Individual differences in great ape cognition across time and domains: stability, structure, and predictability

Variation in cognitive abilities is critical to understanding both the evolution and development of cognition. In this study, we examined the stability, structure, and predictability of individual differences in cognitive abilities in great apes across a broad range of domains, including social cognition, reasoning about quantities, executive functions, and inferential reasoning. We repeatedly administered six established tasks to N = 48 apes from four great ape species, spanning 10 sessions over 1.5 years. Task performance was most strongly predicted by stable, individual-specific characteristics rather than transient or group-level variables, highlighting the need for ontogenetic studies to understand cognitive variation in great apes. Furthermore, there were substantial correlations between tasks: associations between all non-social tasks were large and positive, suggesting shared cognitive processes. In contrast, tasks measuring social cognition were neither correlated with each other nor with non-social measures. Future studies of great ape cognition should build mechanistic models of cognitive processes to build an understanding of the evolution of cognition based on process-level commonalities across species.