Tuesday, March 31, 2015

The hot-hands fallacy revisited

Aeon has a nice essay that points to recent empirical studies which appear to question one of the most famous cognitive biases - the 'Hot-Hand fallacy', or the mistaken perception of lucky streaks among sports persons.

In the first study, Andrew Bocskocsky, John Ezekowitz, and Carolyn Stein, examined videos of 83000 shot attempts from the 2012-13 US NBA season, and argue that a player in form is emboldened to take more difficult shots,
They showed, first of all, that players who felt 'hot' did in fact start taking harder shots. And, after controlling for the difficulty of each shot selected, they found a small yet significant hot-hands effect - that is, those who did well began to do even better over time. 
Another study, by Jeffrey Zwiebel and Brett Green, analyzed twelve years of data from Major League Baseball, and found that
how a player performed the most recent 25 times at bat was a significant predictor of how he would do the next time. They also calculated that a hot player was 30 per cent more likely to get a home run than if he were not on a winning streak. Lucky streaks are real and not just an illusion, they said. 
Yet another study by Juemin Xu and Nigel Harvey, which analyzed about half a million sports bets, found that those on winning streaks were much more likely than not to keep winning, and those on losing streaks were more likely to keep losing. They tried to understand the reasons why these streaks persisted,
As soon as bettors realized they were winning, they made safer bets, figuring their streaks could not last forever. In other words, they did not believe themselves to have hot hands that would stay hot. A different impulse drove gamblers who lost. Sure that lady luck was due for a visit, they fell for the gambler's fallacy and made riskier bets. As a  result, the winners kept winning (even if the amounts they won were small) and the losers kept losing. Risky bets are less likely to pay off than safe ones. The gamblers changed their behaviors because of their feelings about streaks, which in turn perpetuated those streaks. 

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