Learning by proportional observation in a species of fish

Theoretical analyses predict that animals should not copy other individuals indiscriminately but rather should do so selectively, according to evolved behavioral strategies that dictate the circumstances under which they copy. Here, we show experimentally that nine-spined sticklebacks (Pungitius pungnius) use social information in accordance with 1 of 3 theoretically predicted optimal strategies to guide their foraging behavior. Under test, sticklebacks copied the foraging patch choice of demonstrator individuals with a probability, proportional to the demonstrators' payoff. The observation of this highly efficient form of learning in a species of fish supports the view that the presence of enhanced social learning may be better predicted by specific sources of selection than by how closely the species is related to humans and sheds light on the character of an adaptive specialization in stickleback learning.