Humans 0 Rats 1

So why did do many people have trouble working out such a seemingly simple problem? (See previous post). It appears that "our brains are just not wired to do probability very well."

Researchers did an experiment called 'probability guessing'. Subjects were shown a series of cards or lights which can be one of two colours, say red and green. Things are arranged so that the colours appeared with different probabilities, but otherwise with no pattern. For example, red might occur twice as often as green.(Think here perhaps of the over/under 2.5 goals market in football). The task of the subject, after watching for a while, is to predict whether each new member of a sequence will be red or green.

There are two basic approaches. One is to always guess the colour that you notice occurs more frequently. The other is to match your proportion of red and green guesses to the proportion of red and green you have observed in the past. Rats and other non-human animals favour the first approach whereas humans usually adapt the second strategy, trying to deduce a pattern.

Thus humans are outperformed by rats!

To humans, random events often look like non-random events. Sound familiar?