Breast Milk or Social Interaction?

Whether the boost in IQ is due to the breast milk itself — such as healthy fatty acids or other substances — or the physical and social interaction that is part and parcel of breastfeeding is unknown, Kramer and others say.

"A mother who breastfeeds is likely to spend more time with her child," he says, as well as read to them later and do other activities. "The amount of time, the closeness, the way she interacts with the kids, undoubtedly differs between breastfeeding and non-breastfeeding mothers."

The bulk of studies on the topic, he adds, have shown a positive link. One notable exception: a study published in 2006 in the British Medical Journal concluded that breastfeeding has "little or no effect on intelligence in children." The study involved more than 5,400 children.