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Courtney Wallin, Daniel Gajewski, John Philbeck; Eye movement patterns during judgments of absolute distance in natural environments. Journal of Vision 2012;12(9):1003. doi: 10.1167/12.9.1003.
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© ARVO (1962-2015); The Authors (2016-present)
The nearby ground plane acts as a crucial reference frame for judging both near and far distances. However, it is unclear what role eye movements play in establishing this reference frame. Is the immediate ground plane preferentially fixated? What eye movement strategies do observers prefer? Do different response modes (i.e., action-based or not) elicit different gaze behaviors, and are some eye movement patterns associated with better performance? To address these questions, we monitored eye movements while participants viewed targets (2.75-5 m distant) for 3-5 seconds. In Experiment 1, observers used blindwalking or verbal report (between groups) to judge distances; eye movements were unconstrained. While the target was fixated at least once on 98% of the trials, the nearby ground plane was only fixated 50% of the time. When this region was fixated, viewing patterns varied greatly: the number of fixations per entry into the region ranged from 1 to 8, with some observers seemingly counting units between themselves and the object. Surprisingly, others adopted a steady gaze strategy (34% of trials), wherein the target, once fixated, was the only region fixated. Accuracy was equivalent between groups (mean error = -9%) and no differences in eye movement behaviors existed between response measures. Experiment 2 focused on the role of two particular eye movement strategies, with blindwalking as the response mode. Participants began each trial fixating the target; one group maintained a steady fixation on the object and the other was encouraged to scan around. Accuracy was equivalent between groups (mean error = -14%). In sum, results indicate that observers engage in a variety of gaze behaviors when judging absolute distances but these are not modulated by response mode. Furthermore, response accuracy is independent of viewing strategy, at least when multiple extended glimpses of the environment are available.
Meeting abstract presented at VSS 2012
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