Zebrafish are exceptionally good synchronised swimmers, forming tight schools that contain hundreds of individuals . Physicists have shown how the fish stay together even as they swim faster to avoid a predator – and they do so by subconsciously performing the kind of weighted averages calculation familiar to high-school mathematics students.

Small fishes tend to swim in schools. Sticking together decreases the risk of any individual fish being killed by predators , and biologists say a school of fish can have more foraging success because …