Laura Rodgers with Dr. Morton Gernsbacher

UW-Madison Department of Psychiatry

Low 2D:4D digit ratios are a proxy for high prenatal testosterone levels. Hand scans of children diagnosed with Autism Spectrum Disorder by the Twin Autism Project were utilized to find 2D:4D digit ratios of autistic twins in Wisconsin. My individual project, which was one segment of the broader Twin Autism project, involved an analysis of the way prenatal testosterone (indicated by the 2D:4D digit ratios) is related to zygosity and autistic concordant/discordant twins. As expected, our analysis revealed that monozygotic twins are much more likely to be concordant for autism than dizygotic twins. This indicates that genetics plays a much larger role in autism than prenatal conditions. More tests relating to the dizygotic twin pairs did not reveal statistically significant relationships between autism, digit ratios or zygosity.  One limitation of the study is that the sample consisted only of twins where at least one of the pair had been diagnosed as autistic. Therefore, the only non-autistic individuals in the sample were either genetically identical (in the case of monozygotic twins) or similar (in the case of dizygotic twins) to another individual who was autistic.  The most plausible explanation for our failure to find statistically significant relationships between autism, digit ratios or zygosity is the fact that it was not possible with this sample of autistic twins to control for the effects of genetic similarity.