Does traffic congestion make men beat up their wives?

Max Burton-Chellew writes:

I thought this latest paper & news story might be worthy of your blog? I’m no stats expert, far from it, but this paper raised some alarms for me. If the paper is fine then sorry for wasting your time, if it’s terrible then sorry for ruining your day!

Why alarms – well for the usual 1-2-3 of: p-hacking a ‘rich’ data set > inferring an unsubstantiated causal process for a complex human behaviour > giving big policy advice. Of course the authors tend to write this process in reverse.

I think the real richness is the multitude of psychological processes that are inferred for their full interpretation (traffic delays cause domestic violence but not other violence, and more for short commutes than long ones because long ones are less ‘surprised’ by delays etc).

This paragraph is perhaps most illuminating of the post-hoc interpretative approach used:

Next, we examine heterogeneity in the effect of traffic on crime by dividing zip codes along three dimensions: crime, income and distance to downtown. In each specification we subset zip codes in the sample by being either above or below the sample median for each variable. Crime and income are correlated, but there are zip codes that are high crime and high income. Table 4 shows that traffic increases domestic violence in predominantly high-crime and low-income zip codes. We also find that most of the effect appears to come from zip codes that are closer to downtown, which may arise for two reasons. First, households living closer to downtown are more likely to work downtown, and therefore we are assigning them the appropriate traffic conditions. Secondly, a traffic shock for a household with a very long commute may be a smaller proportion of their total commute and a traffic shock might be more expected.

My reply: It’s always good to hear from a zoologist! I’m not so good with animals myself. Also I agree with on you this paper, at least from a quick look. It’s not hard for people to sift through data to find patterns consistent with their stories of the world. Or, to put it another way, maybe traffic congestion does make (some) men beat up their wives, and maybe it makes other men less likely to do this—but this sort of data analysis won’t tell us much about it. As usual, I recommend studying this multiverse of possible interactions using a multilevel model, in which case I’m guessing the results won’t look so clean any more.

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