Asymmetry in the detection of shapes from shading in infants
Tomoko Imura, Masaki Tomonaga, Masami K. Yamaguchi, Akihiro Yagi
We investigated 3- and 4-month-old infants' sensitivity to differences defined by shading using a paired-comparison familiarity/novelty preference procedure. Infants were familiarized with a pair of displays consisting of homogeneous shaded disks, and then were tested with two displays: the familiar display and a novel one containing shaded disks with reversed polarity (defined as the target). Experiment 1 examined two assumptions on discerning shapes from shading in infants by manipulating the orientations in the shading gradient of stimuli. When the orientation of the shading gradient was vertical, 4-month-old infants looked at the novel display for a longer time during the test trial. However, they failed to detect differences when the orientation of shading gradients was horizontal. Three-month-old infants did not detect differences in either orientation of the shading gradient. Experiment 2 examined asymmetry in the detection of convex versus concave shapes. Four-month-old infants failed to detect the target when the orientation of the shading grating was vertical and the target was convex. Taken with the results of Experiment 1, concave shapes were much easier to detect than convex shapes for 4-month-olds. This asymmetry suggests that 4-month-old infants process shading information in the same manner as adults.
asymmetry, infants, pictorial depth cues, shape from shading