But I Did Everything Right!

• The gene variant that influences whether children learn from their mistakes. With the misspelled gene, brains have about 30 percent fewer dopamine receptors and less activity in the brain's frontal cortex (the site of higher-order thinking, including monitoring negative feedback) and hippocampus (memory) than do people with the more common form of the gene. In an experiment at the Max Planck Institute for Neurological Research in Germany, people with the misspelling weren't able to avoid choices that they were told over and over were incorrect. Numerous other studies have linked this gene variant to addiction, obesity and compulsive gambling, suggesting that the underlying problem is trouble learning the negative consequences of your actions.

• The DNA variant that affects whether a baby's brain development will be spurred by breast-feeding, which has been reported to confer an extra half-dozen or so IQ points by kindergarten. But not all breast-fed babies are little Einsteins, making their mothers wonder why all the milk-stained blouses didn't seem to boost cognitive development. The reason seems to be that there are two forms of a gene called FADS2. In the 90 percent of babies who carry the "C" form, breast-feeding raises intelligence by an average of nearly seven IQ points, scientists led by Terrie Moffitt and Avshalom Caspi of Duke University reported last year. This version of FADS2 produces an enzyme that helps convert the fatty acids in breast milk into compounds that help signals zip along brain neurons and spur neurons to sprout connections, which underlie intelligence, memory and creativity. The 10 percent of babies who carry the other form of the gene lack the enzyme and therefore derive no cognitive benefit from breast-feeding (though they still get an immune-system boost from it).

• DNA variants can protect children from bad parenting. For instance, most girls who are sexually abused are at higher risk for becoming alcoholics, as well as for developing other mental-health problems. But girls who have a "sluggish" version of the gene called MAOA seem to be vaccinated against this effect, reported scientists led by neurogeneticist David Goldman of the National Institute on Alcohol Abuse and Alcoholism last year. With the active version of MAOA, the brain's hippocampus—which processes emotional experiences and memories—becomes hyperactivated when it remembers something upsetting, such as abuse, and the woman turns to alcohol for solace. With the sluggish version, those memories lose their awful power. Another protective gene insulates children from the effects of an emotionally distant mother, one who is cold and uncaring, who turns away when her child feels the pain of a skinned knee no less than from a crushed dream. That is supposed to make a child more likely to develop "externalizing behavior," acting out in a bid for attention. But children with a certain form of a gene called DRD4, which stands for dopamine-receptor D4, are Teflon-coated, at little to no risk of becoming emotionally insecure as a result of mothers who are emotionally distant, found a 2007 study.

The discoveries questioning the connection between what parents do and how children turn out has not exactly taken the science of child development by storm. That seems to reflect a culture clash within the field. Most researchers who study child development were trained as psychologists, and—to overgeneralize, but only a little—are uncomfortable with or even suspicious of genetics. Geneticists tend to see behavioral research as squishy, not hard science. That produces a body of scientific literature that is remarkably ignorant of genetics. As we reported in this story, we were struck by how clueless so many "experts" in child development were about the new genetics—and how resistant they were to it. Almost all were unaware of the studies showing that genetics acts as a filter between environment and child, letting some influences in and keeping others out. "Even the stuff published in the best journals ignores the underlying genetics," says one leader in the field.

Since companies already offer storefront DNA tests, the day is not far off when parents can determine their child's MAOA or DRD4 status, or the presence of any other variant that influences the effect of parenting. But perhaps it is time to acknowledge that there is only so much influence parents can have. In her best-selling book "I Feel Bad About My Neck," Nora Ephron laments how American society "came to believe in the perfectibility of the child just as it also came to believe in the conflicting theory that virtually everything in human nature was genetic." Both views—that everything is genetic and that parents can transform a child like a lump of clay—are as wrong as wrong can be.

With Jeneen Interlandi and Anna Kuchment in New York and Karen Springen in Chicago

© 2008