Monkeys Believe in Winning Streaks

Researchers have discovered that like humans, monkeys also believe in losing and winning streaks, even though these situations are, in fact, random.

The results suggest that "hot-hand bias" is not just an artifact picked up from childhood, but a belief that's inherited. It's suggested that this deeply rooted predisposition is 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.

To study this systematic error in primates and determine whether monkeys actually believe in winning streaks, researchers created a computer game that would be addicting to the animals.

"Luckily, monkeys love to gamble," Blanchard quipped, as stated in a press release.

The task consisted of rhesus monkeys choosing right or left, and receiving 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.

Monkeys quickly caught on to the correct sequence in the situations where there was a clear pattern; but in the random scenarios, they continued to make choices as if they expected a "streak." In other words, even when rewards were random, the monkeys favored one side.

Hot-hand bias was consistently obvious 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," Blanchard said.

Researchers speculate the cause for this thought process is not only because our brains, as well as those of monkeys, are equipped to look for patterns, but in the case of our primate relatives, food 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 co-author Benjamin Hayden, assistant professor brain and cognitive sciences at the University of Rochester.

Hayden and Blanchard reported their findings in the July issue of the Journal of Experimental Psychology: Animal Learning and Cognition.