Imagine you're at a roulette table in Las Vegas.   You've been having an amazing run of luck (yes, it does happen on occasion).   After winning five times in a row using a can't-fail new system, do you become convinced that the next bet must pay off as well?   On the other hand, do you become convinced that the odds must turn and you change your bet instead?    Whichever way you decide, you are likely to fall prey to a basic misconception about probability.   Human beings are not very good at predicting random events.

A classic example occurred in the casino at Monte Carlo on August 18, 1913 when "black" came up fifteen times in a row on a roulette wheel.   Once word got around the casino, gamblers swarmed the roulette table and most bet on "red".   After all, the odds had to turn sometime, right?   As the wheel kept coming up "black", many gamblers doubled their stakes in the hope of winning.   By the time the magic streak ended after twenty-six turns, the casino had raked in millions.  The gamblers ended up poorer and also became a living example of what is known as the "gambler's fallacy". 

Defined as the belief that if something happens more frequently than normal during some period, then it will happen less frequently in the future, the gambler's fallacy has been the bane of countless gamblers the world over.   Investors can fall prey to it as well, usually when they're attempting to "time the market"  (trying to anticipate when a stock will rise or fall).

But what happens if you manage to guess right?   Athletes and gamblers often express their absolute faith in "winning streaks" which seem to contradict the laws of probability as we seem to understand them.   In that case, it is usually known as the "hot hand", or the belief that success in a random event will increase the probability of a similar success occurring in future.   Virtually any sports buff can give examples of spectacular winning streaks.   One recent example was in 2006 when Kobe Bryant scored 81 points for Los Angeles against my home team of Toronto (painful as this is to relate).  

First described in basketball, players,  athletes who had successfully made a shot often believe that their likelihood of making another shot has been increased as a result.  According to psychologists Thomas Gilovich, Amos Tversky and Robert Vallone in their original research on the hot hand, the sense of being "hot" that many people report tends not to be of any value in predicting future hits or misses.  Though psychological research has found that the "hot hand" is a myth and that one random event does not influence later events, the hot-hand bias is  commonly seen in athletes, gamblers, and even investors.  

Believing in "hot streaks"  can certainly affect the decision to invest in a mutual fund that seems able to "beat the street" on a consistent basis.   While belief that the fund manager is "hot" can actually work for a time, there is a good reason why "past performance does not guarantee future results" is a  standard warning with investment companies.   In fact, the hot-hand bias has been reported in cultures around the world and can influence decisions ranging from searching for food to finding a good parking spot.

But can it occur in non-humans as well?  While comparing certain behaviours across species is always difficult, primate species such as rhesus monkeys have a similar evolutionary history to humans and may be vulnerable to the same kind of biases seen in humans.   Research looking at foraging behaviour, such as hunting for food or shelter, suggests that primates (whether human or non-human), often rely on a hot-hand strategy of assuming that resources are "clumped" together rather than being randomly distributed.  Since this strategy often leads to positive results, at least in natural settings, some researchers have suggested that the hot-hand bias arose as part of our evolutionary history.

As a test of the hot-hand bias in non-human primates, a  new study published in the Journal of Experimental Psychology:  Animal Learning and Cognition presents the results of research ooking at how rhesus monkeys forage for food.     The results suggest that the hot-hand bias may be much older than anyone realizes.   It also may provide fresh insight into how the primate mind first evolved.

A team of researchers at the University of Rochester and Clarkson University examined three rhesus monkeys with a specialized gambling task intended to test the hot-hand bias.   Using a correlated outcomes task to measure whether monkeys changed their foraging behaviour based on previous success, the researchers found that the monkeys adopted a strategy very similar to what athletes and gamblers believing in the hot hand often use.   Over hundreds of trials, the hot-hand bias appears exceptionally strong and difficult for monkeys to overcome.   Even with specialized training to teach monkeys alternative strategies, they continue to favour the hot-hand approach. 

According to lead researcher Tommy C. Blanchard, one reason for the hot-hand bias in  animals could be that limited memory span makes them more likely to depend on recent successes and less likely to learn other strategies for foraging.  While the hot-hand bias isn't always successful, it works often enough to have become an evolutionary preference for primates.   The presence of the hot-hand bias in different primate species, including humans, suggests that believing in the hot hand has a very long evolutionary history.   

Since the need to forage was one of the factors that drove how our minds and brains evolved, primates (humans included) may have developed certain biases that automatically influence decision-making.   That includes relying on recent memories to find patterns in otherwise independent events (a.k.a.  the hot-hand bias).

While relying on the hot hand may have made sense with foraging behaviour in the wild, modern life is not quite so simple.   That doesn't mean that belief in the hot hand will ever go away however.  Even today, sports buffs, bloggers, and athletes all defend their own belief in "hot streaks" and denounce research studies that dare to suggest the opposite.  Gamblers still bet money on "sure things" that are more illusion than anything else, a trend that will likely continue in future.

Anyone care to bet against me?

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