Hand preference and hand skill were assessed in 20 children with autism, 20 normal controls and 12 children with mental retardation. 90% of the normal controls and 92% of the children with mental retardation showed concordance for hand preference and hand skill (i.e. the preferred hand was also the more skillful), whereas only 50% of the children with autism showed concordance of preference and skill, the remaining 50% preferring to use the hand which was less skillful. Children with autism also showed a lesser degree of handedness and a lesser degree of consistency than the other groups, although this was unrelated to the discordance of skill and asymmetry. A developmental model of handedness is proposed in which the development of handedness as preference is ontogenetically prior to the development of handedness as skill asymmetry, such that in normal children the development of skill asymmetry occurs as a secondary consequence of the establishment of preference. The causal sequence is disrupted in autism, so that although preference is established, it does not subsequently result in concordant skill asymmetry. (McManus, I. C., Murray, B., Doyle, K. & Baron-Cohen, S. (1992). Handedness in childhood autism shows a dissociation of skill and preference. Cortex, 28(3), 373-81.)
There are differences in handedness amoung varying cultures around the world. Asian societies display around 2%. It is not clear how much of this is due to its being discouraged. Some American Aboriginal populations show 12% left handedness (Canadian Northwest populations).
What’s at issue here is the relationship between handedness, maturational delay, and autism. If there are variations among the autistic between those that use a hand that is more adept and those that do not, with more autistics using the left hand than the general population, then perhaps the autistic are more guided by Annett’s right shift theory with their being random handed to such a degree that choosing a less adept hand is not inhibited.
A question would be, among those NW Indian tribes, do they also often choose to emphasize a hand that is less adept?