Once upon a time, a mother and housewife name Judith Rich Harris, with a business on the side writing psychology textbooks, lost her faith. Which is to say, she turned against the prevailing school of thought of mainstream psychology at the time, which believed that early parental behavior exerted profound influences over a child's behavior and personality, and would influence their development throughout the rest of their lives. She wrote a book, 'The Nurture Assumption', which said essentially that children have their own disposition, their own personality, and there are some fairly stringent limits on what a parent can do to impact that. She published the book, it was reasonably successful, and then all hell broke loose.
Psychology, as a field, has a tradition going back at least to Freud of saying that our early childhood experiences are key to understanding our adult abilities (and neuroses). As a field (which is to say with some individuals who disagree) psychology likes to tell parents that if they perform their role well their kids will be mentally healthy, but if they screw up (in any of countless ways) their kids will be mentally scarred for life. Harris said, in effect, that there is such a thing as good enough parenting, and even if you do everything right as a parent it's still hard to predict turn out. Psychology did not like this, and Harris was pilloried for it.
She is back with a second book. It is not exactly a peace offering.
It should be pointed out that not all of the big names in psychology condemned Harris. Evolutionary psychologists such as Steven Pinker have come to her defense. But Harris clearly delights in her role as heretic, as seen from the viewpoint of Freud or Skinner, and she take multiple opportunities to relate tales of heated exchanges between herself and her detractors.
The starting point for her current book is the phenomenon of conjoined (also sometimes called Siamese) twins. They are genetically identical, and obviously have had the same environment, or at least as close as parents can possibly arrange for. Why do they have distinctly different personalities? If the difference in "environment" between conjoined twins is large enough to impact personality, that is more or less the same as saying that personality and ability can be impacted by environmental differences too tiny for parents ever to keep track of, and it might as well be random.
Which would be one fair answer. Harris thinks we can do better than "it's random", though, and she sets out to determine (in light of every study she can find on twins, siblings, half-siblings, and step-siblings) what is going on in human development, besides genetics. The current rule of thumb (until recently controversial) is that something just under half of the variation in personality and ability between people, is due to genetics.
The first half of the book, Harris disposes of five "red herrings", as she calls them. This involves convincing the reader of such uncomfortable truths as the fact that parental control of the environment inside the home doesn't affect much other than how the child behaves inside the home. People wish to believe (whether they identify with the role of parent or grown-up child looking back) that how parents run their home shapes how the child raised there turns out. Aside from pathological cases of horrific abuse, there is little evidence that this is so, and much that it is not so.
The second half of the book involves Harris putting forth her model (hint: it's grounded in evolutionary psychology and game theory). I am not prepared to pronounce judgment on it at this point; it sounds plausible, and testable, but I'm not in a position to test it myself. Hopefully, the gauntlet she has thrown down to the psychology community will be picked up by a researcher or three (Harris has health issues which prevent her from doing the research herself, and in any event no one should be trusted to test their own publicly stated hypothesis).
So, how does it all read?
Despite the frequent references to research performed by others, Harris' personality definitely shines through. When a few hundred pages into the book, she says "as a child I flunked socialization", we are not surprised. If you like to read of the slaughtering of the sacred cows of the ivory tower (<-mixed metaphor), Harris is likely to please.
One quibble: she likes to quote from her favorite works of fiction (Arthur Conan Doyle, Sue Grafton, Josephine Tey), in a way which I'm sure she thinks is meant to illustrate but which I found distracting. Perhaps for the reader who is less tolerant of study citation after study citation, the occasional literature or pop culture reference is more welcome. I consider it a minor blemish.
Overall, "No Two Alike" is a thought-provoking and highly readable book. It's packed with references, with enough details in the main text to back up what she is saying is or is not so. She is taking on some fairly deep-rooted beliefs, things we WANT to be true, and showing us that they are not all true, and this is something I always respect (whether I agree in the end or not). Her work straddles the line between popular science and original work (because her models of human development yield testable predictions), in more than one way, because she is in many cases drawing psychology's attention to the consequences of its own researchers' work. It will take time (and further research) to see if Harris is a visionary or an entertaining crank, but in either case, her book is worth reading, and thinking about.