DURHAM, N.H., Sept. 25 (UPI) -- U.S. children who were spanked had lower IQs four years later than those not spanked, researchers found.
University of New Hampshire Professor Murray Straus, who is presenting the findings Friday at the 14th International Conference on Violence, Abuse and Trauma, in San Diego, called the study "groundbreaking."
"The results of this research have major implications for the well being of children across the globe," Straus said in a statement.
"It is time for psychologists to recognize the need to help parents end the use of corporal punishment and incorporate that objective into their teaching and clinical practice."
Straus and Mallie Paschall, senior research scientist at the Pacific Institute for Research and Evaluation, studied a nationally representative sample of 806 children ages 2-4, and 704 children ages 5-9.
IQs of children ages 2-4 who were not spanked were 5 points higher four years later than the IQs of those who were spanked. The IQs of children ages 5-9 who were not spanked were 2.8 points higher four years later than the IQs of children not spanked.
"How often parents spanked made a difference. The more spanking the, the slower the development of the child's mental ability," Straus said. "But even small amounts of spanking made a difference."
Straus also found a lower national average IQ in nations in which spanking was more prevalent.
