Intention insertion: Activating an action's perceptual consequences is sufficient to induce non-willed motor behavior.

It feels intuitive that our actions are intentional, but there is considerable debate about whether (and how) humans control their motor behavior. Recent ideomotor theories of action argue that action intentions are fundamentally perceptual, that actions are not only controlled by anticipating-imagining-their intended perceptual consequences, but are also initiated when this action effect activation is strong. Here, the authors report a study (plus a replication) that provides direct evidence for this proposal, showing that even nonintended actions are executed when their effects are activated strongly enough. Participants mentally rehearsed a movement sequence and were unexpectedly presented with salient visual cues that were either compatible or incompatible with their currently imagined action. As predicted by ideomotor theories, the combined activation through imagery and perception was sufficient to trigger involuntary actions, even when participants were forewarned and asked to withhold them. Ideomotor cues, therefore, do not only influence preplanned responses but can effectively insert intentions to act, creating behavior de novo, as predicted from ideomotor theories of action control. (PsycINFO Database Record