Almost doesn’t count when it comes to slot machines, but our brains like to imagine it does. A study into brain wave activity by researches at the University of Exeter, in England, and Swansea University, in Wales, has found that the brains of gamblers responded nearly as enthusiastically to almost winning as when the machines actually struck the jackpot.

"Our findings show for the first time that gamblers have an exaggerated response to almost winning in brain regions related to reward processing,” says University of Exeter psychologist Natalia Lawrence, one of the authors of the study. “They may be more affected by and perhaps more motivated to keep gambling after a near miss.”

This discovery might help identify those vulnerable to gambling addiction and also be a way to assess the effectiveness of anti-gambling therapy. (Watch: Portable Scanners "Read" Brains on the Go.)

The study monitored the electrical activity in the brains of a cross section of male gamblers, both with and without gambling problems, while they played on slot machines that had win, loss, and near-win outcomes. The results showed that among hard-core gamblers electrical activity in what researchers call the theta frequency—the frequency most associated with winning and losing outcomes—was nearly as high when the slot machine almost hit the jackpot as it did when the jackpot came up. Lawrence spoke with National Geographic about the study.

Why did you test only male gamblers?

Pathological gambling tends to be higher in males than females, so we recruited just males for this reason. There are also several brain imaging studies showing that males and females process some rewards differently. For example, males appear to be more sensitive to monetary rewards whereas females may be more sensitive to social and food rewards.

Was there any noticeable difference in brain waves between winning and almost winning?

In all of the brain regions we examined, brain waves were on average highest for winning, lower for almost winning, and lowest of all for losing. This parallels what we see in people's own ratings of "closeness to a win." They obviously rate wins highly, followed by almost wins, and then losses. Therefore, even though people lose on almost win trials, they rate these outcomes as "closer to a win" than losses. The brain theta oscillations echo that pattern.

Was that finding true across the board?

In one brain region that is involved in processing rewards—the right orbitofrontal cortex—gamblers showed similar increases in theta oscillations to winning and almost winning, whereas nongamblers showed a clear difference between winning and almost winning.

What exactly are theta brain waves? And how do you know they are linked with gambling activity?

Theta brain waves are neural oscillations that are thought to play a role in memory formation and navigation in the hippocampus of animals, and are known to interact with other high-frequency brain rhythms to accomplish these goals. However, there is relatively little known about their particular significance in the human brain. Whilst there is no current complete theory regarding the role of theta waves in human neurophysiological processes, here we propose that they at least in part reflect a semi-automatic process of evaluating win and loss outcome[s].

Was the increased activity in theta waves after a near win (or near miss) found only in people with gambling troubles or was it observable in the control group as well?

Both those with and without a gambling history showed increased activity to almost wins compared to losses, but only gamblers showed similar theta responses to wins and almost wins [in the right orbitofrontal cortex].

What is your next step with this research?