Infants' looking times in a 2-D mental rotation task

Abstract

In adults, substantial and consistent sex differences during mental rotation favouring men are obtained as long as certain methodological boundary conditions are met. In recent years, a number of studies using different stimuli and experimental approaches investigated sex differences in mental rotation in infants with inconclusive results. The goal of the present study was to examine on the basis of a sufficient statistical power (a) whether infants aged 6 month are able to use mental rotation in a preferential looking task after familiarization with simple 2-D stimuli; (b) whether there were sex differences present, and (c) whether the results depend on inducing an expectation about the orientation of the upcoming stimulus. Our data suggest that the familiarization paradigm is well suited to reveal sex differences in mental rotation favouring boys only when it induces an expectation about the orientation of the upcoming stimulus. If no such expectation is induced, neither boys nor girls reveal evidence for mental rotation. More studies are needed to evaluate sex differences in infancy and, more importantly, whether infant's sex differences are restricted to experimental paradigms that induce the extrapolation of an induced rotary movement. Highlights: We investigated the reliability of recent findings suggesting that male but not female infants show evidence for mental rotation although no expectation about the orientation of the upcoming stimulus was possible. By measuring the novelty preference in looking times, we found no evidence for mental rotation and no evidence for a sex difference as long as no expectation about stimulus orientation was possible. Since the sex effect was only present when an expectation of stimulus orientation was induced, the ability of rotary extrapolation might be the reason for sex effects sometimes present in infant research on mental rotation.