Children spanked by their parents grow up less clever than those not physically punished, says a new groundbreaking research.
The study by University of New Hampshire professor Murray Straus will be presented Friday, Sept. 25, 2009, at the 14th International Conference on Violence, Abuse and Trauma, in San Diego, Calif.
"All parents want smart children. This research shows that avoiding spanking and correcting misbehavior in other ways can help that happen," Straus says.
"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," the expert added.
traus found that children in the United States who were spanked had lower IQs four years later than those who were not spanked.
To reach the conclusion, Straus and Mallie Paschall, senior research scientist at the Pacific Institute for Research and Evaluation, studied nationally representative samples of 806 children ages 2 to 4, and 704 ages 5 to 9. Both groups were retested four years later.
IQs of children ages 2 to 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 to 9 years old who were not spanked were 2.8 points higher four years later than the IQs of children the same age who were spanked.
"How often parents spanked made a difference. The more spanking the, the slower the development of the child's mental ability. But even small amounts of spanking made a difference," Straus says.
Straus also found a lower national average IQ in nations in which spanking was more prevalent. His analysis indicates the strongest link between corporal punishment and IQ was for those whose parents continued to use corporal punishment even when they were teenagers.
Straus and colleagues in 32 nations used data on corporal punishment experienced by 17,404 university students when they were children.
According to Straus, there are two explanations for the relation of corporal punishment to lower IQ.
First, corporal punishment is extremely stressful and can become a chronic stressor for young children, who typically experience corporal punishment three or more times a week. For many it continues for years. The research found that the stress of corporal punishment shows up as an increase in post-traumatic stress symptoms such as being fearful that terrible things are about to happen and being easily startled. These symptoms are associated with lower IQ.
Second, a higher national level of economic development underlies both fewer parents using corporal punishment and a higher national IQ.