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Sathyasri Narasimhan, Deborah Giaschi; The Effect of Dot Speed and Density on the Maturation of Global Motion Perception. Journal of Vision 2011;11(15):53. doi: https://doi.org/10.1167/11.15.53.
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Global motion stimuli are commonly used to study motion perception, including its development, in human and nonhuman primates. The age at which this aspect of motion perception matures to adult levels is currently a point of contention, with published values ranging from before 3 years of age (Parrish et al., 2005) to after 12 years of age (Lewis et al., 2010). Specific stimulus attributes such as dot speed and density vary considerably across previous studies, which may explain the conflicting results. We measured coherence thresholds for global motion direction discrimination in 5 year-old children and in adults (18–23 years) at two dot speeds (1 and 4 deg/s) and three dot densities (1, 15, 30 dots/deg2). Adult coherence thresholds were constant at approximately 10%, regardless of speed or density. Child coherence thresholds were significantly higher, and were most immature at the slow speed and at the sparsest density. The speed finding confirms previous results (Ellemberg et al., 2004; Hayward et al., 2010). The novel density finding can account for much of the discrepancy in the current developmental literature. These results caution against drawing firm conclusions about visual maturation or deficits in clinical populations based on only a single measurement at a specific combination of speed and density.
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