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Alejo Freire, Daphne Maurer, Terri L. Lewis, Randolph Blake; Adults are better than 6-year-olds at perceiving biological motion in noise. Journal of Vision 2004;4(8):235. doi: 10.1167/4.8.235.
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We compared the processing of biological motion by 6-year-olds and adults (n=16 per group) in two forced-choice discrimination tasks. Participants discriminated point-light biological motion stimuli from scrambled versions of the same actions. Stimuli consisted of black dots, each 10 arc min, moving on a gray background within a 20 × 15 deg window. Each dot depicted movement of a light placed at each major joint and the head of an actor performing one of twelve possible actions. Scrambled stimuli were equivalent to biological motion stimuli in terms of the movement of individual dots, but the movements were disrupted in terms of temporal phase and spatial location. Each display lasted 1 sec. The two tasks were: (i) No Noise: each trial presented a biological motion stimulus or a scrambled stimulus; and (ii) Noise: each trial presented a biological or a scrambled stimulus embedded in a mask composed of a variable number of dots; the number of masking dots was varied according to a staircase procedure, to determine the maximum number of masking dots yielding 71% accuracy. Masking dots each underwent equivalent motion to one of the dots in the biological motion display. Six-year-olds performed equivalently to adults in the No Noise task, consistent with a prior study in which 5-year-olds performed as accurately as adults in the absence of noise dots (Pavlova et al., 2001). However, children were not as sensitive as adults to biological motion presented in noise: at the estimated threshold, adults tolerated 30% more noise dots than children. Thus, extrastriate structures involved in biological motion processing are still immature at 6 years of age. Our findings of immaturities persisting into middle childhood are consistent with studies of other abilities dependent on extrastriate structures, namely processing of global form (Lewis et al., in press), of second-order relations in faces (Mondloch et al., 2002), and of contour integration (Kovács et al., 1999).
Canadian Institutes of Health Research grant # MOP-36430; National Institutes of Health Research grant # EYO7760
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