According to a study that will be printed in the September issue of Psychological Science, breast-feeding moms are more aggressive than moms who use formula. You may be wondering why a study about breast feeding moms might matter to you, and the reason it does is because of what researchers used to test these aggression levels. The researchers' hypothesis was that mothers display a higher level of aggressiveness while breast feeding. This theory is rooted in previous research in non-human mammals that shows that lactation seems to trigger heightened defensive aggression because it apparently decreases an animal's fear response.
To test this theory researchers found 18 mothers who were nursing their children, 17 who were using formula, and 20 women who did not have kids. All of the participants were asked to play a video game against a research assistant who pretended to be an overly aggressive and competitive player. When a participant won a round of the competition, she was allowed to press a button that delivered a "punitive sound burst" to their opponent.
When all was said and done, researchers found that the breast-feeding mothers inflicted the loudest and longest punitive sound bursts on the research assistant than the other two groups. Mothers who breast-fed their infants were almost twice as aggressive as formula-feeding women and non-mothers, according to researchers. Formula-using moms and non-mothers were equal in their levels of aggression – which wasn't all that high, apparently. Oddly enough, researchers also found that while breast-feeding moms were highly aggressive as they played and won their compeititos, their blood pressure remained normal.
"Breast-feeding mothers aren't going to go out and get into bar fights," said UCLA's Dr. Jennifer Hahn-Holebrook, lead author of the study. "But if someone is threatening them or their infant, our research suggests they may be more likely to defend themselves in an aggressive manner."
The Hahn-Holebrook research, "Maternal Defense: Breast Feeding Increases Aggression by Reducing Stress" can be found in the September issue of Psychological Science. More details can be found here.