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-monthold infants to an object revolving through a 240° angle. In successive test trials, infants saw the habituation object or its mirror image revolving through a previously unseen 120° angle. Only the male infants appeared to recognize the familiar object from the new perspective, a feat requiring mental rotation. These data provide evidence for a sex difference in mental rotation of an object through three-dimensional space, consistently seen in adult populations.Fifty years of research has confirmed that men typically outperform women in spatial-ability tests (Linn & Petersen, 1985;Voyer, Voyer, & Bryden, 1995). Such sex differences have been detected in 4-year-old children (Levine, Huttenlocher, Taylor, & Langrock, 1999); in children under 13, these differences are most often found on tasks requiring mental rotation (Voyer et al., 1995). Mental-rotation tasks revealing the largest sex differences require subjects to view a two-dimensional (2-D) representation of a three-dimensional (3-D) object, and to then recognize a novel 2-D representation of the same object rotated into a different orientation in 3-D space (Levine et al., 1999). Effect sizes for sex differences on such tasks are typically larger than the effects of sex on other behaviors (Collaer & Hines, 1995).The current study examined the origins of mental rotation in infancy. Early work revealed that 4-month-old infants can detect the 3-D form of objects moving around two axes of rotation (Kellman, 1984;Kellman & Short, 1987). More recent studies presented infants with kinetic random-dot displays that specified rotating 3-D cubes (Arterberry & Yonas, 2000) and with video displays of partially occluded 3-D shapes rotating around a vertical axis (Johnson, Cohen, Marks, & Johnson, 2003); in both cases, 2-month-old infants appeared to perceive the 3-D shape of rotating objects.Other studies found that 4-month-old infants form dynamic mental representations that allow them to both track the movement of a 2-D object rotating in the frontal plane and anticipate the object's ultimate orientation (Rochat & Hespos, 1996;Hespos & Rochat, 1997). These results were interpreted as tentative evidence for rudimentary mental rotation in infants; however, although these results suggest that infants can use exposure to a moving 2-D object to help them predict how that object will look when rotated in a 2-D plane, fullblown mental rotation has traditionally been tested by requiring observers to mentally rotate 3-D stimuli through 3-D space and to discriminate the rotated object from its mirror image (Shepard & Cooper, 1982). No studies have yet provided evidence that infants can recognize a particular 3-D object-as distinct from its mirror image-after it has been rotated through 3-D space into a previously unseen perspective; such an ability would be indicative of Address corr...

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SummaryStatistical education now takes place in a new social context. It is influenced by a movement to reform the teaching of the mathematical sciences in general. At the same time, the changing nature of our discipline demands revised content for introductory instruction, and technology strongly influences both what we teach and how we teach. The case for substantial change in statistics instruction is built on strong synergies between content, pedagogy, and technology. Statisticians who teach beginners should become more familiar with research on teaching and learning and with changes in educational technology. The spirit of contemporary introductions to statistics should be very different from the traditional emphasis on lectures and on probability and inference.

Mental rotation involves transforming a mental image of an object so as to accurately predict how the object would look if it were rotated in space. This study examined mental rotation in male and female 3-month-olds, using the stimuli and paradigm developed by Moore & Johnson (2008). Infants were habituated to a video of a 3-dimensional object rotating back and forth through a 240° angle around the vertical axis. After habituation, infants were tested both with videos of the same object rotating through the previously unseen 120° angle, and with the mirror image of that display. Unlike females, who fixated the test displays for approximately equal durations, males spent significantly more time fixating the familiar object than the mirror-image object. Because familiarity preferences like this emerge when infants are relatively slow to process a habituation stimulus, the data support the interpretation that mental rotation of dynamic 3-dimensional stimuli is relatively difficult—but possible—for 3-month-old males. Interpretation of the sex differences observed in 3- and 5-month-olds’ performances is discussed.