The new issue of *Psychological Science* includes an article: “Known Risk Factors for Violence Predict 12-Month-Old Infants’ Aggressiveness With Peers.” The authors are Dale F. Hay, Lisa Mundy, Siwan Roberts, Raffaella Carta, Cerith S. Waters, Oliver Perra, Roland Jones, Ian Jones, Ian Goodyear, Gordon Harold, Anita Thapar, and Stephanie van Goozen.

Here are some interesting extracts

“Observational studies of early peer interaction have similarly shown that the use of physical aggression is fairly rare in young children, but that meaningful individual differences are already present by age 3. Infants’ early interactions with peers predict later behavioral problems
Prospective longitudinal studies have identified a number of maternal risk factors associated with high levels of aggression. These risk factors include social class, level of education, and early entry into parenthood; smoking during pregnancy; and stress, anxiety, or depression during pregnancy.

“The infants’ observed aggressiveness was significantly correlated with mothers’ mood disorder during pregnancy and with mothers’ history of conduct problems.

“Our study demonstrated that systematic individual differences in aggressiveness are present by infants’ first birthday. Key risk factors for adolescent violence found in an earlier longitudinal study predicted infants’ observed use of force against peers as well as parents’ reports of infants’ anger and aggression. The precise mechanisms underlying these effects have yet to be identified; parents convey risk through processes of genetic as well as social transmission, and the mother’s mental state in pregnancy”