I could see nothing sinister about him. I wondered if the fact that he was not drinking helped to set him off from his guests, for it seemed to me that he grew more correct as the fraternal hilarity increased.
Like, in one 2015 study, researchers asked hundreds of pairs of identical twins, who have close to the same set of genes, and fraternal twins, who don't, to rate the attractiveness of pictures of faces.
What got me into twin research initially is that I am a fraternal twin and always fascinated with the similarities and differences, mostly differences that my sister and I have.
On the other hand, if both fraternal and identical twins share a trait equally, chances are their environment, not their genes, influenced that particular trait.
When they exposed the twins to mosquitoes they found that identical twins were bitten in similar amounts but fraternal twins were bitten in differing amounts.
The identical twins found a few more of the same qualities attractive than the fraternal twins, but not enough to be entirely — or even mostly — explained by genetics.
If identical twins share a trait to a greater degree than fraternal twins do, it's safe to conclude that the relevant gene significantly influenced that trait.