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Lindsey Shain, J. Farley Norman; Aging and the estimation of visual motion direction. Journal of Vision 2018;18(10):350. doi: 10.1167/18.10.350.
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© ARVO (1962-2015); The Authors (2016-present)
The perception of motion is subject to the aperture problem. When extended contours move behind occluding apertures, only the component of motion perpendicular to the orientation of the contour can be detected. The direction of contour motion is thus ambiguous. The visual system can solve the aperture problem and recover the true direction of object motion by integrating across multiple ambiguous motion signals. The stimulus displays were essentially identical to those of Mingolla, Todd, & Norman (1992). Rectangular arrays of 64 and 9 apertures were presented to 20 younger and older observers (mean ages were 22.1 and 74.3 years); each aperture contained a randomly-oriented line segment. The entire array of line segments moved together behind the apertures in one of 12 possible directions (zero to 330 degrees relative to vertical). Once each line segment reached its aperture's edge, it was recycled back to the opposite side; each line segment thus never left its respective aperture. The stimulus duration for each of the 120 trials per observer (2 aperture conditions x 12 directions of pattern motion x 5 repetitions) was 2.4 sec. The observers were required to estimate the exact direction of pattern motion (over the range of zero to 360 degrees) by adjusting the orientation of a pointer that appeared after the termination of each stimulus display. The results indicated that the younger observers' average error for estimating the direction of pattern motion was 9.4 and 26.2 degrees for the 64 and 9 aperture conditions, respectively. The errors of the older observers' direction judgments were higher: 22.0 degrees for the 64 motion signals/apertures condition and 35.0 degrees for the 9 motion signals/apertures condition. Despite some modest deterioration in accuracy, the current results demonstrate that older adults can effectively integrate locally ambiguous motion signals into a coherent perception of motion direction.
Meeting abstract presented at VSS 2018
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