Compared to external tones, previous studies found reduced N1 and P2 amplitudes in event-related potentials not only for self-generated tones, referred to as sensory attenuation, but also for tones generated by a person the participant observed. The P2 in this situation was attenuated, even when accounting for temporal predictability. P2 attenuation has also been related to the judgement of agency, which refers to explicit agency attribution. To test whether the P2 attenuation in action observation depends on the attribution of agency to a human agent, we added conditions with robotic hands performing the tone-eliciting action. Therefore, we compared N1 and P2 amplitudes of tones generated by an observed action of another person using either their own or a robotic hand, and by the computer shown as a robotic hand, with those of unpredictable external tones. Only N1 amplitudes in action observation with a human agent (human or robotic hand) were significantly attenuated compared to unpredictable external tones, while the N1 for the different observation conditions did not differ from each other. The P2 was attenuated for all action-observation conditions compared to unpredictable external tones, while again the amplitudes of the action-observation conditions did not differ from each other. Thus, while the threshold for N1 attenuation during action observation may be reached only if a human is observed, the P2 showed attenuation effects irrespective of agency attribution. This contrasts with previous findings for the P2 suggesting agency-related effects. Future research could further examine the modulation of attenuation by the action-observation setting. • Differences in sensory attenuation for action observation of different agents • Video implementation of human and robotic agency to be observed • N1 attenuation for tones generated by observed human agents only • P2 attenuation in all action-observation conditions
Egan et al. (Sun,) studied this question.