Rats Compulsively Gamble for Same Reason Humans Do: Lack of Serotonin

By Allison Bond | June 18, 2009 4:43 pm

ratRats in laboratory tests learned to gamble based on a system of punishments and rewards, strategizing like human gamblers. And when researchers tweaked the animals’ brain chemistry to mimic that of humans with a gambling addiction, the mice began taking risks like pathological gamblers, according to a study published in the journal Neuropsychopharmacology.

To create this animal model of gambling addiction, researchers created a system in which options that could bring greater rewards also could yield stronger punishment. In this case, however, instead of gambling for money, the rats aimed to get as many sugar pellets as possible. The rodents were placed in specially built boxes whose walls incorporated four “response holes.” Each opening was associated with a possibility of earning treats – from one up to four, depending on the aperture chosen. When an animal poked its snout into a hole, the movement would break an infra-red light across the opening, signaling a computer with a “probabilistic” reward-punishment schedule to assign a pellet win or a “timeout” loss. Playing against the clock, the rats had only 30 minutes to accumulate as many sugar pellets as they could [The Canadian Press].

The rats quickly caught on that by choosing the openings that offered the greatest number of pellets, they also risked the longest time-outs during which they could not play the game. The test was based on an evaluation for decision-making in humans called the Iowa Gambling Test. In that game, there are some “bad” decks of cards that offer high rewards and punishments, and other “good” decks that offer lesser rewards and punishments.

The animals learned that the best way to maximize the number of pellets was to play conservatively, and they began choosing openings that offered fewer pellets but lesser punishments, instead of risking long time-outs for a jackpot of pellets. But when the researchers lowered the rats’ levels of serotonin, a chemical associated with impulse control and depleted in addictive gamblers, the rats’ decision-making skills were impaired. They began taking bigger risks, just like human pathological gamblers. “They weren’t as good at telling what was the best option anymore,” said [co-author] Catharine Winstanley [CBC].

Scientists hope that the correlations between human and rat brain chemistry and gambling behavior put forth by the research will offer clues for treatment of gambling addictions and other impulse control disorders. Says Winstanley: “This coincides with data we’ve seen from pathological gamblers, who have been shown to have lower levels of serotonin in their brains…. This also ties in neatly with clinical findings in humans” [BBC].

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DISCOVER: Win Some, Lose More discusses the euphoria and gloom of gambling
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Image: iStockPhoto

CATEGORIZED UNDER: Health & Medicine, Mind & Brain
  • Jumblepudding

    I disagree. Human gambling is far more complex and high minded than the reward-seeking behavior of a rat chomping sugar pellets. Now excuse me, I need to get back to the tables.

  • http://drvitelli.typepad.com Romeo Vitelli

    Actually, gambling pretty much works the same whether you’re a human or a rat. It all comes down to reinforcement schedules and the possibility of a payoff.


  • StarDuff

    I have a tendency to believe this because the human body pretty much runs on chemicals emitted by the brain. The endocrine system is nothing short of amazing. These type of finding do not surprise me.

  • Matt

    @Jumblepudding: While you’re deciding whether or not to split those 8’s (SPLIT ‘EM!) consider that the serotonin levels in the brain seemed to affect the compulsive nature of gambling. At least the way I read the story, I don’t think that this would be a “cure to gambling”…just a way to treat those who have a chemical predilection towards destructive gambling behaviour. As you put it, the complex and high minded (really? high minded? Casino War is high minded?) nature of gambling will always have a place in entertainment. Long live the pair o’ dice!

  • Jason

    I wish I’d taken this up as a career.

    “What would you like to research next?”

    “Uh.. hm.. how about we get some rats addicted to gambling? We’ll need a big grant and lots of experimentation in Vegas.” /joke

    “That sounds great! Here’s your check.”

    “Wait I was..kidd..oh well.”

  • http://biospherenow.blogspot.com Mike from The Biosphere, Now.

    @Jason: I don’t think that’s quite how it goes. @Romeo I agree. Reward is is simple concept, regardless of brain complexity. It is worth thinking about that, and also worth experimenting with those thoughts.

  • mwl

    Corrupting rat’s morals! How low can you go?

  • mwl

    The depravity of secular science has gone too far.
    Science must be saved from immorality.
    I propose all research proposals be reveiwed by
    commitees of pious creation scientists to ensure
    consistency with scriptural standards.

  • Jules

    @MWL: When science falls under the realm of religion again “pious creation scientists,” are more than welcome, but until we revert back to the Dark Ages, they can keep studying their dusty old scrolls.

  • http://www..ws/PURSOR Pietr

    Why do they have to prove once again this obvious finding that has been known for decades. Dopamine is the reward neurotransmitter, serotonin is the inhibitor. Deficiencies in both or either contribute to inadequate impulse control.

    The answer is simple. To control not only gambling, other obsessive/compulsive but also addictive disorders, increase CNS serotonin and dopamine by administering their precursors in a balanced fashion. See website http://sites.google.com/site/pietrhitzig/


  • mwl

    Those were the days!


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