Development of illusory-contour perception in infants

We investigated whether infants from 8-22 weeks of age were sensitive to th e illusory contour created by aligned line terminators. Previous reports of illusory-contour detection in infants under 4 months old could be due to i nfants' preference for the presence of terminators rather than their config uration. We generated preferential-looking stimuli containing sinusoidal li nes whose oscillating, abutting terminators give a strong illusory contour in adult perception. Our experiments demonstrated a preference in infants 8 weeks old and above for an oscillating illusory contour compared with a st imulus containing equal terminator density and movement. Control experiment s excluded local line density, or attention to alignment in general, as the basis for this result. In the youngest age group (8-10 weeks) stimulus vel ocity appears to be critical in determining the visibility of illusory cont ours, which is consistent with other data on motion processing at this age. We conclude that, by 2 months of age, the infant's visual system contains the nonlinear mechanisms necessary to extract an illusory contour from alig ned terminators.