When we gamble, something odd and seemingly irrational happens.
It's called the 'hot hand' fallacy – a belief that your luck comes in streaks – and it can lose you a lot of money. Win on roulette and your chances of winning again aren't more or less – they stay exactly the same. But something in human psychology resists this fact, and people often place money on the premise that streaks of luck will continue – the so called 'hot hand'.
The opposite superstition is to bet that a streak has to end, in the false belief that independent events of chance must somehow even out. This is known as the gambler's fallacy, and achieved notoriety at the Casino de Monte-Carlo on 18 August 1913. The ball fell on black 26 times in a row, and as the streak lengthened gamblers lost millions betting on red, believing that the chances changed with the length of the run of blacks.
Why do people act this way time and time again? We can discover intriguing insights, it seems, by recruiting monkeys and getting them to gamble too. If these animals make dumb choices like us, perhaps it could tell us more about ourselves.