Hemispheric specialisation, spatial activity experience, and sex differences on tests of mental rotation ability.

A sex difference in mental rotation ability is well established. Among the explanations offered for this difference are that males are more frequently right hemisphere specialised for spatial processing and that they receive more spatial processing experience because of the sex stereotyping of activities involving spatial ability that exists in Western societies. Several studies have shown that males do report more spatial activity experiences on the Spatial Activity Questionnaire of Newcombe, Bandura, and Taylor (1983) and that such experience does correlate with performances on tests of mental rotation.

A large-scale study of handedness and pregnancy/birth risk events: implications for genetic theories of handedness.

Whether left-handedness is due to genetic factors or to pregnancy and birth stress events is an important question for models that attempt to explain the origins and distribution of human handedness. Major genetic theories of handedness, such as those of Annett (1985) and McManus (1981), allow for a nondetermination of some left- or right-handedness by "chance", but they hold that "pathological left-handedness", specifically, is of minimal influence. On the other hand, theorists such as Bakan (1971) and Coren (1995) take the view that right-handedness is a universal human characteristic, presumably due to a polygenic influence, and that left-handedness is essentially always the product of pregnancy and birth risk factors.

An X-linked three allele model of hand preference and hand posture for writing.

This paper describes a genetic model of hand preferences for writing and for handwriting posture (HWP). The challenge of devising an X-linked model for these aspects of human handedness was posed by the results of a large family handedness study (McKeever, 2000) that showed evidence of such linkage. Because X-linkage for handedness has been widely regarded as untenable, the prospects for developing such a model were not initially encouraging, but ultimately a viable model did suggest itself.