Action Intentions and the Puzzle of Non-Willed Behaviour
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It feels intuitive that our actions are intentional, but there is considerable debate about whether (and how) humans control their behaviour. Ideomotor models of action argue that action intentions have a fundamentally perceptual format. In these views, actions are not only controlled by anticipating – imagining – their intended perceptual consequences but are also initiated when this “action effect” activation is sufficiently strong. Yet, this latter initiating function of action effect activation has not yet been tested directly.
In Experiments 1-4, 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, the combined activity from imagery and perception was sufficient to trigger non-willed action slips, even when participants were asked to withhold responses. The experiments provided the first direct evidence that forming an action intention may involve nothing more than evoking a strong enough mental image of the perceptual effect one wishes to achieve until a motor threshold is reached and the corresponding action is initiated. Experiments 5-6 showed that anticipated action effects attain this initiating role when they are treated as potential future goal states, rather than the current state of the sensorimotor system. Finally, Experiment 7 provided evidence that the tendency to produce action slips is positively associated with individual differences in ideomotor suggestibility.
These findings reveal how people are able to interact so effortlessly with the world by specifying lightly constraining action goals which mediate the translation of sensory input into motor output - allowing the environment to trigger actions which correspond with the goal. In addition, these findings suggest that action slips are a product of the same processes that guide voluntary actions. That is, perceptual input can co-opt endogenously activated action effects (e.g. via imagery) and, sometimes, trigger inappropriate behaviour.