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Tomoko Imura, Masami K. Yamaguchi, So Kanazawa, Nobu Shirai, Yumiko Otsuka, Masaki Tomonaga, Akihiro Yagi; Perception of 3-D shape from moving cast shadow in human infants. Journal of Vision 2006;6(6):376. doi: 10.1167/6.6.376.
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© ARVO (1962-2015); The Authors (2016-present)
Motion of cast shadow improves the perception of motion trajectory of the objects (Kersten, Mamassian, & Knill, 1997). Our previous studies showed that moving cast shadow was also effective for 6- and 7-month-old infants to perceive the spatial layout of objects (Imura et al., 2005), however, there are no developmental studies about 3-D shape perception from moving cast shadow. The present study attempted to examine whether infants aged from 4- to 7-month-old discriminate between two 3-D objects' shapes from moving cast shadows using habituation-dishabituation procedure. While an expanding ellipse without a cast shadow is perceived as no rigid and ambiguous for adult observers, manipulating the motion and shape of cast shadows occur two different three-dimensional impressions of objects although the their shapes are identical: one is raising “capsule”, and the other is expanding objects like “gum”. During habituation phase, infants were presented two identical expanding objects without shadows side by side, and then they were tested “capsule” and “gum”. If infants perceive the expanding objects as no rigid objects, they will prefer to look more the “capsule”, containing novel 3-D objects, than “gum” during test. The 6- and 7-month-old, but not the 4-and 5-month-old, infants looked significantly longer “capsule” than “gum”. These findings suggest that 6- and 7-month-old infants discriminate between two objects' shapes during test. These results revealed that depth perception from cast shadow develops around 6 months, and it is consistent with other pictorial depth cues.
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