Humans exhibit a suite of changes in cognition across the lifespan, both in early development and during aging. Comparative patterns are crucial to infer the biological basis and evolutionary significance of human traits, but little is known about whether other primates show similar cognitive changes over development. I will present research examining the emergence of social cognition, spatial memory, and decision-making capacities across different primates that vary in socioecology and life history characteristics. I will use this comparative data to test when different developmental trajectories emerge, and how the pace and pattern of development shapes the expression of mature cognitive traits across species.