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Gamblers are born and not made, according to a Californian study that claims strategic betting behaviour is biological.

The study found that gambling decisions in a simple competitive game were influenced by specific dopamine-regulating genes in a person's brain.

Dopamine is a neurotransmitter - a chemical released by brain cells to signal other brain cells - that is a key part of the brain's reward and pleasure-seeking system.

Gamblers are born and not made, according to a Californian study that claims strategic betting behaviour is biological. The study found that gambling decisions in a simple competitive game were influenced by specific dopamine-regulating genes in a person's brain

It is also the major chemical in the body blamed for an individual's' proclivity to gamble.

Previous studies have shown that when people engage in competitive social interactions, such as betting games, they call upon two areas of the brain: the medial prefrontal cortex, which is the executive part of the brain, and the striatum, which deals with motivation.

'What is really interesting about these areas is that both are innervated by neurons that use dopamine,' said Dr Ming Hsu, an assistant professor of marketing in University of California Berkeley's Haas School of Business.

Dr Hsu wanted to determine which genes involved in regulating dopamine concentrations in these brain areas were associated with gambling behaviour.

They enlisted a group of 217 undergraduates at the National University of Singapore, all of whom had had their genomes scanned for some 700,000 genetic variants.

The researchers focused on only 143 variants within 12 genes involved in regulating dopamine.

Some of the 12 are primarily involved in regulating dopamine in the prefrontal cortex, while others primarily regulate dopamine in the striatum.

The competition was a game called patent race, commonly used by scientists to study social interactions. It involves one person betting, via computer, with an anonymous opponent.

'We know from brain imaging studies that when people compete against one another, they actually engage in two distinct types of learning processes,' said student Eric Set, who was also involved in the study.

Previous studies have shown that when people engage in competitive social interactions, such as betting games, they call upon two areas of the brain: the medial prefrontal cortex (shown here in pink), which is the executive part of the brain, and the striatum (shown by the light blue dot), which deals with motivation

Brain scans show high activity in the medial prefrontal cortex (top) and striatum (bottom) while playing a competitive game

'One type involves learning purely from the consequences of your own actions, called reinforcement learning.

'The other is a bit more sophisticated, called belief learning, where people try to make a mental model of the other players, in order to anticipate and respond to their actions.'

Using a mathematical model of brain function during competitive gambling, the researchers matched up performance in reinforcement learning and belief learning with different variants or mutations of the 12 dopamine-related genes, and discovered a distinct difference.

They found that differences in belief learning – the degree to which players were able to anticipate and respond to the actions of others – was associated with variation in three genes which primarily affect dopamine functioning in the medial prefrontal cortex.

In contrast, differences in trial-and-error reinforcement learning – how quickly they forget past experiences and how quickly they change strategy – was associated with variation in two genes that primarily affect striatal dopamine.

Dr Hsu said that the findings correlate well with previous brain studies showing that the prefrontal cortex is involved in belief learning, while the striatum is involved in reinforcement learning.

'We were surprised by the degree of overlap, but it hints at the power of studying the neural and genetic levels under a single mathematical framework, which is only beginning in this area,' he said.