According to research from psychologists at The University of Texas at Austin, growing up poor can suppress a child’s genetic potential to excel cognitively even before the age of two.

While the study found the gains wealthier children show on tests of mental ability between 10 months and 2 years of age can be attributed to their genes, children from poorer families, who already lag behind their peers by that age, show almost no improvements that are driven by their genetic makeup.

However, that doesn’t mean wealthier children are genetically superior to poorer children, it just means they have more opportunities to reach their potential.

These findings go to the heart of the age-old debate over which is more important to a child’s development: “nature” or “nurture.”  They suggest the two work together and that the right environment can help children begin to reach their genetic potentials at a much earlier age than previously thought.

According to Assistant Professor Elliot Tucker-Drob, lead author of the study, socioeconomic disadvantages suppress children’s genetic potentials.

“You can’t have environmental contributions to a child’s development without genetics. And you can’t have genetic contributions without environment,” said Tucker-Drob, who is also a research associate in the university’s Population Research Center.

The study, published in the journal Psychological Science, was co-authored by K. Paige Harden of The University of Texas at Austin, Mijke Rhemtulla of the University of Texas at Austin and the University of British Columbia, and Eric Turkheimer and David Fask of the University of Virginia.

The researchers looked at test results from 750 sets of twins who had taken a version of the Bayley Scales of Infant Development at about 10 months old, and again at about two years of age.

The test, which is widely used to measure early cognitive ability, asks children to perform tasks like pulling a string to ring a bell, putting three cubes in a cup, and matching pictures.

At 10 months old, there was no difference in how the children from different socioeconomic backgrounds performed.

But by two years old, children from high socioeconomic background scored significantly higher than those from low socioeconomic backgrounds.

In general, the two-year-olds from poorer families performed very similarly to one another. That was true among both fraternal and identical twins, suggesting genetic similarity was unrelated to similarities in cognitive ability. Instead, their environments determine their cognitive success.

Among two-year-olds from wealthier families, identical twins (who share identical genetic makeups) performed very similarly to one another. But wealthy fraternal twins were not as similar -- suggesting their different genetic makeups and potentials were already driving their cognitive abilities.

“Our findings suggest that socioeconomic disparities in cognitive development start early,” says Tucker-Drob.

“For children from poorer homes, genetic influences on changes in cognitive ability were close to zero. For children from wealthier homes, genes accounted for about half of the variation in cognitive changes.”

The study notes that wealthier parents are often able to provide better educational resources and spend more time with their children but does not examine what factors, in particular, help their children reach their genetic potentials. Tucker-Drob is planning follow-up studies to examine that question.