Long-Term Study Shows Gender and Income Differences Don't Affect Intelligence Much

Does being born rich, male or female make you smarter? Researchers at the National Institutes for Health (NIH) have been studying hundreds of children for eight years to find out just that.

Announcing the initial findings of their ongoing study of healthy brain development in children between birth and young adulthood, researchers at stated that gender differences and income are less significant influences on cognitive function that previously believed. This information was published online May 18 in the Journal of the International Psychological Society.

The data is the first released from the study that began in 1999 and documents the structural development and behavior in children with a healthy brain. According to NIH Director Elias A. Zerhani, MD, "This report - and many others that will follow - provides a comprehensive set of benchmark values that clinicians and scientists studying brain development can reference for many years to come."

Researchers enrolled approximately 450 children in the study; of those, 385 were six years or older. Participants were asked to complete a battery of cognitive tests to quantify their overall I.Q., verbal ability, mental processing speed, spatial ability, memory, fine motor dexterity, psychosocial function, reading and calculation ability as well as other cognitive functions.

Initial results from the pre-adolescent children mirrored previously held beliefs that gender did play a role in cognitive function, although not as much as previously believed. The extended length of the study allowed for a first, then second follow up that showed that by adolescence the gender based cognitive advantages disappeared even though initially boys performed better on perceptual analysis and girls performed better on processing speed and motor dexterity as well as having a slight advantage on verbal learning.

Lower income children were more likely to be excluded from the study because of medical or developmental issues. The children who did qualify from this group performed better than those in previous studies.

The research did, however, show that income level could be used as a predictor of I.Q. and academic achievement as I.Q. rose by five points for each income level: 105, 110, and 115 respectively for low, middle and high incomes. While income did not predict performance on basic cognitive tasks, such as memory or reading individual words, lower-income children did score lower on tests such as reading comprehension and calculation.

The goal of the study is to provide a comprehensive set of guidelines on the development of the brain of a healthy child and connect the study's imaging findings with neurobehavioral abilities. One of the unique aspects of the study is having access to the same population of children over such a long period of time.

FULL TEXT: Select The NIH MRI study of normal brain development: Performance of a population based sample of healthy children aged 6 to 18 years on a neuropsychological battery here.