Canadian and British researchers have found a way to get rats to reason like human gamblers — something that they hope will help them develop drug treatments for people with gambling problems.
Once the rats had figured out the level of risk and reward associated with each possible option within a laboratory game, the scientists altered the animals' brain chemistry to mimic that of problem gamblers — and found that this led the rats to take unreasonably big risks, reported the study published Wednesday in the journal Neuropsychopharmacology.
"They weren't as good at telling what was the best option anymore," said Catharine Winstanley, a University of British Columbia psychologist who co-authored the study, along with her graduate student Fiona Zeeb and University of Cambridge psychologist Trevor Robbins.
Because the rats appear to reason and to respond to brain chemistry changes like human gamblers, the researchers are hoping that studying the rats can help them learn more about human gamblers, Winstanley said.
Next, they hope to look at what parts of a rat's brain are involved in gambling, how gambling behaviour and brain activity differ among individuals, and how a rich or poor social environment influences the risks of developing a gambling problem, as it appears to in humans. Ultimately, Winstanley added, they hope to come up with a drug treatment for human problem gamblers.
The task developed for the rats included four options where rats could get chances to "win" sugar pellets during a given period of time. Each time they lost, there was a time-out during which they could not play. Certain options allowed them to potentially earn more sugar pellets at once, but if they lost, they would have to sit through a longer timeout. The game was set up so that rats could earn the most within the allotted time by choosing smaller risks and rewards — something normal rats learned.
Animals play odds in wild: researcher
"If you think about what animals have to do in the wild, they're always faced with uncertainty in their decision making," Winstanley said. For example, they might have to decide whether to risk spending more energy to forage farther away, where there could, but might not be, more food. "So from that perspective, it may not be very surprising that they can gamble in this way."
The lab rat gambling task was intended to be similar to a game used to study gambling in humans, which tests the type of reasoning used in racetrack betting or deciding whether to hit or stand in blackjack.
Researchers had found that humans with gambling problems tended to take bigger risks in those tasks. Such humans have lower levels of seratonin — a brain chemical associated with impulse control.
Winstanley and her colleagues found that using drugs to lower a rats' serotonin levels made them perform more poorly in a similar gambling task.
Lowering the rats' dopamine levels, a chemical associated with pleasure, made the rats perform better, something consistent with human gambling experiments.
Other scientists have developed gambling tasks for animals in the past, but they involved smaller or bigger "wins" and did not involve losses. Such experiments were not influenced in the same way by brain chemicals such as serotonin, Winstanley and her colleagues found.
"What this seems to indicate is if all you have to worry about is failing to win, then different brain systems are engaged than if you have to worry about losing."