Do you know of any studies investigating whether there is a correlation between a child's physical resemblance of one parent and that child's similarity in personality to that same parent? e.g. Al looks much more like Dad and has his laid back personality, while Al's brother Bob looks much more like Mom and has her lively personality.

Assuming that Bob really is Dad's son, of course ...

I don't know, but this is a good question because it could help get at an idea that has been lingering for a long time — are differences in looks associated with differences in behavior? If so, why?

Greg Cochran has a strong aversion to Darwin's theory of sexual selection (not because it's never true — it is in some cases — but because it gives too easy an out for explaining physical differences: "Somebody must have thought it looked purty.") He suspects, for example, that fair hair and fair skin were less selected for in themselves than that they were by-products of something else that was being selected for in Europe.

Looking at siblings who look different, especially fraternal twins, might provide some evidence on this subject.