Murray Strauss, PhD, Director of the Family Research Laboratory at the University of New Hampshire at Durham, informed Medscape Psychiatry that his 32-nation landmark study on corporal punishment by parents and children''s IQ''s suggests that corporal punishment, in part, may result in a general lowering of children''s IQ''s throughout the world, when the circumstances are the same. He pointed out that the longitudinal part of the study showed that children who had the lowest scores had been spanked were behind the developmental mean of the curve for IQ, while those who have never been spanked were above the same. Strauss indicated that the strongest correlation between corporal punishment and lower IQ occurred in cases where parents continued to engage in corporal punishment, even when the subjects were adolescents.
Elisabeth Gershoff, PhD, Associate Professor in the Department of Human Development and Family Sciences at the University of Texas, Austin, who has herself carried out research studies on the effects of corporal punishment of children by parents, told Medscape Psychiatry that Dr. Strauss observed that there is "an interesting relationship between national incidence of the corporal punishment of children, their experiencing of stress, and their IQ''s," but that it is premature to suggest another causal phenomenon that might explain why corporal punishments lowered IQ''s, in ever-increasing numbers, even at different educational levels. Parents who have achieved higher levels of education are less likely to use corporal punishment; they are more likely to commit themselves to activities like reading to their children and helping them with their homework. The psychological mechanism by which spanking leads to inferior cognitive abilities remains vague.