Developmental coordination disorder affects 5% to 8% of the general population, and about 50% to 60% of these children have a comorbid attention-deficit disorder with hyperactivity and learning disorders. Left-handedness is relatively common among children with dyslexia, learning disabilities, and autism; however, its frequency in children with developmental coordination disorder is less clear. The present study investigated the distribution of hand dominance in 98 children (age range, 5.5-17 years) with developmental coordination disorder compared with their parents or siblings. Thirty children (30.6%) were left-handed and 13 (13.3%) were ambidextrous. The prevalence of left-handedness among their parents and siblings was similar to that of the general population. The results suggest that children with developmental coordination disorder, like children with learning disorders and deficit disorder with hyperactivity, present with higher frequency of left-hand dominance compared with the general population. (Goez, H. & Zelnik, N. (2008). Handedness in patients with developmental coordination disorder. Journal of Child Neurology, 23(2), 151-4.)
Until recently I hypothesized that the relatively common appearance of autism in first born children was that perhaps first borns had more stressful births than later borns, and that this might be a different kind of autism than that which features maturational delay. I estimated one way to tell the difference was if digital abilities in autistic newborns was inhibited suggesting a cerebral palsy like infirmity. This would be different than the kind of autism that comes to women giving birth to children at the end of the ability to get pregnant.
There might be some truth in this, but recent work by Sarah Blaffer Hrdy suggests that new borns, with no older siblings, raised in Western households with often only mothers as an integral other, don’t as easily develop theory of mind.
As regards the theory above, perhaps autism that emerges from different causes could be parsed out by differences in digital facility. Perhaps those traumatized exhibit a different effortless use of fingers and limbs than those without an environment that encourages theory of mind.