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Rebecca Woods; Toddlers' Discrimination of Shadow and Reflectance. Journal of Vision 2016;16(12):644. doi: 10.1167/16.12.644.
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© ARVO (1962-2015); The Authors (2016-present)
Studies investigating the development of shadow perception demonstrate that by 7 months, infants are sensitive to shadow information; they perceive depth from shadows (Imura et al., 2006; Yonas & Granrud, 2006) and detect incongruencies in an object's shape and the shadow it casts (Sato et al., 2015). However, distinguishing shadow patterns viewed on the surface of objects from patterns created by object properties (i.e., reflectance) in the absence of a visible caster is a more challenging task and one that has not yet been assessed in infants. The current study investigated the development of this ability using a preference task. Toddlers (23- and 30-month-olds, N = 32) were presented with two toy eggs, one with dots and the other without. The plain egg was opened to reveal an entertaining chirping bird. After initial exposure, the eggs were placed on a stage equidistant from the toddler (counterbalanced placement) in a baseline condition used to ascertain the child's initial preference. Test trials were identical except to simulate shadows, dots were projected on the surface of the plain egg. Selecting the correct toy required the child identify the plain egg even when the shadow pattern was projected onto it. Percent correct scores were analyzed using a one-way ANOVA revealing statistically significant differences by age at p < .001, ɳp2 = .41 with the older infants succeeding more frequently. Furthermore, the 23-month-olds' scores did not differ significantly from chance, t(15) = 0.22, p = .83 (M = 52%), whereas the 30-month-olds' did, t(15) = 18.15, p < .001 (M = 96%). These results indicate that only the 30-month-olds readily identified the egg with the chick inside, suggesting that the ability to distinguish shadow patterns from reflectance patterns in the absence of a caster emerges between 23 and 30 months of age.
Meeting abstract presented at VSS 2016
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