Judith Rich Harris once had a job writing psychology textbooks. She’d been kicked out of Harvard before earning a Ph.D. and suffered from chronic health issues, and this was something she could do from home.

Then she quit that job, having decided to upend the field rather than “teaching the received gospel to a bunch of credulous college students.”


Like many people through the ages, psychologists in the 1990s believed that parents play a major role in shaping their kids’ abilities and personalities. These scientists published lots of studies on the importance of “parenting styles”; the more commercially minded among them published books telling parents how to get it right.

In her research, though, Harris kept coming across work that strongly contradicted this type of thinking — particularly from a growing field called behavioral genetics, which took a special interest in siblings, including unusual kinds of siblings such as twins and adoptees. These studies showed that genes, not the “shared environment” that parents take pains to provide and perfect, are the biggest reason that siblings are similar to each other. In general, identical twins are remarkably similar whether they’re raised together or not. And adoptive siblings are not much more similar than strangers despite sharing an environment.

Harris put together an article, published in a top academic journal in 1995, that started this way: “Do parents have any important long-term effects on the development of their child’s personality? This article examines the evidence and concludes that the answer is no.”



And in her engaging 1998 book The Nurture Assumption: Why Children Turn Out the Way They Do, Harris brought this idea to the masses, arguing that parents should chill out. Moms and dads need to provide the essentials of a healthy and enjoyable childhood, she wrote, but beyond that, their day-to-day decisions just don’t seem to have dramatic long-run effects. There are many complicating nuances to the findings that Harris placed under the spotlight, but the basics are extremely well established and have held up in the two decades since.

It would be hard to overstate Harris’s influence, even if plenty of people still resist her conclusions. (After years of begging I still can’t get my wife to read the book.) Harris’s ideas show up everywhere from Steven Pinker’s The Blank Slate to Bryan Caplan’s Selfish Reasons to Have More Kids; just a week and a half ago they echoed rather strongly in a think-tank report about early childhood development. They’ve shown up plenty in my own writing as well.

Newer research, of course, is digging even deeper into the effects of genes on our personalities and abilities. (See Razib Khan’s review of Robert Plomin’s book on this work here.) But that research must continue in her absence, as Harris has passed away at the age of 80. R.I.P.