Will the coming generations of children be smarter

How intelligent a person is depends on various factors - by no means all of them are known. What is clear is that genes play a role. Most intelligence researchers assume that the degree of heredity is around 50 percent. Whether a person can make use of their innate possibilities then depends on the environment in which they grow up. A team of researchers from the University of Virginia has now proven this again in a study.

For the study, brothers were examined, one of whom grew up with their birth parents while the other was adopted (PNAS, online). The scientists were able to show, among other things, that the level of education of the parents has an influence on the intelligence of the children; but less than expected.

The intelligence researchers examined 436 pairs of brothers who were born in Sweden between 1955 and 1990. In each case one of the boys was adopted by another family as a toddler, the other lived with their birth parents for at least ten years.

As a measure of intelligence, the researchers used IQ, which was determined between the ages of 18 and 20 in the aptitude test for the military. On average, the intelligence quotient of the adopted men was slightly higher than that of the brothers who had lived with their birth parents. It was also fitting that the adoptive parents had, on average, a higher level of education than the birth parents. In one extreme case, the adopted boy's IQ was 7.6 points above that of his brother.

Another extreme example showed that the education of the parents has an influence on the intelligence of the children: The intelligence quotient of a boy who had been adopted by parents whose educational level was significantly below that of the biological parents was 3.8 points lower than that his brother. Despite such correlations, the study also showed that the differences in the educational level of parents and carers alone cannot explain the deviations in the brothers' IQ. The researchers suspect that many other environmental factors also play a role; possibly what the children experienced before they were adopted.