Can you guess how many marbles are in a jar? Maybe you are a savant or maybe not; either way, odds are that, between them, a group of people will beat your guess.

Stefan Krause at the Lübeck University of Applied Sciences in Germany and his colleagues asked visitors to a museum to play the marble guessing game, and collected more than 2,000 guesses. When they made random groups out of these results, they found that the average guess of groups with 40 or more members was better than the best quarter of individual guesses, which implies that large groups of average ability are smarter than individual stars. The result suggests that, like schooling fish or swarming bees, humans can make fruitful use of collective decision-making, and that groups might outperform individuals of high ability — hinting at a selection pressure for diverse personalities.

Anim. Behav. 81, 941–948 (2011)