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Barbara Gillam; Large individual differences in the weighting of perspective and stereoscopic information in slant perception; implications for cue combination approaches. . Journal of Vision 2016;16(12):650. doi: https://doi.org/10.1167/16.12.650.
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© ARVO (1962-2015); The Authors (2016-present)
Previously unpublished individual data are presented for 12 participants in a cue conflict experiment (Gillam 1967). Stimuli were three frontal plane perspective patterns of dotted lines. Visual angle extents were 15 deg (H) and 9 deg (V). Distance was 56 cm. One pattern had equally-spaced vertical lines, one equally-spaced horizontal lines and the other a combination (grid). Stereoscopic slants around a vertical axis ranging from 4 to 33 deg. were imposed by uniocular horizontal magnification using aniseikonic lenses, creating conflict with the frontal plane perspective. A monocular comparator, validated using full cue slants, recorded perceived slant. Participants were screened for stereoacuity (>30 arcsec.) Results and discussion. (a) Individual differences were reliable and large, ranging from stereopsis having all the weight to having only moderate weight. For 4 observers data were close to the predicted stereo response function regardless of pattern. For the observers who showed an effect of conflicting perspective, horizontal lines (linear perspective) reduced perceived slant much more than vertical lines (foreshortening) with an intermediate effect for the grid. (b) Four observers showed this pattern of attenuation across stereo slants, while four only at greater stereo slants. Thus contrary to other studies, increasing conflict tended to reduce rather than increase the influence of stereo. (c) The fact that the two components of perspective compression, foreshortening and linear perspective, received very different weights, suggests that reported weightings in the literature of broadly-defined "cues" such as "texture" may lack generality. (d) Adding the two components of perspective via the grid pattern did not increase the weight given to perspective but the weight given to stereopsis. Even though the dotted lines all provided ample potential stereo information, configuration influenced stereo dominance. Thus stereo should not be regarded as a modular slant cue.
Meeting abstract presented at VSS 2016
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