Judith Harris, author of the previously reviewed The Nurture Assumption, follows up with another book on personality development, No Two Alike. This has the same strengths and flaws as the previous work; Ms. Harris makes good points but doesn’t present her arguments in an organized fashion. In this case, she’s going after explanations for human personality; again nature/nurture; birth order; genetics; and etc. She uses the unfortunate analogy to a detective story – which means rather than a dry but clear exposition we get a whole book full of red herrings before Harris explains her hypotheses: human personality is formed by the combination of innate systems and experience. The innate systems are a relationship system that allows us to tell family from strangers, a group socialization system that allows us to “fit in” to a group, and a status system that allows us to determine where we rank in various social groups. And she leaves this as a hypothesis, challenging the field to falsify it; i.e. the “detective story” is left with a principal suspect but no arrest or conviction.


Still, despite the wandering around and the imperfectly satisfying conclusion there’s a lot to like about No Two Alike. With The Nurture Assumption, Harris became the academic psychology equivalent of the pajamaheddin who exposed the CBS/Rather Bush National Guard memo hoax. In No Two Alike a good part of the book’s first few chapters is devoted to Harris’ response to various academic attacks. Harris is confined to home with a debilitating disease and does her research from there; it was very imprudent for more traditional academics to dis’ somebody who is obviously very smart and who has a lot of time on her hands. Her detractors quoted various studies and ongoing but not yet published research (she fits this into her “detective story” theme by citing Josephine Tey’s The Daughter of Time, which features a Scotland Yard inspector solving a very old case – the murder of the Princes in the Tower – while confined to a hospital bed). Harris tracked down all the studies thrown at her and demonstrated that they either didn’t say what the critics claimed they said or that they had ignored various confounding factors; and the not yet published research never showed up in her inbox even when repeatedly requested. And she names names, which has to be disconcerting for the named.


Other features include a nice dissection of “birth order” personality theories; the observation (also made frequently in The Nurture Assumption) that psychology researchers frequently fail to establish the direction of causality (are children well behaved because they get a lot of parental affection, or do they get a lot of parental affection because they are well behaved?); and overgeneralization of some studies (parenting methods that improve behavior at home do not improve behavior elsewhere, and vice versa).


One big improvement on The Nuture Assumption: endnotes rather than page number references, making it much easier to check Harris’ data. ( )

Good, but not as novel or interesting as Nurture Assumption

This is book is about the origin of personality differences in people, which Ms. Harris presents as something of a detective story. She begins by noting the surprising, but well known facts: identical twins raised separately are no less alike than raised together: unrelated siblings are no more alike when raised together than when raised apart. Evidently the home environment, parenting practices, nor siblings have anything to do with the variation of personality. She also discuses the well-known fact that personality is partly genetically determined (comes from the biological parents). Now she asks, where does the other part of the variation come from? Is it the peer group (as she suggested in her previous book) or is there some other source to be discovered?

She presents the story in a quite lively, readable manner, and I enjoyed it very much. I enjoyed her encounters with the "establishment" and the revealing stories about her rivals. There are, no doubt, more than one side to these things, but she is not obliged to tell them in this sort of work.

To answer her question, she describes several "modules" in the brain that are important in forming the personality. I found her resolution quite unsatisfying: she might have as well said that the origin of the variation was due to noise, or random factors, not under the control of anything at all. I don't see how positing their existence, which is entirely plausible, explains the variation at all. She sets forth no testable hypothesis based on this assumption, so far as I can see.

If you want to know the answer to her question, don't bother with this book. On the other hand, if you want an interesting book on personality and how evolutionary psychologists view it, and work on it, this could be the book for you. ( )