Four papers reinforce the generality of this conclusion [11•,12•,13•,14•]. All four deal with a field known as imaging genetics, that is the study of association between genetic variants and phenotypes obtained from structural and functional imaging of the brain (almost all studies are of human brains and the majority employ magnetic resonance imaging modalities). An important conclusion to emerge from these papers is that the genetic loci influencing imaging genetic phenotypes “have comparable effect sizes to those observed in other genome-wide association studies of complex traits” [11•]. To take one example, the rs10784502 marker is associated with 0.58% of intracranial volume per risk allele [11•]. The implications of this finding, and the other insights into the genetic architecture of behavior we have discussed, become clear when we turn to look at the second focus of our review.
