By eliminating all extraneous factors, such as varied birth weight, socioeconomic groupings, mothers’ intellectual capabilities, the researchers were able to accurately test the intelligence of these children, either by recently being tested at ages 7, 9, 11, and 13 years as with the English children or from intelligence tests given to the New Zealand children about thirty years ago.

They found that the FADS2 gene helped to produce a more intelligent child. The gene helps in the break down of fatty acids within human milk. It comes in two forms, where one form is more efficient in breaking down fatty acids. If children carried one or two copies of the more efficient form of the FADS2 gene, then they displayed higher intelligence. However, this higher intelligence was only present if they were also regularly breast-fed during infancy.

In fact, children that contained the more efficient form of the FADS2 gene and were breast-fed in infancy, also had an IQ level that was six or seven points higher than other children.