each spatial location and plan saccades accordingly. If a two-saccade path is anticipated, it may actually be cheaper in terms of planning and enacting saccades to look from the low- to the high-probability location: the eyes would be more automatically drawn to the high probability location from the low probability side than in the converse situation. The present experiments explore the conditions under which the indirect (Pragmatic) path is chosen over the Direct path. Ps viewed 2 clusters of items for a brief time (250, 500 ms) and reported if the target was normal or reversed. Their eye movements were recorded with an ISCAN eyetracker. Before each trial Ps were told target identity, the locations of the 2 clusters, and each cluster's probability of containing the target (Definite, Equal, or Weighted). We varied the complexity of items (digital numbers, objects) and background (blank, indoor scene). Under these conditions, contrary to those used by Araujo et al., very few Ps used the Pragmatic path and error rates were low. Further variations of display complexity and task constraints will be presented to examine the modulation of the choice between a Direct and a Pragmatic scan path in the rapid goal-directed exploration of a visual scene.
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