Associative learning in pairs tends to reduce individual differences in performance: An experiment with zebra finches...

The maintenance of individual differences in cognitive performance is puzzling given that cognitive performance is frequently correlated with fitness components. Cognitive performances are typically measured under laboratory conditions, in which individuals cannot observe others. Under natural conditions, however, observational learning would allow individuals with poorer cognitive abilities to improve their performance by copying the choices of more skilled individuals. Learning in groups would thus reduce differences in individual performance and, as such, might contribute to maintaining variability in cognitive abilities. Here, we carried out an experiment with zebra finches (Taeniopygia guttata) that were subjected to 3 associative learning tests, differing in terms of access to and complexity of public information. We found that the difference in learning performance between the fast and slow learners in the individual learning task was no longer significant when the slow learners had access to public information, but only if they received the same reward as their partner when choosing the same option. Thus, our study confirms that zebra finches tend to copy others' decisions that perform better, and hence strongly suggests that individual variation in cognitive performance, when tested in isolation, may not accurately reflect actual foraging success in a natural social setting. In species that forage in groups and use social information, our findings thus might contribute to explaining i) the maintenance of individual differences in cognitive abilities, and ii) why cognitive performances are not necessarily used as mate choice criteria. To better understand the evolution of animal cognition, future studies will thus need to identify which are the relevant cognitive abilities on which selection may act and measure individuals' cognitive performance in their natural environment.