a Coccyx in the Brain

You might not realize it, but your brain is running some pretty wonky legacy code. Stuff that worked fine back in the day, but is not very well suited for the challenges of modern life. Let me give you an example.

Leonard Mlodinow writes in The Drunkard’s Walk:

Which is greater: the number of six-letter English words having n as their fifth letter or the number of six-letter English words ending in ing? Most people choose the group of words ending in ing. Why? Because words ending in ing are easier to think of than generic six-letter words having n as their fifth letter.

If you have no difficulty coming up with six-letter English words that have an n as their fifth letter, then you’ve probably been playing too much Words with Friends¹ (I am certainly guilty as charged on that count). Anyway, Mlodinow continues:

But you don’t have to survey the Oxford English Dictionary-or even know how to count-to prove that guess wrong: the group of six-letter words having n as their fifth letter includes all six-letter words ending in ing.

Just like the “Linda is a bank teller” example, one answer encompasses the whole of the other answer.

[Note that Mlodinow implicitly (and correctly) assumes that there exist six-letter English words that have an n as their fifth letter but do not end in ing. Otherwise the two groups would have been equal in size.]

Mlodinow explains why we guessed wrong:

Psychologists call that type of mistake the availability bias because in reconstructing the past, we give unwarranted importance to memories that are most vivid and hence most available for retrieval.

In other words: if it’s easy to think of an example, we assume it’s pretty probable.

Good approximation heuristic for a caveman, maybe not so great for modern man. A coccyx in the brain.

In his book The Science of Fear author Daniel Gardner talks about this availability bias (he calls it the ‘example rule’ and Kahneman and Tversky called it the ‘availability heuristic’, but they all mean the same thing) in the context of (perceived) security.

But car crashed aren’t like terrorist hijackings. They aren’t covered live on CNN. They aren’t discussed endlessly by pundits. They don’t inpsire Hollywood movies and television shows. They aren’t fodder for campaigning politicians.

As a consequence of all this public attention, we have no trouble at all thinking of examples of terrorism. Conversely, we have more difficulty thinking of examples of car crashes. Our prehistoric wetware falsely intuits that the former is more likely than the latter; even when we know this to be untrue.

Caveman fears ending with a bang more than the end of the road, because bangs make better stories.

I think it’s about time for a patch. Caveman needs an upgrade. Until then, please be wary of the bugs in your brain.

1. Just so you know, the word ‘coccyx’ is worth a whopping 4+1+4+4+3+8 = 24 points (excluding bonuses) in Words with Friends. However, as there are only two c’s available in each game, you would need both c’s and a joker (or two jokers and a c) in order to be able to play it for twenty points (sixteen with double jokers). ↩