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Jeffrey D. Bower, Rui Ni, George J. Andersen; Aging and the detection of motion direction in random-dot stimuli. Journal of Vision 2005;5(8):663. doi: 10.1167/5.8.663.
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Age related decrements in detecting coherent motion are the result of a decreased ability to integrate direction information. Previous research has determined thresholds for determining the overall direction of motion using random dot cinematograms (Watamaniuk and Sekuler, 1992; Williams and Sekuler, 1984). We used the “Best PEST” (Lieberman and Pentland, 1982) method to derive the threshold level of noise at which direction can be detected. This experiment employed random-dot cinematograms in a two alternative forced choice presentation that varied in magnitude of mean direction, and duration. Each individual dot's path was varied by sampling from a probability distribution in which the standard deviation ranged from +/− 5 to 65 degrees from the primary direction. The magnitudes of mean directions between two presentations of each trial were 4, 7, 10 and 13 degrees. On each trial one presentation had a mean direction that was 20 degrees to the left or the right of an upward direction. The duration for each trial was either 500 or 1000 milliseconds. Four younger (average age of 25) participants and four older (average age of 75) individuals participated in our study. The subjects' task was to determine if the second presentation was to the right or left of the first. The results indicate main effects of age, duration, and direction difference magnitude. Noise thresholds decreased with increasing direction difference, and increasing duration. In general, older observers had elevated thresholds compared to younger observers, with less tolerance to direction noise at short durations.
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