The gambler's fallacy explained? Misguided belief in the big win just around the corner could be down to brain activity


Science Editor

Gambling addicts are likely to have developed a different pattern of brain activity than non-gamblers which gives them a misguided belief that they can always beat the odds in a game of chance, scientists have said.

A study has identified a region of the brain that appears to play a critical role in supporting the distorted thinking which makes people more likely to gamble because they mistakenly think they have a better-than-average chance of winning.

The researchers found that when this brain region – called the insula – is damaged as a result of brain injury, people become immune to these distortions, such as the classic gambler’s fallacy that a run of “heads” means that a “tails” is now more likely, when in fact the 50:50 odds of “heads” or “tails” have not changed.

The findings support the idea that gambling addiction has a neurological basis and so could be treated with either drugs that target certain regions of the brain, or psychological counselling that aims to counter the distortions that result in compulsive gambling, scientists said.

“Based on these results, we believe that the insula could be hyperactive in problem gamblers, making them more susceptible to these errors of thinking,” said Luke Clark of Cambridge University, who led the study published in the journal Proceedings of the National Academy of Sciences.

“Future treatments for gambling addiction could seek to reduce this hyperactivity, either by drugs or by psychological techniques like mindfulness therapies… The results give us new avenues to explore for the treatment of gambling addiction,” Dr Clark said.

The study was based on psychological tests carried out on a small group of patients in the United States with well defined injuries to certain regions of the brain, notably the ventromedial prefrontal cortex, the amygdala and the insula, he said.

The subjects were asked to assess their chances of winning after playing a pair of computer games designed to simulate two kinds of distorted thinking that are known to stimulate a person’s appetite for gambling.

One was the “near miss” result, exemplified by when a slot machine comes very close – but just failing – to align two winning gold bars in the winning row, which supports the distorted idea that a gambler is getting better through some kind of skill and so is more likely to win the next time.

The other is the classic “gambler’s fallacy”, when for instance a spinning roulette wheel falls repeatedly on the red rather than the black, making someone think wrongly that a black is now more likely, when in fact the 50:50 odds of either a black or red have not changed.

The brain-damaged patients, except those with damaged insula regions, as well as all the healthy “control” subjects, showed a greater desire to continue gambling when subjected to the near-miss outcome and the gambler’s fallacy. The absence of an effect in insula-damaged patients pointed to this part of the brain playing a critical role in fuelling the desire to gamble, Dr Clark said.

“The insula is tucked away in a cleft in the side of the brain and its role is quite mysterious although we know that it’s important for emotion and pain,” Dr Clark said.

“We also know that gambling is a visceral activity. It results in an increase in heart rate, a rise in cortisol [stress hormone] levels and sweating. Gambling causes a lot of physiological changes in the body,” he said.

“The logic of the findings is that the damage to the insula in those patients we looked at reduced these distortions in thinking that normally increase the desire to gamble.

“The next stage of the research is to see whether people who are heavy gamblers show differences in the activity of this part of the brain. We have a major Medical Research Council grant to look at problem gamblers using brain scanners,” he added.

About one in four people in the UK say they have gambled at some time, and about half play games such as the National Lottery. However, gambling becomes obsessive in between 1 per cent and five per cent of players, leading to associated problems such as debt, family breakdowns and mental health problems such as depression.

What is the Gambler's Fallacy?

In 1913, the most famous instance of the Gambler’s Fallacy took place at the Monte Carlo Casino. The ball fell on the black of the roulette wheel 26 times in a row and gamblers lost millions betting against the black, thinking mistakenly that red was more likely because of some imbalance in the wheel that had to be corrected.

Professor David Hand, author of The Improbability Principle, explains that it is the same fallacy that leads people to believe that when tossing a coin a “tails” is more likely than a “heads” after a long series of heads, when in fact the odds are the same as they always were – 50:50.

“Observing a preponderance of heads among the first 10 tosses, many people expect to see this counterbalanced by a preponderance of tails in later tosses. But that’s now what happens. This misunderstanding is so widespread it has a name: the Gambler’s Fallacy,” Professor Hand writes.

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