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Scientists from Canada's University of British Columbia have built a casino for rats -- and found that not only do bright sounds and lights make rodents more prone to taking risks when gambling, but also that this risk-taking behaviour can be mitigated by dopamine blockers.

Michael M. Barrus and Catharine A. Winstanley of the university's Department of Psychology set up their 'rat casino' as part of an investigation into addictive behaviours. They taught 32 rats to gamble in order to win sugary treats, choosing between four different options that had varying likelihoods of providing either a treat or a punishing time-out period.


The optimal strategy for the rats was to always select the option which gave them smaller rewards, but carried less risk, rejecting "high-risk, high reward" options -- a behaviour which maximised their profits.

Under normal conditions, the rats learned what got them the most reliable pay-out and stuck with that. But once the scientists added lights and sound to the game, the rats' behaviour changed. Like human-oriented slot machines, large rewards produced more lights and music than more modest wins. Following these cues, the rats started taking greater risks to get those colourful, noisy pay-outs.

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Professor Catharine Winstanley said that "anyone who’s ever designed a casino game or played a gambling game will tell you that of course sound and light cues keep you more engaged, but now we can show it scientifically."


In a paper published in the Journal of Neuroscience, the researchers write that "rats' choice of the disadvantageous risky options was significantly greater on the cued task" -- in other words, the rats started consistently behaving like problem gamblers. This phenomenon increased when they gave the rats a drug that activated the D3 dopamine receptors in their brains, commonly associated with multiple forms of addiction.

However, when they administered a dopamine inhibitor to block the D3 receptor, the rats stopped exhibiting irrational gambling behaviours. The blocker had almost no effect on rats who gambled without the flashing lights and sound cues. "This brain receptor is also really important to drug addiction, so our findings help support the idea that risky behaviour across different vices might have a common biological cause," said lead author Michael Barrus

Prof Winstanley added that "I often feel that scientific models are decades behind the casinos. I don’t think it’s an accident that casinos are filled with lights and noise."