Adaptive behavior in dynamic, uncertain environments requires joint cognitive and motor functions, which both undergo changes across the lifespan. Yet, their interaction across age is not well understood. We developed a combined reinforcement learning and rapid reaching task and tested children (6-9 years), adolescents (13-16 years), young adults (18-30 years), and older adults (65-80 years). Participants predicted the location of a butterfly under conditions of expected or additional unexpected uncertainty. After their prediction, the butterfly moved certain or uncertain direction, while participants rapidly reached toward its final position.
Consistent with an inverted-u-shaped age pattern, children and older adults showed lower cognitive performance and reduced adaptation to uncertainty. Difficulty learning from outcomes that disconfirmed predictions appeared to potentially underlie these differences. In the motor domain, children and older adults exhibited longer movement times, further prolonged by high motor uncertainty. Unexpectedly, they were spatially more efficient, suggesting lifespan differences in a spatiotemporal trade-off.
Importantly, cross-domain effects of uncertainty emerged: high cognitive uncertainty reduced motor performance, primarily by lowering spatial efficiency, while high motor uncertainty increased cognitive performance, associated with a greater reliance on learned prediction values. Cross-domain performances were correlated, specifically in children and young adults, and under high cognitive uncertainty. These findings advance a cross‑domain framework for lifespan adaptation and highlight the importance of integrating cognitive and motor processes in uncertain environments.