© 2016, Springer-Verlag Berlin Heidelberg. Group living can present unique challenges that may require individuals to possess cognitive skills, such as the ability to recognise group members and maintain relationships with specific individuals. These skills may be particularly important for animals that live in large groups, because the intricacies of social life may become more complex when more individuals are involved. Previous research has found that species with regular social interactions tend to show elevated cognitive performance relative to those that rarely interact, yet intraspecific variation in performance among individuals in social groups of varying size is rarely explored. We investigated the relationship between the ability to solve an associative learning task and group size among individuals of a free-living, social bird, the Australian magpie (Cracticus tibicen dorsalis). Individuals varied in their likelihood of interacting with and solving the task. Individuals from larger groups were more likely to approach the associative learning task, suggesting that group size influences individual propensity to attempt a novel task. However, group size did not influence the likelihood that individuals solved the task. Rather, age had an important effect; adults were more likely to solve the association task than juveniles. Our finding that free-living individuals occurring in large social groups were more likely to interact with a novel task suggests that group size may affect differences in performance at a cognitive task within a species.