The low-frequency trap

I’m sure someone smarter than me has named this phenomenon already, but just in case…

There is a section of the watershed popular psychology book Thinking, Fast and Slow about the availability heuristic.  Loosely, when asked about the frequency of some event, we tend to answer as if we’d been asked how many such events we can remember.  Because events like murders or terror attacks are always fresh in mind, we tend to rate them as frequent, although they are not (the death rate from terror in France is much lower than the famously low murder rate in Japan).  In fact it is their infrequency among other things that makes them memorable, which in turn makes them easier to recall, which makes them seem more frequent than they really are.

The infrequency of an event itself can result in that event seeming frequent.

You actually need very few assumptions to come to the conclusion that your instincts will reliably get questions of frequency very wrong.

One, that unusual things are more likely to be reported, passed on, or simply remembered when observed, and:

Two, that ease of recall is surreptitiously substituted for actual statistical frequency when people are asked “how often does X happen?” or “how common is X?”

The result of these two factors colluding plus the omnipresence of information and news in modern life is that people vastly overestimate the prevalence of airplane crashes, rare diseases, and Olympic medalists from the country whose news they consume.  On a smaller scale, you will judge more prevalent a strange-looking breed of dog you’ve only seen once or twice, a particularly pleasant or unpleasant social encounter you had while visiting a new place, and a bad meal at a restaurant that’s usually good.  Of course the converse, that people will underestimate the frequency of mundane or expected events like deaths from heart disease or days without terror attacks, is true as well, and has some warping effects on the public policy choices of our representatives in government, who are beholden to electorates who suffer from these endemic mental processing bugs or suffer from them themselves.

This and basically all the other chapters of that book leave you with the inescapable impression that trusting your gut is a terrible decision.  Unfortunately it is also a decision that most other people will sympathize with and understand, and is unlikely to lead people to blame you when your illogical choice fails.  The temptation to engage as little of your slow-thinking brain as possible comes from both the uncomfortable mental labor involved as well as from people we have to explain our decisionmaking processes to.

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