The BBC Radio 4 program, More or Less, is a show about statistics, how they are used and abused in reporting the news. Among other regular messages, the presenters spend a lot of time explaining that correlation is not causation, which of course is something we like to hear, since we say it a lot on MT, too (e.g., here).
show, they decided to test science journalists in Britain, to see whether they'd bite on a correlation/causation story they cooked up, or whether they were by now savvy enough not to. The numbers were true, but the mathematician on the show tried to sell the idea that one caused the other, hoping it would warrant a spot on the news.
This guy's story was that there's an extremely strong correlation between the number of mobile phone towers in a given location and number of births. In fact, each tower is correlated with 17.4 births, to be precise. A small village with only 1 tower will have very few births, and a city with a lot of towers will have many more. Well, no one bit. Or rather, one media outlet bit on the story, Radio Wales, who wanted to talk with him about the problem of confusing correlation and causation. Apparently it was pretty obvious.
At first look, though, the mathematician assumed it would appear that the number of towers causes an increase in births. But in fact, of course, both the number of towers and the number of births are a consequence of population size. They are confounded by population size, an unmeasured variable that affects both observed variables. And, regular readers know that the issue of confounding is another frequent feature of MT.
The More or Less presenter is hoping that the fact that this story had basically no takers means that British science journalists are beginning to get the correlation-doesn't-equal-causation message, though as the mathematician pointed out, a recent story about mobile phone use causing bad behavior at school suggests otherwise. And, a glance at the BBC science or health pages is an almost daily confirmation that the problem persists, something we also point out on an as-needed basis.
But that's not really what interested us about this story. What interested us was what happened next, when the presenter asked the mathematician why making causal links was so appealing to humans, given that they are so often false.
The mathematician answered that it's just our instinct, our brains have developed to recognize patterns and respond to them. He said we think of patterns as causal links because 'we survive better that way.' Our ancestors thought that the movement of the stars causes seasons to change, for example -- and....somehow that allowed them to live longer. Thus, he said, it's hard to overcome our instinct to assign causality.
Translated, what he meant was that we evolved to make sense of patterns by finding causal links between two things. (If true, this certainly isn't unique to humans -- we used to have a dog who was terrified when the wind closed a door. But if a human closed it, that was perfectly fine. She actually did understand causation!)
But, isn't the mathematician making the very same error he cautions against? Because we evolved, and because we can see patterns, one caused the other? This is also something we write a lot about, the idea that because a trait exists, it has an adaptive purpose -- the Just-So approach to anthropology, or genetics. Many things come before many other things, but that doesn't help identify causal principles that connect particular sets of things. And, correlation can be made between variables in many different ways. Most are not known to us, or at least we're usually just guessing about what the truth is.