My print column this week examines three recent studies tying spanking of children to their impaired cognitive development. One study, co-authored by Lisa J. Berlin, a developmental psychologist at Duke University, found that spanking at age one is linked to lower scores on a cognitive test at age three. Another study, co-authored by Murray Straus, also ties spanking at one age to lower cognitive scores at a later age. And a third study by Straus, presented at a recent conference, ties nations' high rates of spanking to lower average IQs。
Skeptics of such studies note that they often fail to demonstrate that spanking caused the measured effects; perhaps cognitive problems are tied to behavioral problems, which themselves cause spanking. Berlin’s study addressed this by examining whether cognitive development at age two was tied to spanking at age three; it wasn't。
Another common weakness of spanking studies, according to Robert Larzelere, a research methodologist at Oklahoma State University and former colleague of Straus's as a post-doctoral fellow, is that they don’t compare spanking to other forms of punishment. Berlin partially addressed that, by comparing spanking to verbal punishment, which didn’t have the same links to poor cognitive development. Larzelere said his own studies, however, show that all corrective actions -physical and otherwise - have essentially the same effects。
“Spanking researchers have been waiting a long time for a study as high-quality as this one,” Marjorie Gunnoe, a professor of psychology at Calvin College in Grand Rapids, Mich., said。
However, the controversy over spanking isn't likely to be settled over these studies. It is a subject of dispute between the American Academy of Pediatrics and a smaller, splinter group called the American College of Pediatricians that supports spanking in certain instances. “No one likes to spank a child, but for some children it is the only method that will work to gain control of the child’s behavior and ultimately the will,” said Dr. Den Trumbull, vice-president of the group, and a pediatrician in Montgomery, Ala.
Adam Zolotor, an assistant professor of family medicine at the University of North Carolina, Chapel Hill, said that to control for sufficient variables such as genetics would require a complex research effort. “The best way to do this would be to get enough twins that were separated at birth,” he said. “Let's say you need at least 500 twins separated at birth, and probably more. I don’t know if you could find that many.”
Vivian Friedman, a professor and clinical psychologist at the University of Alabama at Birmingham school of medicine also doubts that a research study could ever settle the spanking debate. “The best way to test their hypothesis that spanking lowers IQ would be to...to measure IQ in a child repeatedly over time (maybe every year or two years) while measuring the numbers of spankings administered,” Friedman said. “Even so, it would be hard to rule out other physical and emotional environmental factors for causality。”