People are not good at dealing with randomness. We tend to perceive patterns that aren't there. One example of this is the hot-hand bias: the tendency to perceive streaks in sequential events when the probabilities are in fact random.

This phenomenon was first noticed in basketball. Both fans and players erroneously believe a player's chance of making a basket are greater following a hit than following a miss. But studies show each shot is statistically independent from the previous one. Whether a player has made the previous shot is completely irrelevant for predicting whether he or she will make the next one.

The hot-hand bias appears to be universal in humans, found across cultures. But is it even more widespread — in our primate relatives?

Hot-Handed Monkeys

Tommy Blanchard, Andreas Wilke, and Benjamin Hayden investigated whether rhesus macaques show the hot-hand bias. The monkeys' task was to make a prediction of whether a stimulus would appear to their left or their right, and they indicated their choice by looking in the appropriate direction.

Blanchard and his colleagues manipulated the degree to which sequential stimuli were correlated. The stimuli were on a spectrum from very highly positively correlated, to random, to very negatively correlated. "The more highly positively correlated, the more often you'll end up getting streaks. The stronger the negative correlation, the more often things are going to alternate," Blanchard says.

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Blanchard and his colleagues tested many levels of correlation on the spectrum from highly positively correlated to highly negatively correlated. They found a significant hot-hand bias in the monkeys.

"They were able to perform the task quite well overall, but they were biased to thinking stimuli were streakier, or more positively correlated, than they actually were," says Blanchard.

Seeing Patterns

The universality of the hot-hand bias across human cultures, along with its presence in our primate relatives, suggests it could have an adaptive value.

Over most of our evolutionary history, humans were hunters and gatherers. In the wild, resources are not usually randomly distributed.

"If you find an apple laying around somewhere, chances are you're going to find other apples nearby," says Blanchard. "The reason for that is there's probably an apple tree nearby. And if you find one apple tree, there's likely more apple trees in the area, as well."

The types of food that primates forage for tend to form in clusters like this. This may have led to the evolved tendency to see patterns and resulted in the hot-hand bias we know today.

"Humans, and macaques, might be particularly likely to see these positive correlations because it was beneficial to catch them when they did exist, as they often did in their foraging environments," Blanchard says.

Reference:

Blanchard, T. C., Wilke, A., and Hayden, B. Y. (2014). Hot-Hand Bias in Rhesus Monkeys. Journal of Experimental Psychology: Animal Learning and Cognition 40(3): 280-286. doi: 10.1037/xan0000033.