Dr. Natalia Lawrence of the University of Exeter and Dr. Simon Dymond at Swansea University said they pinpointed the changes in the brain that lead gamblers to react in the same way to near-misses as they do to winning.
"Our findings show for the first time that gamblers have an exaggerated theta response to almost winning in brain regions related to reward processing, which could contribute to them continuing to gamble despite their losses," Lawrence said in a statement.
"If replicated, these brain activity changes could help us identify those vulnerable to gambling addiction and might be a useful measure of the effectiveness of therapy for gambling related problems."
The researchers studied male gamblers and non-gamblers and exposed them to simulated slot machines presenting win, loss and near-miss outcomes. The study subjects underwent a brain scan using a technique called magnetoencephalography, which measures both the timing and location of brain responses to different gambling outcomes.
It emerged that theta activity increased in response to near-misses relative to other losses in brain regions such as insula and orbitofrontal cortex -- parts of the brain involved with consciousness, emotion, perception, motor control, self-awareness and cognitive functioning -- which are linked to gambling severity.
"Problem gambling is a growing social concern, and the brain and behavioral effects of 'almost winning' are now well documented," Dymond said. "Advances in brain imaging techniques mean we are now able to pinpoint the precise brain regions involved in the near-miss effect and identify how they interact with people's vulnerability to problem gambling."
The study leaders presented the findings in the journal NeuroImage.