October 14, 2009. Retrieved online October 23, 2009 from CARL BIALIK, The Wall Street Journal
Studies Aim to Settle the Longstanding Debate Over the Disciplinary Practice’s Effects, but Statistical Shortcomings Persist
Three recent, widely reported studies on spanking children claimed to show that the disciplinary practice impairs cognitive development in children. Together, they held out the promise of providing the latest, definitive word on a passionate debate.
Yet the three aren’t likely to resolve anything. Many statisticians say they find in them less a firm conclusion than further proof of the difficulty of measuring spanking’s impact.
Statistical analysis of spanking’s effects on cognition are clouded by many complicating factors. Effects can be attributed to the wrong cause, statisticians say; rather than spanking causing problems in children, it is possible that their existing cognitive problems can make spanking more likely. Moreover, any effects of spanking are difficult to measure and probably small. And unlike, say, a study on prescription drugs that removes a misleading placebo effect, no ethical study can assign some children to be spanked. Instead, parents must be trusted to remember and share their disciplinary practices.
….Daniel Mundfrom, a statistician at New Mexico State University in Las Cruces, says that even without accounting for other factors, spanking at age 1 explained less than 1% of the variation in cognitive ability at age 3. In other words, maybe spanking does lower intelligence, but not by much.
…Prof. Straus concedes that the methodology was flawed and that spanking may not account for the differences in average national IQs. He says he presented the data on national IQ in part because it corroborated his other study. “The questionable statistics are so consistent with the statistics in the other paper,” he says, adding that his second study can provide “a field day writing about questionable statistics.”
Some statisticians agree. For one thing, the results are skewed by a relatively small number of countries with high rates of spanking and especially low average IQs, particularly Tanzania and South Africa — where about a third of university students reported being spanked a lot before age 12, and where average IQ rates stood at 72. Excluding these countries, “the line would be much closer to flat, indicating little or no relationship,” says Dr. Mundfrom.
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