IQ is in the genes

How smart you are doesn’t depend on how your parents raised you, a new study concludes.

Their reading to you, talking with you at the dinner table and taking an active interest in your life could make you happy. And that’s important. But it won’t make you smarter, says Kevin Beaver.

As a criminologist,he studies the causes of crime and ways to prevent it. Beaver works at Florida State University in Tallahassee. His research team wanted to know if different parenting styles influenced a child’s intelligence. After all, Beaver notes, “intelligence has been linked to crime.”

Previous research has suggested different types of parenting could affect a child’s IQ. Short for intelligence quotient, IQ is a score that measures human intelligence.

But those earlier data hadn’t separated out the effect of genetics on IQ. Beaver’s team wanted to know: Are children’s IQ scores really affected by how their parents raised them? Or are those scores just a reflection of what genes a child inherited?

To find out, the team pored over information from a study of more than 15,000 U.S. middle- and high-school students. It’s called the National Longitudinal Study of Adolescent Health.

Starting in the 1994-to-1995 school year, researchers had asked students a series of questions. For instance: How warm and loving are your parents? How much do you talk with them? How close do you feel to your parents? How much do you think they care about you?

Students also were given a list of 10 activities. Then the questionnaire asked how many of those activities students had done with their parents in the previous week. Did they play sports together? Go shopping? Talk with each other over dinner? Watch a movie together?

Students also answered questions about how permissive their parents were. For example, did their parents let them choose their own friends, choose what to watch on TV or choose for themselves when to go to bed?

The researchers then gave the students a test to gauge their IQ. Called a Picture Vocabulary Test, it asked the students to link words and images. Scores on this test have been linked repeatedly to IQ. Later in life, between the ages of 18 and 26, these people were tested again.

Beaver’s group was especially interested in results from a group of about 220 students who had been adopted. The parents who raised them had not passed on any genes to them. So if there was a link between the students’ IQs and the way their parents raised them, the researchers should see it most clearly in the adopted students’ scores.

But no such link emerged. Whether students reported their parents cared about them and did things with them — or reported that they did not — it had no impact on the their IQ. This means a person’s IQ is largely the result of the genes we inherit from our biological parents.

What does Beaver make of the new findings?

We all have strengths and weaknesses, he says. That means some of us will have to work harder than others to do well. And in some cases, other people will always be better than us at certain things.

“The key is to find what you are good at and what you enjoy.” Then, he says, “Work your hardest to become the best you can be.”

J.C. Barnes is a criminologist who studies how genetics and the environment affect crime. He works at the University of Cincinnati in Ohio. He agrees that the new study shows parents’ behavior does not affect a child’s IQ. Still, he says, it’s important that all parents provide a nurturing environment for their children. 

Parents who do this “give their child the best chance to succeed — not because they improve the child’s IQ, but because they allow the child to develop into a healthy individual,” he says.

Power words

adolescent  A person at a transitional stage of physical and psychological development — one that begins at the onset of puberty, typically between the ages of 11 and 13, and ends with adulthood.

criminologist  Someone who studies criminal behaviors, their rates among different segments of the population, factors that underlie crime, and ways to limit crime.

gene  (adj. genetic) A segment of DNA that codes, or holds instructions, for producing a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.

IQ  Short for intelligence quotient. Through standardized tests, schools and others measure IQ. This score should not change much, if at all, throughout a healthy person’s lifetime. IQ does not measure what someone knows or has learned. Rather it measures one’s capacity to learn, reason and understand information. That information can be delivered in different ways, such as through written words, or as symbols or numbers. Some aspects of the test measure an individual’s ability to learn by asking someone to recall information presented minutes earlier or in different places over a brief span on a computer screen.

longitudinal  (in research) A research project that collects data over a long time; or data representing a long period.