Judith Rich Harris, _No Two Alike: Human Nature and Human Individuality_

HARRIS BEGINS HER book with the story of conjoined Iranian twins who decide to undergo a very dangerous operation--tragically, they do not survive--because, being interested in different things and not even wanting to live in the same town, they wish to be separate.

Since, as identical twins, they are genetically virtually the same, and since, being conjoined, they had the same upbringing, how did they wind up with quite distinct personalities?  That's the question.

Identical twins, it turns out, tend to wind up as different from each other in personality as any other siblings, shared genes and shared upbringing notwithstanding. This goes to show, Harris argues, that something else is having some large kind of impact on personality: not the parents or family so much as other people (peers especially), who distinguish (are designed to distinguish) even twins, begin to respond to them differently, have different expectations of them, make different assumptions about them, and so on, creating for each twin, in effect, his or her own world, in response to which he or she develops a distinct personality.

As with The Nurture Assumption, Harris's previous book (which I haven't read, only read about), No Two Alike goes to show that parental behavior influences their children a whole lot less than we usually imagine it does. As long as the parent is providing an ordinary amount of care (e.g., not locking your kids up in a closet for days at a time), then the community is going to play roughly as decisive a role as genetic inheritance is, whatever environment the parent is providing.

The argument struck me as persuasive. In the words of one mother of my acquaintance, whose daughter was a straight-A student from grade school on, modest, well-behaved, utterly reliable, and whose drug-dabbling son was seemingly unable to finish anything he started, "I'd rather not take any credit for [daughter] because then I would have to take the blame for [son]."

Just as interesting as Harris's argument are her stories of working as an independent scholar.  Without an institutional base or traditional academic credentials, hence liable to quick dismissal by various experts, she nonetheless has the patience to sift through the details of innumerable studies, sometimes crossing disciplinary lines, and thus is sometimes able to catch said experts taking an intellectual short cut or two, or resorting to bullying, or just plain acting in bad faith. I don't know that she is actually such an  underdog as she paints herself here--after all, she is a bestselling author, has won a few honors, and hangs out with the likes of Steven Pinker--but the stories herein of felled Goliaths make good reading.