Dr. Daniel MacArthur points to a long article by Edmund Yong, Dangerous DNA: The truth about the 'warrior gene'. Dr. MacArthur notes on his twitter account: "Nice piece on behavioural genetics...but should emphasize MOST behav. gene assocs are actually false." I think he's pointing to the winner's curse; there are lots of people studying various topics, but only a subset of studies pass which yield appropriate effect sizes and p-values actually get published. A sequence of such may give a false sense of certitude as to the strength of the association between a locus and a trait, as negative results are not usually published. I hope David Dobbs keeps this in mind in relation to his new book on the 'orchid hypothesis'. We have decades of research which suggest that a lot of human behavior is due to variation in genes within the population. In other words, many psychological traits and predispositions are heritable. But both the earlier linkage studies and now the associations which try and establish a particular gene as the primary causal factor are much more provisional, and like much of science wrong or ultimately of marginal long term value. The incredible amount of press which genetics and genomics research with behavioral implications receive in the press is more about our psychology than the state of science as it is now. Similarly, consider the enormous swell of neuroimaging research within the past decade. Both genetics and neuroscience offer up the possibility of establishing a sturdier biophysical grounding for the human sciences, but we shouldn't get ahead of ourselves. Finally, the fact that we know that psychological traits are heritable is useful in and of itself, whether we know the underlying genetic architecture of the trait or the neurobiology mediating between the genetic and behavioral level. Look to the parents, and you shall know a great deal.