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John W. Philbeck, Shannon O'Leary, Audra Lyn Blohm Lew; Path integration precision is doubled by the imagined proximity of previewed landmarks. Journal of Vision 2003;3(9):133. doi: 10.1167/3.9.133.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: When navigating with vision, humans can determine their location by visually perceiving their distance and bearing relative to a landmark at a known location. When navigating without vision, positional uncertainty tends to increase with walked distance; if one believes a landmark is very nearby, however, one might disregard any uncertainty accumulated up to that point. If this happens, it should increase response precision in path integration tasks. This study tested that prediction.
Method: Part 1: 36 participants binocularly viewed a single target cone at 2, 4.2, or 6.2 m in a well-lit room and attempted to walk to it without vision (5 repetitions per target). Part 2: using the same method, 12 participants walked 5 times to a previewed target at 6.2 m; 24 others saw a “landmark” cone on the path at 4.2 m in addition to the 6.2 m target. 12 of these participants received auditory feedback about the landmark's location as they passed (via pulsed noise bursts), while the rest saw both the landmark and target cones but received no feedback while passing the landmark. All participants wore hearing protectors to minimize uncontrolled auditory cues.
Results: Response precision in Part 1, as measured by within-subject standard deviations (SD's), averaged 9.2% of the target distance for all 3 groups. Precision for the no-landmark group was unchanged in Part 2, while SD's for the 2 landmark groups dropped by nearly half to 4.7% of the target distance and did not differ between these 2 groups. All groups overwalked slightly (averaging +15 and +36 cm in Parts 1 and 2, respectively), with no group differences.
Conclusions: When approaching the remembered location of a previewed landmark, blindfolded navigators behave as if their positional estimate has become more precise, even in the absence of environmental location cues. Apparently, remembered landmarks can reduce some of the positional uncertainty that accumulates when navigating by path integration.
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