Reduced belief updating impairs adaptive step initiation in older adults

Ageing is associated with declines in mobility and balance that threaten independence and increase fall risk. Although these changes are often attributed to deterioration of muscular and sensory systems, growing evidence suggests that age-related alterations in cognitive control also contribute to postural instability and gait impairments. Here, we examined whether shifts in cognitive control strategy underlie impaired gait initiation in older adults by modelling how individuals update beliefs about upcoming actions. Older and younger adults performed a choice-stepping go/no-go task in which step likelihood was manipulated across trials. We measured anticipatory postural adjustments (APAs), the preparatory weight shifts preceding stepping and modelled age-related differences in APA onset using a hierarchical Bayesian framework. Older adults initiated slower APAs, particularly after repeated go trials. Computational modelling revealed reduced learning rates and heightened sensitivity to uncertainty in older adults, identifying altered belief updating as a cognitive mechanism shaping age-related changes in adaptive stepping.