The present study reports preliminary data from two unselected samples of carefully diagnosed autistic subjects (children and adults) and an assessment procedure that includes a large sample of items, appropriate for lower-functioning autistic subjects, with multiple presentations within and between sessions 1 week apart. The study seeks to determine (1) whether a raised incidence of non-right-handedness exists in these samples (2) if so, what constructs best represent this shift in the handedness distribution (i.e., phenotype and CNS substrate) and (3) whether these handedness phenotypes are associated with different levels of cognitive functioning. The results reveal a dramatic shift away from right-handedness in both autistic samples, due to a raised incidence of two phenotypes, manifest left-handedness and ambiguous handedness. The ambiguously handed, who were postulated to represent substantial bilateral CNS pathology due to early brain injury, were found to have much lower intellectual scores in one of the study samples. (Soper, H., Satz, P., Orsini, D. Henry, R. Zvi, J. & Schulman, M. (1986). Handedness patterns in autism suggest subtypes. Journal of Autism and Developmental Disorders, 16, 155-67.)
Uncovering the differences between brain injury autistics and those that are autistic because of combinations of genetic inclinations (random handed with little cerebral lateralization), environmental effects impacting testosterone and estrogen levels of mother and self, and conventional child rearing practices seem vital to coming to understandings. In other words, how does autism created by brain injury differ from autism created by genetics/environment? Are there studies out there experimenting with potential differences? How would you conclude a child is one but not the other? It’s near impossible until we prove how one of the two causes (brain injury vs genetics/environment can be proved.