Do infants have requirements for perceiving shadows?
43.3041, Monday, 18-May, 8:30 am - 12:30 pm, Banyan Breezeway
Kazuki Sato1,2, So Kanazawa3, Masami Yamaguchi1; 1Department of Psychology, Chuo University, 2Japan Society for the Promotion of Science, 3Department of Psychology, Japan Womens University
The contrast polarity of shadows is a crucial factor for shadow perception. Cavanagh and Leclerc (1989) indicated two requirements for perceiving shadows: (i) shadows should be darker than non-shadow areas and (ii) the contrast polarity along borders of shadows should be consistent. We investigated whether the perception of shadows in 5- to 8-month-olds had satisfied these requirements. Previous studies showed that around 7-month-olds could perceive depth from attached and cast shadows (Granrud & Yonas, 1985; Yonas & Granrud, 2006). Hence, we hypothesized that the 7-month-olds can perceive shadows, meanwhile this perception has the same requirements as adults. We carried out two experiments to test this hypothesis. In Experiment 1, we tested whether infants could discriminate attached-shadow figures and cast-shadow figures which had a consistent contrast polarity firstly, and then tested the figures which had a reversed contrast polarity of shadow areas. The results showed that only 7- to 8-month-olds could discriminate attached- and cast-shadow figures not when the contrast polarity of shadow areas was reversed, but when the shadows were darker than background. In Experiment 2, we tested whether infants could detect the congruence between the shape of an object and its cast-shadow which had a consistent contrast polarity firstly, and then tested the figures which had an inconsistent contrast polarity by added white outlines to the shadow areas. The results showed that 7- to 8-month-olds could detect the incongruence between the shape of an object and its cast-shadow shape only when the contrast polarity along borders of shadows was consistent. In conclusion, we found that 7- to 8-month-olds possibly have two requirements for the perception of shadows as the same as adults.