Monkeys also believe in winning streaks, study shows

Jul 2, 2014

By Science Daily

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.

2 comments on “Monkeys also believe in winning streaks, study shows

  • 1
    God fearing Atheist says:

    Either the article or the original research needs to up its game.

    If I have to pick left or right button, and I figure out the correct button is a random 50/50 guess, I might as well keep hitting the same button, because that is as good a solution as any other (it is a Nash equilibrium solution), and quite probably saves mental and physical effort. If it does save any effort at all (=calories) then it is the NE solution in evolutionary terms. They might have proved the monkeys are smarter than the researchers.

    If a monkey repeated a press after a win, and swapped on a loss, it might indicate belief in “lucky streaks”, but that is not what the article above states – it states “favoured one side” not “the side of the last win”.

    Can we please have a definition of “free will” before someone pontificates on the solution.



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  • It is correct that even learning the correct button to press would be rational (and a rational adaptation to the environment). It’s the best solution, as you point out, and the concept of a NE isn’t even necessary to argue that. The authors themselves say as much (an adaptation to “clumpy” environments).
    The summary here of course leaves out some details, so I would encourage people to read the article.

    I would probably object to the article in this way: while humans demonstrably know that the generating process is stochastic (i.e., the correct choice is completely random), how are the monkeys supposed to know this? My second criticism would be that this sort of work looks at (primate) behavior through behaviorist eyes, where decisions simply come from learned stimulus-reward associations. Humans aren’t that simplistic, and those monkeys aren’t, either.



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