Much research has found that there are IQ differences based on socioeconomic background of children: poorer children have lower IQs. But it’s possible that these differences may be due to health problems in some groups: if poor kids are more likely to get sick, wouldn’t that have some impact on their mental abilities as well?
A new study tries to control for that problem by identifying extremely healthy kids from a variety of socioeconomic backgrounds:
To find a group of healthy children, the NIH researchers screened more than 35,000 youngsters for medical, neurologic and psychiatric disorders, as well as for family histories that point to potential problems or prenatal exposure to toxins. Only 450 of the children met the strict criteria.
These children were tracked for four years while a variety of measures were taken, including IQ tests. The press release offers more details:
Income predicted IQ and academic achievement. Lower income was associated with lower IQ scores (mean IQs were 105, 110, and 115 for low-, middle- and high-income children respectively). Lower-income children were more likely to be excluded from the study because of medical or developmental conditions; the healthy low-income children who qualified performed, on average, better than previously reported population averages. “We were pleasantly surprised by how well the lower-income children did when we focused on those who were healthy,” says Waber. Although income did not predict performance on basic cognitive tasks, such as memory or reading individual words, lower-income children did score lower on tests like reading comprehension and calculation. The authors suggest that such tasks, which require more reasoning and integration of cognitive abilities, are more vulnerable to the effects of poverty-related factors than are more basic skills.
So healthy children score considerably above the mean in IQ tests, and the gap between richer and poorer kids diminishes when health is equal. This suggests that simply improving health care can do a lot to help low-income kids perform better in school. The other differences in IQ also appear to be related to factors that educators can address.
In short, these results support the notion that low IQ is largely a social and health problem, not a predetermined genetic handicap. That said, since the researchers also screened for “family histories” that could be a problem, this might indicate that genetics still play a role. I’d be interested to know what portion of children were excluded from the study for this reason.