LONDON - Why do people gamble if they know that the house always wins? Researchers argue that near-misses, where the gambler narrowly misses out on the jackpot, may provide part of the answer.

Although the gambler loses the bet on a near-miss, where the slot machine reel stops one position from the ‘payline’, researchers found that near-miss outcomes make people want to carry on gambling and caused brain activity in areas that normally process winning money.

Luke Clark of the University of Cambridge, who led the study, said: ‘Gamblers often interpret near-misses as special events, which encourage them to continue to gamble. Our findings show that the brain responds to near-misses as if a win has been delivered, even though the result is technically a loss.’

The study scanned the brains of 15 people while they gambled on a computerised slot machine that delivered occasional 50 pence wins. These wins caused responses in brain areas that are known to process natural rewards like chocolate, and also drugs linked with abuse.

The researchers showed that near-misses (for example, two cherries and an orange but the not the three cherries necessary for a win) also elicited activity in this brain reward system.

In a second experiment performed outside the scanner, volunteers rated the near-miss events as unpleasant but simultaneously rated their desire to continue the game as higher after a near-miss.

Previous research has shown that gamblers play slot machines with near-misses for longer than machines rigged with no near-misses, said a Cambridge release.

The research found brain activity to near-misses in the striatum and insula cortex of the brain. These areas are thought to be involved in drug addiction, and receive input from the brain chemical dopamine (a neurotransmitter which plays a role in ‘reward’).

Gambling is a widespread form of entertainment in Britain, but some individuals become problem (or ‘compulsive’) gamblers who lose control over their gambling. The symptoms of problem gambling (such as betting larger sums of money over time) are similar to the symptoms of drug addiction, but it is not well understood exactly how behaviours (like gambling) can become addictive.

These findings were published in Neuron.