Number versus contour length in infants' discrimination of small visual sets

This study examined infants' use of contour length in number discrimination tasks. We systematically varied number and contour length in a visual habituation experiment in order to separate these two variables. Sixteen 6- to 8-month-old infants were habituated to displays of either two or three black squares on a page. They were then tested with alternating displays of either a familiar number of squares with a novel contour length or a novel number of squares with a familiar contour length. infants dishabituated to the display that changed in contour length, but nor to the display that changed in number: We conclude that infants base their discriminations on contour length or some other continuous variable that correlates with it, rather than on number.