Abstract: Ramadan and Chess
Measuring Cognition at Scale: The Association Between Ramadan Exposure and Chess Performance
This paper studies the association between Ramadan exposure and cognition using casual online chess data. I construct a move-level dataset with roughly 16 million observations from about 800,000 games, combining engine evaluations and move-time information for players in Muslim-majority and non-Muslim-majority countries.
Using a difference-in-differences framework with player and period fixed effects, I find that Ramadan exposure is associated with improved decision quality, despite standard resource-depletion priors. Exposed players make fewer errors, lose fewer games, move faster, and shift toward more nocturnal play.
Because participation and play timing are voluntary, I implement additional mitigation checks; the main patterns remain. Heterogeneity results show that estimated cognitive gains are concentrated among lower-skill and lower-experience players.