Wednesday, 7 January 2015

A smackdown for the APA on smacking

"Spare the rod", says the Economist magazine, with the subtitle "spanking makes your children stupid". An American Psychological Association task force has reported that corporal punishment goes together with anxiety, depression and behavioural problems.

Six of the best for the Economist, and a sound flogging for the APA, for committing the fundamental statistical sin: confusing correlation with causation.

Sure, corporal punishment goes together with behavioural problems. But there are several ways to interpret that. Maybe corporal punishment causes long run behavioural problems: i.e., if as a parent you decide to use corporal punishment, you make your children's behaviour worse in the long run. But it is also possible that people who use corporal punishment may be less smart, happy, liberal, urban, educated and/or wealthy than those who talk to little Tim about moral values; and that such people have more anxious, depressed, or naughty children, irrespective of how they punish. And isn't it also possible – nay, likely – that children with behavioural problems induce their parents to smack them more?

A dissenting member of the task force made some of these points:
 In the few studies that have compared spanking with other forms of punishment, such as restriction of privileges, grounding and time-outs, all the punitive measures examined resulted in similarly negative outcomes in children....  Scientific American
And a recent meta-review of the evidence [gated content] says:
Concerns with [these analyses] include:
1) Conflation of spanking with more severe forms of corporal punishment...
2) The temporal order of spanking and negative outcomes is not well documented. From cross-sectional correlational studies, it is not possible to determine whether spanking and CP [Corporal Punishment] lead to negative outcomes, or whether children with greater problem behaviors are more likely to be spanked....
3) Controlling third variables... effect sizes based on bivariate correlations run the risk of inflating effect size estimate due to failure to control for other relevant variables.
4) Overreliance on retrospective recall... Retrospective reports of past CP may ultimately say more about the respondent's current psychological status rather than accurate memories of disciplinary acts, which took place years or decades earlier....
It is surprising that such an important topic has been little studied using longitudinal methods, to figure out which came first, the spanking or the naughtiness. But even that would not deal with point (3). Correlation plus being earlier in time is still not causality (e.g. taking one's umbrella to work does not cause rain).

This is a classic case where nothing but a proper experiment will do; but random assignment is very hard to do ethically. "I'm going to give you [flips coin] 20 strokes of the birch!" One approach might be similar to that used by economists studying divorce: look at whether child outcomes are improved in states which ban corporal punishment. This would answer a useful policy question, especially regarding corporal punishment in schools. But the most important "policy" audience here is the parent who wants to know how to discipline his or her children. Perhaps an encouragement design, in which 50% of a group of parents who use corporal punishment are encouraged to give it up, would help.

Meanwhile, there is just very little evidence to go on.

I read my mother's diary from when I was one year old. In one place she writes of getting angry and smacking me: "something (the Devil, I suppose) made me..." My mother smacked me very rarely, that I can remember - perhaps on one or two occasions. Still, her words made me think how one-sided the power relationships are between parent and child. I hope I never feel I have to spank my children.

At the same time, this is a disciplinary method that has been used by parents throughout human history. The idea that it is wrong is very, very recent. Sometimes, traditional ways of doing things have advantages which scientists take a long time to discover (sleeping without a light on, turning the radiator down). Experts should be wary of issuing broad recommendations to the world's parents – especially on such a thin and inadequate evidence base.

(Here is the other point of view.)