That 50% number keeps coming up, this time in a Nature article "Genomic analysis of family data reveals additional genetic effects on intelligence and personality." Two things to note: this doesn't mean that the other 50% is environmental. To date, very little can be shown to be environmental with the strength that this study shows for genetics. The remaining 50% is "other," and seems to be uncomfortably random. A Tom Stoppard world.
The second point to be alert to is that personality characteristics are being measured with more rigor and confidence, and these will increasingly enter the discussion of heritability
(HT: Steve Sailer)