Gambling Monkeys Share Humans' Bias for the 'Hot Hand'

Rhesus monkeys and humans share 93 percent of their DNA, as well as at least one demonstrable cognitive bias.

In the basement, playing NBA Jam, it was fact: make three shots in a row, and you were on fire. Until your opponent scored, all but the longest full-court shots were going in—whether shot like a comet from “downtown” or thrown down in a flaming, triple-flip slam dunk.

But in reality, the hot hand phenomenon doesn't exist. Basketball shots are independent events, and the hot hand is just the flip side of the gambler's fallacy: After landing on red, the roulette wheel is just as likely to land on red the next spin. When LeBron fires off a three, it has more to do with where he's standing and who's in front of him than whether or not he made the previous shot.

But both basketball fans and players believe that the “hot hand” exists. I saw Steph Curry go berserk on the Knicks; I feel like its something I've witnessed, and there is some evidence to suggest it could play a factor. But when you come down to discrete events, the last shot you made isn't likely to affect the one you're about to throw up.

Researchers from the University of Rochester and Clarkson University just published research in the Journal of Experimental Psychology: Animal Learning and Cognition, explaining that we might all be wrong about the hot hand, but we're wrong for some reasons that are so deeply ingrained that even our fellow-primates believe in winning streaks.

The researchers set up three variations on a game where rhesus monkeys had a choice of either right or left, and received some juice or water for guessing correctly. Two of the games had clear patterns—either alternating the correct choice from side to side, or repeating it—while the third variation was completely random.

The monkeys didn't have trouble deducing the patterns and guessing the correct sequence in the first two variations. But during the random sequence, they kept choosing as if they expected a streak, demonstrating what's known as a win-stay bias. They 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 the study's lead author, Tommy Blanchard. The monkeys seemed to see—and therefore choose as though there were—more positively correlated sequences than there really were.

Studies of humans have found this tendency across cultures, and that it is the most pronounced in “foraging contexts.” And the researchers speculated that the circumstances that primates forage under informs our win-stay bias.

Finding valuable resources in clusters, like fruit in trees, or groups of grubs under a log, “is likely to have been the norm for most of the natural resources humans encountered over evolutionary time,” the study stated. “Natural resources that primates forage for, such as specific plants and animals, rarely distribute themselves in a purely random manner in their natural environment because individual organisms are not independent of one another.”

As for basketball, shots aren't entirely random, and so something like the Spurs' point-splosion to open Game 3 of this year's NBA Finals, or Steph Curry going 11 of 13 against the Knicks, is informed by things like judicious shot selection. Good looks weren't exactly hard to come by when the Spurs' crisp passing met the floundering Heat.

It's worth remembering that while Curry was stunning, his team actually lost that game to the Knicks, as the Knicks defense held all but two of Curry's teammates to single digits and the scheme left Raymond Felton covering Curry much of the game.

But that's not how I remember it. I remember Curry heating up; I remember him making a three every time I glanced up at the TV at the bar, with a tail of flames trailing the ball through the hoop. It's comforting, I guess, that the rhesus could relate, even if we're both wrong.