Self-initiated gait increases susceptibility to the moving platform after-effect.

Walking onto a stationary platform previously experienced as moving results in a large forward sway, despite awareness of the changing context. This after-effect demonstrates aberrant motor prediction. Here, we compared after-effect magnitude when gait initiation was either externally triggered or self-initiated. Both participant groups adapted their walking speed similarly when walking onto the moving platform. When it was kept stationary however, after-effect magnitude was more than doubled in the self-initiated group. We attribute this to a stronger association made between the action (gait initiation) and its consequence (platform movement) when the action is initiated by oneself. This increased sense of agency reduces the ability to switch off the acquired motor response when it is no longer appropriate.