Environment or genetics? Which plays the most important role in determining the mental ability of children? A recent study suggests that both can be important. Which one is most relevant depends on the economic status of families.
Jonah Lehrer reports in The Wall Street Journal on a paper published in Psychological Science in which scientists studied 750 pairs of American twins who were given a mental ability test at the age of 10 months and again at the age of 2. By looking at the test scores of identical vs. fraternal twins, the researchers could factor out the relative importance of genetics and home environment. The infants came from a wide range of socioeconomic backgrounds, so it was possible to also measure how wealth influenced performance. Key findings included:
- For the 10-month-old babies, the home environment was the key component in every socioeconomic class.
- For the 2-year-olds, the results were very different: 1)The activity of parents mattered greatly in children from poorer households. In fact, the study estimated that the environment accounted for 80% of the variance in mental ability among these toddler from poor homes, while 2)The opposite pattern appeared in 2-year-olds from wealthy households. For these children, genetics primarily determined performance, accounting for 50% of variation in mental ability.
The conclusion seems to be that home environment plays a huge role in determining the mental ability of babies, but the impact of the environment decreases as children grow older in homes with a higher socioeconomic status. These results reflect the developmental inequalities that begin almost immediately in homes, even to the extent of affecting the mental abilities of toddlers.Previous studies have centered on factors such as the vocabulary used in homes, the number of books available to children, and the ratio of encouraging remarks to discouraging words directed toward children as causes for the developmental differences in children from homes in poverty.
Such statistics cause policy-makers to discuss how to best address the inequities that poor children face. Many have long advocated for increased investment in preschool education, but this study suggests that interventions should begin even earlier. Practically every parent, whether rich or poor, deeply desires that his or her child succeed. The challenge facing society is giving those parents in most need the skills to provide their children the environment to support their development.