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Terri L. Lewis, Lisa R. Betts, Daphne Maurer; The Development of Sensitivity to the Direction of Motion. Journal of Vision 2012;12(9):485. doi: https://doi.org/10.1167/12.9.485.
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© ARVO (1962-2015); The Authors (2016-present)
Last year (VSS 2011), we reported that, under most conditions, sensitivity to differences in direction of motion improves dramatically between 5 and 7 years of age, with a smaller improvement between age 7 and adulthood. This was true for smaller dots (diameter = 2.5 arcmin) moving relatively slowly (4.16º/s) or quickly (8.65º/s) and for larger dots (diameter = 10 arcmin) moving quickly. Surprisingly, adults performed poorly when the larger dots moved slowly—their minimum discriminable deviation from vertical (10.3º) was worse than that of 7-year-olds (4.7º) and no better than that of 5-year-olds (10.4º). We speculated that this poor performance in adults, but not 7-year-olds, might be related to the onset of inhibitory mechanisms after age 7 (e.g., Tadin et al., 2003). To estimate when these inhibitory mechanisms might become adult-like, we are using the same procedure with older children. As before, observers indicated on each 1s trial whether the dots moved to the left or right of a vertical reference line. We used a 3-down, 1-up staircase to measure the minimum deviation discriminated from vertical for the smaller and larger dots moving at the slower or faster speed. Sensitivity was adult-like in three of four conditions by 9 years of age (n = 20/grp; ps > 0.05). However, for the large (10 arcmin) slowly moving (4.16º/s) dots, 9-year-olds (2.8º) were significantly better than both 7-year-olds and adults (ps <0.01). Preliminary results from seven 12-year-olds and ten 15-year-olds show that thresholds begin to increase toward adult values after age 12. However, even at age 15, thresholds for the large, slow dots are still ~2.5 times better (4.2°) than those of adults (10.4°). The results suggest that inhibitory mechanisms that limit adults’ performance for large, slowly moving stimuli may continue to mature throughout the teenage years.
Meeting abstract presented at VSS 2012
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