Does the genetic expression of specific physical traits ever correlate to behaviour? Over at skeptics, there were a couple questions asked as to the correlation of specific physical traits in relation to personality/behaviour. For instance, the simian line as well as red hair. Now, I did my best to answer these questions, with what I understand as there being a long history of people attempting to correlate external physical characteristics with behaviour (see the disgraced "art" of phrenology for instance). However, in answering the simian line question, I did come across some weak correlations. It got me to wondering if this is an area of exploration in terms of perhaps one gene sequence for a physical trait somehow being tied with another gene sequence for behaviour. So, do any physical characteristics being expressed through genes correlate to behaviour?

Aldridge et al. (2011) show a correlation between facial phenotypes and autism spectrum disorders (ASD) in a sample of 8-12 year old boys.

They studied two groups of boys, 65 that had been diagnosed with ASD and 41 who had not. They collected 3D images of the faces and looked for similar patterns among the two groups. They found a significant association between some phenotypes and ASD. But, as with most studies, the results are complex; there a distinct sub-groups within the ASD group.

Keep in mind that this is an association study -- no causation is shown.