Australasian Science: Australia's authority on science since 1938

Knowing When to Fold ‘Em

By Tim Hannan

The discovery that some brain injuries may eliminate the gambler’s fallacy could lead to pharmaceutical treatments for problem gambling.

At first glance, the various forms of gambling appear to be games that require a participant to make decisions based on a reasoned calculation of the probabilities of various outcomes. Yet psychological research has revealed that gamblers typically commit cognitive errors that promote a greater expectation of winning, such as the well-known gambler’s fallacy of expecting that if one of two equally likely outcomes has occurred several times in a row (e.g. a tossed coin landing on heads repeatedly), the other outcome (tails) then becomes more likely.

A novel study has now found that certain focal brain injuries may reduce or eliminate the gambler’s fallacy, suggesting that these types of cognitive errors are related to the activity of a specific region of the frontal lobes.

While gambling has been a popular pastime throughout human history, the social consequences of problem gambling have prompted psychological research into its causes. Several characteristic errors in reasoning have been identified among gamblers, each of which creates an enhanced expectation of winning.

In addition to the systematic misjudgement of random sequences known as the gambler’s fallacy, another error is the near-miss effect, which is the increased expectation of success following an unrewarded outcome that was nevertheless close to the target: “because I nearly won last time, I am more likely to win next time”.

All who engage in gambling appear prone to such misjudgements, but studies have suggested that problem gamblers may be particularly susceptible to these cognitive biases.

Previous attempts to identify the brain regions associated with these cognitive errors have produced mixed results. Cerebral imaging studies of individuals with various disorders of impulse control have suggested the presence of abnormalities in parts of the prefrontal cortex, a region implicated in decision-making and the calculation of risk, as well as in sub­cortical regions involved in emotions, such as the amygdala. Under­activation in these areas has been associated with behavioural addictions such as gambling as well as substance addictions, which has suggested that both types of impulse control dis­orders are mediated by similar brain processes.

This hypothesis has been supported by studies of sufferers’ performance on cognitive tasks that require calculations of risk and reward, with those who have behavioural and substance use disorders preferring smaller immediate monetary rewards rather than larger delayed rewards.

The recent study by Luke Clark and colleagues at the University of Cambridge adopted a novel approach to investigate the neurological basis of the cognitive distortions observed in gamblers. They recruited participants with focal injuries to either the ventromedial prefrontal cortex, the insula or the amygdala, and compared their performance with both healthy individuals and those with lesions in other brain regions.

Each participant played a roulette game, with the researchers observing whether they chose a colour with reduced frequency immediately after a run of that colour outcome. The participants also played a poker machine and were asked to rate their motivation after both near misses and other unsuccessful outcomes.

The results were that the healthy participants and three of the four brain-injured groups evidenced both the gambler’s fallacy on the roulette wheel and the near-miss effect on the poker machine. However, the patients with specific lesions in the insula did not show either error, which suggested that damage to this region had disrupted the tendency to these cognitive distortions.

The research team interpreted these findings to suggest that the insula, a region of the cortex located in the folds of the lateral fissure that separate the frontal lobe from the temporal lobe, may play a critical role in supporting certain types of cognitive distortions. While such biases appear to occur in all human brains, it may be that in problem gamblers the tendency is more exaggerated or more difficult to restrain due to hyperactivity of the insula.

The study has generated new and testable hypotheses about the neuroscientific basis of gambling, and the researchers have speculated that the findings may eventually lead to pharmacological interventions for problem gambling.

Tim Hannan is an Associate Professor of Clinical Psychology at Charles Sturt University, and the President of the Australian Psychological Society.