Originally posted on September 30, 2014.
Behavior geneticists have gifted us with two stunning findings—discoveries that overturned what I used to believe about the environment’s power to shape personality. One, dramatically illustrated by the studies of identical twins separated near birth, is the heritability of personality and intelligence. The other, dramatically illustrated by the dissimilar personalities and talents of adoptive children raised in the same home and neighborhood, is the modest influence of “shared environment.”
I know, I know . . . studies of impoverishment during the preschool years, of epigenetic constraints on genetic expression, and of family influences on attitudes, values, and beliefs, remind us that genetic dispositions are always expressed in particular environments. Nature and nurture interact.
And might identical twins have similar personalities not just because of their shared genes, but also their environments responding to their similar looks? If only there were people who similarly look alike but don’t share the same genes.
Happily there are unrelated look-alikes—nontwin “doppelgängers” identified by Montreal photographer François Brunelle (do visit some examples here). California State University, Fullerton, twin researcher Nancy Segal seized this opportunity to give personality and self-esteem inventories to these human look-alikes.
Unlike identical twins, the look-alikes did not have notably similar traits and self-esteem (see here). And in a new follow-up study with Jamie Graham and Ulrich Ettinger (here), she replicates that finding and also reports that the look-alikes (unlike biological twin look-alikes) did not develop special bonds after meeting their doppelgänger.
The take-home message. Genes matter more than looks. As the evolutionary psychologists remind us, kinship biology matters.