The Gambler’s Fallacy Fallacy Fallacy (Commentary on Xiang et al., 2025)

Xiang et al. concluded that the gambler’s fallacy does not originate in biased beliefs. Reanalyzing their data, we arrived at the opposite conclusion. We show, more generally, that their main analysis—examining whether the median belief is biased—is not diagnostic of the presence of the gambler’s fallacy, whereas our test of the share of probability estimates for the streak ending above or below 50% is diagnostic. We also report results from a new study in which at least 80% of gambler’s-fallacy predictions originated in biased beliefs.