Monkeys also believe in winning streaks

Humans have a well-documented tendency to see winning and losing streaks in situations that, in fact, are random. But scientists disagree about whether the “hot-hand bias” is a cultural artifact picked up in childhood or a predisposition deeply ingrained in the structure of our cognitive architecture.

Now in the first study in non-human primates of this systematic error in decision making, researchers find that monkeys also share our unfounded belief in winning and losing streaks. The results suggests that the penchant to see patterns that actually don’t exist may be inherited—an evolutionary adaptation that may have provided our ancestors a selective advantage when foraging for food in the wild, according to lead author Tommy Blanchard, a doctoral candidate in brain and cognitive sciences at the University of Rochester.

The cognitive bias may be difficult to override even in situations that are truly random. This inborn tendency to feel that we are on a roll or in a slump may help explain why gambling can be so alluring and why the stock market is so prone to wild swings, said coauthor Benjamin Hayden, assistant professor brain and cognitive sciences at the University of Rochester.

Hayden, Blanchard, and Andreas Wilke, an assistant professor of psychology at Clarkson University, reported their findings in the July issue of the Journal of Experimental Psychology: Animal Learning and Cognition.

To measure whether monkeys actually believe in winning streaks, the researchers had to create a computerized game that was so captivating monkeys would want to play for hours. “Luckily, monkeys love to gamble,” said Blanchard. So the team devised a fast-paced task in which each monkey could choose right or left and receive a reward when they guessed correctly.

The researchers created three types of play, two with clear patterns (the correct answer tended to repeat on one side or to alternate from side to side) and a third in which the lucky pick was completely random. Where clear patterns existed, the three rhesus monkeys in the study quickly guessed the correct sequence. But in the random scenarios, the monkeys continued to make choices as if they expected a “streak”. In other words, even when rewards were random, the monkeys favored one side.

The monkeys showed the hot-hand bias consistently over weeks of play and an average of 1,244 trials per condition. “They had lots and lots of opportunities to get over this bias, to learn and change, and yet they continued to show the same tendency,” said Blanchard.

So why do monkeys and humans share this false belief in a run of luck even when faced over and over with evidence that the results are random? The authors speculate that the distribution of food in the wild, which is not random, may be the culprit. “If you find a nice juicy beetle on the underside of a log, this is pretty good evidence that there might be a beetle in a similar location nearby, because beetles, like most food sources, tend to live near each other,” explained Hayden.

Evolution has also primed our brains to look for patterns, added Hayden. “We have this incredible drive to see patterns in the world, and we also have this incredible drive to learn. I think it’s very related to why we like music, and why we like to do crossword puzzles, Sudoku, and things like that. If there’s a pattern there, we’re on top of it. And if there may or may not be a pattern there, that’s even more interesting.”

Understanding the hot-hand bias could inform treatment for gambling addiction and provide insights for investors, said Hayden. “If a belief in winning streaks is hardwired, then we may want to look for more rigorous retaining for individuals who cannot control their gambling. And investors should keep in mind that humans have an inherited bias to believe that if a stock goes up one day, it will continue to go up.”

The results also could provide nuance to our understanding of free will, said Blanchard, who was drawn to the study of decision making during prior graduate training in philosophy. “Biases in our decision-making mechanisms, like this bias towards belief in winning and losing streaks, say something really deep about what sorts of creatures we are. We often like to think we make decisions based only on the information we’re conscious of. But we’re not always aware of why we make certain decisions or believe certain things.

“We’re a complex mix of biases and heuristics and statistical reasoning. When you put it all together, that’s how you get sophisticated behavior. We don’t know where a lot of these biases come from, but this study—and others like it—suggest many of them are due to cognitive mechanisms we share with our primate relatives,” said Blanchard.

Scientists reduce behaviours associated with problem gambling in rats

With the help of a rat casino, University of British Columbia brain researchers have successfully reduced behaviours in rats that are commonly associated with compulsive gambling in humans.

The study, which featured the first successful modeling of slot machine-style gambling with rats in North America, is the first to show that problem gambling behaviours can be treated with drugs that block dopamine D4 receptors. The findings have been published in Biological Psychiatry journal.

“More work is needed, but these findings offer new hope for the treatment of gambling addiction, which is a growing public health concern,” says Paul Cocker, lead author of the study and a PhD student in UBC’s Dept. of Psychology. “This study sheds important new light on the brain processes involved with gambling and gambling addictions.”

For the study, rats gambled for sugar pellets using a slot machine-style device that featured three flashing lights and two levers they could push with their paws. The rats exhibited several behaviours associated with problem gambling such as the tendency to treat “near misses” similar to wins.

Building on previous research, the team focused on the dopamine D4 receptor, which has been linked to a variety of behavioural disorders, but never proven useful in treatment. The study found that rats treated with a dopamine D4 receptor-blocking medication exhibited reduced levels of behaviours associated with problem gambling.

While findings suggest that blocking the D4 dopamine receptor may help to reduce pathological gambling behaviours in humans, the researchers note that further research is needed before the drugs can be considered a viable pharmaceutical treatment for pathological gambling in humans.

BACKGROUND

“Pathological gambling is increasingly seen as a behavioural addiction similar to drug or alcohol addiction, but we know comparatively little about how to treat problem gambling,” says Cocker. “Our study is the first to show that by blocking these receptors we might be able to reduce the rewarding aspects of near-misses that appear to be important in gambling.”

Methods: In the 16-month study,a cohort of 32 laboratory rats responded to a series of three flashing lights before choosing between two levers. One combination of lights (all lights illuminated) signaled a win and seven combinations (zero, one or two lights) signaled a loss. A “cash-out” lever rewarded the rat with 10 sugar pellets on winning trials, but gave a 10-second “time out” penalty on losing trails. The “roll again” lever allowed the rats to begin a new trial without penalty, but provided no sugar pellets.

Interestingly, the rats showed a tendency towards choosing the cash-out lever when two lights (near-miss) illuminated, suggesting that rats, like people, are susceptible to the near-miss effect. By blocking the D4 receptors with drugs, the researchers were successfully able to reduce the rat’s choice of the “cash-out” lever on non-winning trials.

The D4 blocker drug used in the study has previously been tested on humans in attempts to treat behaviour disorders like schizophrenia but appeared to have no effect.

Near misses: This common cognitive bias is considered an important factor in the development of pathological gambling problems. The fact that slot machines tend to have a relatively high proportion of near-misses in comparison to other gambling games may be the reason that slot machines are such a particularly addictive form of gambling.

Study authors: Paul Cocker and Prof.Catharine Winstanley (UBC Dept. of Psychology), Bernard Le Foll (University of Toronto, Centre for Addiction and Mental Health) and Robert D. Rogers (Bangor University). The study, A Selective Role for Dopamine D4 Receptors in Modulating Reward Expectancy in a Rodent Slot Machine Task, is available upon request.

UBC’s Laboratory of Molecular and Behavioural Neuroscience, led by Psychology Prof. Catharine Winstanley, focuses on understanding the biological mechanisms of functions such as impulse control and gambling, leading to new and improved treatments for disorders like attention deficit hyperactivity disorder, bipolar disorder, personality disorders, and drug addiction.

Problem gambling: Compulsive gambling affects between three and five percent of North Americans, according to recent statistics.