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Alissa Jacobs, Jeannine Pinto, Maggie Shiffrar; Frequency, context, and human motion perception. Journal of Vision 2002;2(7):338. doi: 10.1167/2.7.338.
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© ARVO (1962-2015); The Authors (2016-present)
Does the visual perception of human movement benefit from our social interactions with other people? To investigate this question, we created point-light displays of human gaits that varied in unusualness. Under normal conditions, walkers automatically adopt the most energy efficient combination of stride frequency and amplitude for any given speed. Occasionally, humans might adopt an unusual stride frequency-amplitude combination (such as taking quick, short steps on hot sand). Hence, some gaits are frequently experienced while others are not. Is visual sensitivity to common gaits greater than visual sensitivity to unusual gaits? To answer this question, point-light walkers exhibiting both common and unusual gaits were created by videotaping one of two walkers on a treadmill. Stride frequency and amplitude were systematically manipulated across ten different speeds. Using a two-interval forced choice procedure, pairs of movies depicting the same walker at two different speeds were sequentially presented to naive observers. Walker speed differed by 0.5 or 1.0 km/hr. Subjects were asked to report which walker was walking faster. Speed discrimination did not significantly differ across variations in gait frequency, suggesting that human motion perception is not a function of experience with any particular movement. An identity discrimination task was then employed to determine whether frequency might influence a more socially relevant task such as our ability to identify individuals from their motion. Colleagues of the two models used in Experiment 1, and the models themselves, viewed the movies described above and judged the identity of each walker. Overall, models performed equally well with common and unusual gaits. With colleagues, performance was a function of the type and extent of social relationship with the model. Thus, experiential differences can influence biological motion perception under socially relevant contexts.
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