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Laura A. Gibson, Javid Sadr, Nikolaus F. Troje, Ken Nakayama; Perception of biological motion at varying eccentricity. Journal of Vision 2005;5(8):16. doi: 10.1167/5.8.16.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Items in the periphery are harder to see than those in the fovea. The degree of difficulty depends on the task and stimuli used. We investigated the size threshold for determining a point-light walker's direction of motion both in the fovea and in the periphery. The rate at which this threshold increases as stimuli are shown farther into the periphery is described by the eccentricity (E2) at which a stimulus magnified to twice the size would show equivalent performance in the fovea. Method: Point-light treadmill walkers of different sizes were presented by method of constant stimuli at four levels of eccentricity: 0, 10, 20, and 40 degrees. Participants reported which direction the walker was headed (right or left) without feedback. Results: Threshold size was surprisingly small. Thus a six-foot walker's direction could be discerned at a distance of 1400 feet at the fovea and at about 85 feet at 40 degrees eccentricity. E2 values ranged from 3.1 to 3.8. Conclusions: In comparison to significantly lower E2 values for both simple and more complex form tasks, these high E2 values suggest that the periphery is more efficient in coding complex moving patterns. It is of interest to determine whether other perceived aspects of biological motion, for example gender, have similar E2 values.
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