Could spanking make a child less intelligent than kids who aren't?

A new study conducted by the University of New Hampshire seems to indicate this is the case. CBS News medical correspondent Dr. Jennifer Ashton explained researchers found that spanking is associated with a lower IQ.

The study will be presented Friday at the Institute on Violence, Abuse and Trauma (IVAT), an international resource and training center at Alliant International University, in San Diego. About 1500 children, Ashton explained, were studied in two different age groups.

The researchers, she said, followed the children over four years, and then rechecked their IQs. "Now, they all got a little bit smarter with age as we would expect with children," Ashton said. "However, those who were spanked had a slightly lower IQ than those who were not -- across both age groups."

Among children ages 2 to 4, there was a five point difference between children who were spanked and those that weren't. And among children from 5 to 9 years old, there was a 2.8 point difference between the two groups. Also, the study controlled socioeconomic factors, Ashton said, such as the educational level of parents and income. However, Ashton pointed out, the study found this was just an association -- not a cause-and-effect finding.

"I don't think it's going to keep anyone out of college," Ashton said. "But, again, the more we learn about the impact of things like spanking, the more things like this will be researched."