Experimental paradigms investigating the processing of self-induced stimuli are often based on the implicit assumption that motor processes are invariable regardless of their consequences: It is presumed that actions with different sets of predictable sensory consequences do not differ in their physical characteristics or in their brain signal reflections. The present experiment explored this assumption in the context of action-related auditory attenuation by comparing actions (pinches) with and without auditory consequences. The results show that motor processes are not invariable: Pinches eliciting a tone were softer than pinches without auditory effects. This indicates that self-induced auditory stimuli are not perceived as irrelevant side effects: The tones are used as feedback to optimize the tone-eliciting actions. The comparison of ERPs related to actions with different physical parameters (strong and soft pinches) revealed a significant ERP difference in the time range of the action-related N1 attenuation (strong pinches resulted in more negative amplitudes), suggesting that a motor correction bias may contribute to this auditory ERP attenuation effect, which is usually attributed to action-related predictive processes.

Human action planning relies on integrated representations of motor acts and the associated consequences, which implies that changing the set of effects associated to a motor act might directly influence action planning and control. The present study investigated the hypothesis that action-effect manipulations also affected the motor components of the actions even when only a single action option was available. Participants performed simple everyday actions (pinched a plastic sheet, pressed a button, tapped on a table) in two conditions. In the motor-auditory condition actions resulted in the presentation of a tone, whereas no tones were presented in the motor condition. The applied force was softer in the motor-auditory than in the motor condition for all three types of actions. The temporal characteristics of force application showed that action-effect related motor adaptation occurred during action planning, but possibly also during action execution. This demonstrates that even in simple, well-defined interactions with everyday devices we take all (even seemingly task-irrelevant) action-effects into account during action planning, which affects the motor component of the action. The results also imply that in experiments manipulating contingent action effects, one cannot rely on the assumption that the motor part of the action is invariant between conditions.