Tuesday April 8 2014
The small chance of a big win can lure unwary gamblers
“The gambler’s fallacy explained? Misguided belief in the big win just around the corner could be down to brain damage,” The Independent incorrectly reported.
The news is based on a small experimental study that assessed performance in two gambling games in healthy people, and in people with damage to specific regions of the brain.
One of the games was a slot machine game, which assessed motivation to continue playing after a near miss. The other was a roulette game. This game assessed gambler’s fallacy, the belief that past results have an influence on future results (see box). The researchers looked to see whether participants chose a colour (red/blue) after runs of that colour outcome.
In healthy people, compared with “full misses”, near misses increased motivation to continue playing the slot machine game. In the roulette wheel game, healthy people were less likely to choose a colour after a run of the same colour.
However, people with brain damage to the insula (a region of the brain believed to be involved in feelings and emotional responses) had reduced motivation to play the slot machine task following near misses compared with full misses, and did not display classic gambler’s fallacy effect on a roulette wheel game.
Further larger studies are required, but overall the results of this study suggest that the insula region of the brain may play a role in the responses to gambling, as well as playing a role in how we make decisions in different settings.
Where did the story come from?
The study was carried out by researchers from the University of Cambridge and University College London in the UK and the University of Iowa and University of Southern California in the US. It was funded by the UK Medical Research Council and the US National Institute of Neurological Disorders and Stroke, and the National Institute on Drug Abuse.
The study was published in the peer-reviewed journal, Proceedings of the National Academy of Sciences (PNAS).
The news was generally well covered by the media, although it is yet to be determined whether the insula is overactive in people with gambling addiction, as suggested by the Mail Online. The Independent’s initial online headline – that the gambler’s fallacy could be down to “brain damage” – was later updated to more correctly say that the issue could be related to “brain activity”. The print version of the paper ran the more subtle if still slightly awry headline “Feeling lucky? Now scientists can tell gamblers why”.
What kind of research was this?
This was an experimental study that aimed to compare performance in two gambling games in healthy people and in people with injuries in specific regions of the brain. The aim was to see which brain regions could be involved in two gambling distortions: the response to “near-miss” outcomes and the processing of random sequences.
A study such as this is hypothesis generating – that is, it suggests theories as to what parts of the brain may be involved in responses to gambling. However, it does not provide proof that these areas are responsible for problem gambling and further research is needed.
What did the research involve?
The researchers compared people with brain injuries in specific target regions:
- 17 with damage to the ventromedial prefrontal cortex [vmPFC]
- eight with damage to the insula,
- six with damage to the amygdala
They compared these with 16 healthy people, and 13 people with brain injuries that did not affect those specific regions.
Participants were given a computer slot machine and roulette games.
The slot machine game was programmed to deliver near-misses, as well as wins and full-misses. Half the time participants were asked to select a play icon from one of six alternatives, the rest of the time the computer selected a play icon. After the play icon was selected, participants were asked to rate their chances of winning. The participants then received a win or no-win result. After each play, participants were asked how pleased they were with the result and how much they wanted to continue playing the game.
Participants played 90 times on the roulette wheel game. The roulette wheel displayed an equal number of red and blue segments, and before each game the participant had to choose a colour. This game assessed gambler’s fallacy. The gambler’s fallacy is a bias in the processing of randomness, whereby recent consecutive outcomes are considered less likely to repeat, and conversely, outcomes that have not occurred in the recent history are perceived as “due”. The researchers looked to see whether participants chose a colour (red/blue) after runs of that colour outcome.
What were the basic results?
Slot machine game
When participants selected the play icon for themselves, rather than the computer selecting it for them, they rated their chances of winning as higher. The researchers suggest that this is consistent with the illusion of control that leads from personal choice. There was no difference between people with injuries in specific target regions, healthy people and people with other brain injuries.
Participants were happiest with the result when they received a win, although response to a win was significantly reduced in people with injuries in specific target regions compared to people with other brain injuries. How pleased participants were with winning was not affected by whether they or the computer had selected the play icon.
Receiving a win increased motivation to continue. There was no difference between people with injuries in specific target regions, healthy people and people with other brain injuries, and motivation was not significantly affected by whether they or the computer had selected the play icon.
Compared with full misses, near misses also increased motivation to continue playing. However, people with brain injuries in specific target regions had reduced motivation to continue playing following near misses versus “full misses” compared to healthy participants and participants with other brain injuries.
When the people with injuries in specific target regions were divided up, it was found that people with injuries in the insula had reduced motivation to play following a near miss than following a full miss. People with injuries in the vmPFC also had reduced motivation to play following a near miss than following a full miss, but the difference was smaller.
Roulette wheel game
In the roulette wheel game, participants chose each colour less after longer runs of the colour. This effect did not vary between groups.
However, when the people with injuries in specific target regions were divided up, it was found that people with injuries in the insula were more likely to choose a colour after longer runs of the same colour. This was different to people with injuries to the vmPFC and amygdala.
How did the researchers interpret the results?
The researchers conclude that, “our findings indicate that the distorted cognitive processing of near-miss outcomes and event sequences may be ordinarily supported by the recruitment of the insula. Interventions to reduce insula reactivity could show promise in the treatment of disordered gambling.”
This experimental study in a small number of people with different brain injuries and a comparison group of healthy people, has found that people with brain damage to the insula (a region of the brain believed to be involved in feelings and emotional responses) had reduced motivation to play the slot machine task following near misses compared with full misses. These people also did not display classic gambler’s fallacy effect on a roulette wheel game – in that they were not more likely to choose a blue after long runs of red or vice versa.
A study such as this suggests regions of the brain that may be involved in responses to gambling. However, it does not provide proof that any particular part of the brain causes gambling addiction. The study has involved only a small number of people, and comparing game performance in people with and without brain injuries does not reflect the real life scenario of gambling by people with gambling addiction.
This study could be followed up by carrying out brain imaging on people with known gambling problems to see which parts of their brain were active.
Overall, the results of this small study suggest that the insula region of the brain may play a role in responses to gambling, as well as playing a role in how we make decisions in different settings, but much further research is required.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.