Growing up in a poor family may suppress a child's genetic potential to excel cognitively, a new research has claimed.
The University of Texas study found that half of the gains that wealthier children show on tests of mental ability between 10 months and 2 years of age can be attributed to their genes.
But children from poorer families, who already lag behind their peers by that age, show almost no improvements that are driven by their genetic makeup, found the study.
However, the findings do not suggest that children from wealthier families are genetically superior or smarter. They simply have more opportunities to reach their potential.
These findings go to the heart of the age-old debate about whether "nature" or "nurture" is more important to a child's development, said Elliot Tucker-Drob who led the study.
It found that both "nature" and "nurture" work together and that the right environment can help children begin to reach their genetic potentials at a much earlier age than previously thought, Tucker-Drob noted.
He said: "You can't have environmental contributions to a child's development without genetics. And you can't have genetic contributions without environment. Socioeconomic disadvantages suppress children's genetic potentials."
For their research, the team looked at test results from twins who had taken a version of the Bayley Scales of Infant Development at about 10 months and again at 2 years of age.
The test, used to measure early cognitive ability, asked children to perform such tasks as pulling a string to ring a bell, putting three cubes in a cup and matching pictures.
At 10 months, there was no difference in how the children from different socioeconomic backgrounds performed. But by two years, children from high socioeconomic background scored significantly higher than those from poor 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 that 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 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," said 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.