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Jing Samantha Pan, Rachel Coats, Geoffrey Bingham; Metric visual information about distance entails informational units. Journal of Vision 2011;11(11):972. doi: 10.1167/11.11.972.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: Mon-Williams and Bingham (2007) showed that perception must be calibrated to yield accurate targeted actions and argued that metric units of visual information about target distance are mapped to the unit of the targeted action. The implications of this mapping have not been systematically described and investigated. If it is the size of the units that is calibrated, then subsequent change of the units should alter the slope of a relation between actual and perceived distance as revealed by targeted actions. Methods: Sixteen participants performed an open loop action, moving an unseen marker using a rope and pulleys to visible targets (placed between 50 and 250 cm from the participant) in the dark. In Experiment 1, participants binocularly viewed a point light at eye level and the binocular unit, inter-pupillary distance (IPD), was altered by 1.6 cm. In Experiment 2, participants monocularly viewed phosphorescent targets on a phosphorescent textured surface with the monocular unit, eye height (EH), at 24 cm or 48 cm. Participants were calibrated to a certain IPD/EH, and then tested with altered IPD/EH. Performance before and after unit change was compared. Results: Linear fit of responses to target distances yielded significant slope change (p < 0.02) with changing EH and IPD units. When participants were tested with larger IPD after calibrating to smaller IPD, the slope was 0.93; conversely, when tested with smaller IPD after calibrating to larger IPD, the slope was 1.19. When participants were tested with large EH after calibrating to small EH, the slope was 1.04 and when tested with small EH after calibrating to large EH, the slope was 1.39. Responses using consistently large or small calibrated units were not different in either monocular-EH or binocular-IPD case. The results confirmed that perception of metric distance in depth is specified by sources of information that entail metric units.
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