Abstract

After seeing a 2-dimensional (2D) representation of a 3-dimensional (3D) object, adults can recognize a novel 2D representation of that object rotated in space; the ability to recognize the object is commonly thought to require a process called “mental rotation.” Since the 1970s, a sex difference on mental rotation tasks has been demonstrated repeatedly, but not in children less than 4 years of age. To demonstrate mental rotation in human infants, we habituated 5-month-old infants to an object revolving through a 240-degree angle. In successive test trials, infants saw the habituation object or its mirror image revolving through a previously unseen 120-degree angle. Only the male infants appeared to recognize the familiar object from the new perspective, a feat requiring mental rotation. We subsequently tested a group of 3-month-old infants, and although the results were somewhat different, we continued to find a sex difference that we interpret as meaning that male infants were able to mentally rotate the habituation stimuli. These data provide evidence in infants for a sex difference in mental rotation of an object through 3D space, consistently seen in adult populations. See also Moore, D. S., & Johnson, S. P. (2008). Mental rotation in human infants: A sex difference. Psychological Science, 19, 1063-1066.