Motor-related cortical oscillations distinguish one's own from a partner's contributions to a joint action.

The ability to distinguish between one's own and others' actions is a requirement for successful joint action. Such a distinction might be supported by dissociable motor activity underlying each partner's individual contributions to the joint action. However, little research has directly compared motor activity associated with one's own vs. others' actions during joint action. The current study investigated whether motor-related cortical oscillations distinguish between self- and partner-produced actions when partners take turns producing taps to meet a joint timing goal. Across two experiments, the degree of beta suppression differentiated one's own from a partner's actions, with more suppression occurring during one's own actions than during a partner's actions. Self-partner differences in mu suppression were also evident, particularly when partners produced actions in succession. Increased beta suppression was also observed during partners' actions when they were followed by one's own actions, suggesting that the coordination demands imposed by the joint action could affect the pattern of beta reactivity during a turn-taking joint action. Together, these findings demonstrate that dynamic patterns of motor activity underpin successful joint action and that periods of distinct motor activity are associated with one's own contributions to a joint action.

The auditory P2 differentiates self- from partner-produced sounds during joint action: Contributions of self-specific attenuation and temporal orienting of attention.

Sensory attenuation of the auditory P2 event-related potential (ERP) has been shown to differentiate the sensory consequences of one's own from others' action in joint action contexts. However, recent evidence suggests that when people coordinate joint actions over time, temporal orienting of attention might simultaneously contribute to enhancing the auditory P2. The current study employed a joint tapping task in which partners produced tone sequences together to examine whether temporal orienting influences auditory ERP amplitudes during the time window of self-other differentiation. Our findings demonstrate that the combined requirements of coordinating with a partner toward a joint goal and immediately adjusting to the partner's tone timing enhance P2 amplitudes elicited by the partner's tone onsets. Furthermore, our findings replicate prior evidence for self-specific sensory attenuation of the auditory P2 in joint action, and additionally demonstrate that it occurs regardless of the coordination requirements between partners. Together, these findings provide evidence that temporal orienting and sensory attenuation both modulate the auditory P2 during joint action and suggest that both processes play a role in facilitating precise interpersonal coordination between partners.

Sensory Attenuation of the Auditory P2 Differentiates Self- from Partner-Produced Sounds during Joint Action.

Successful human interaction relies on people's ability to differentiate between the sensory consequences of their own and others' actions. Research in solo action contexts has identified sensory attenuation, that is, the selective perceptual or neural dampening of the sensory consequences of self-produced actions, as a potential marker of the distinction between self- and externally produced sensory consequences. However, very little research has examined whether sensory attenuation distinguishes self- from partner-produced sensory consequences in joint action contexts. The current study examined whether sensory attenuation of the auditory N1 or P2 ERPs distinguishes self- from partner-produced tones when pairs of people coordinate their actions to produce tone sequences that match a metronome pace. We did not find evidence of auditory N1 attenuation for either self- or partner-produced tones. Instead, the auditory P2 was attenuated for self-produced tones compared to partner-produced tones within the joint action. These findings indicate that self-specific attenuation of the auditory P2 differentiates the sensory consequences of one's own from others' actions during joint action. These findings also corroborate recent evidence that N1 attenuation may be driven by general rather than action-specific processes and support a recently proposed functional dissociation between auditory N1 and P2 attenuation.

The motor-related brain activity that supports joint action: A review.

Recent years have seen a rapid increase in research investigating the motor-related brain activity that supports joint action. This research has employed a variety of joint action tasks and an array of neuroimaging techniques, including fMRI, fNIRS, EEG, and TMS. In this review, we provide an overview of this research to delineate what is known about the motor-related brain activity that contributes to joint action and to highlight key questions for future research. Taken together, the surveyed research supports three major conclusions. First, the mere presence of a joint action context is sufficient to modulate motor activity elicited by observing others' actions. Second, joint action is supported by dissociable motor activity associated with a person's own actions, their partner's actions, and the joint action, and by between-brain coupling of motor-related oscillatory activity. Third, the structure of a joint action modulates the motor activity involved: Unique motor activity is associated with performing joint actions comprised of complementary actions and with holding the roles of leader and follower within a joint action. We conclude the review by highlighting overarching themes and key questions for future research.

The predictability of a partner's actions modulates the sense of joint agency.

When people coordinate their actions with others, they experience a sense of joint agency, i.e., shared control over actions and their consequences. The current study examined whether the predictability of others' actions modulates joint agency. Each participant coordinated with two confederate partners to produce tone sequences that matched a metronome pace. The timing of the confederates' actions was manipulated so that one partner's actions were highly predictable in time and the other's less predictable. After each sequence, participants rated their experience of joint agency on a scale from shared to independent control. People felt more shared control when they coordinated with the more predictable partner, even after controlling for their own performance accuracy and variability. Thus, people rely on predictions of others' actions to derive a sense of joint agency during interpersonal coordination.

Mutual coordination strengthens the sense of joint agency in cooperative joint action.

Philosophers have proposed that when people coordinate their actions with others they may experience a sense of joint agency, or shared control over actions and their effects. However, little empirical work has investigated the sense of joint agency. In the current study, pairs coordinated their actions to produce tone sequences and then rated their sense of joint agency on a scale ranging from shared to independent control. People felt more shared than independent control overall, confirming that people experience joint agency during joint action. Furthermore, people felt stronger joint agency when they (a) produced sequences that required mutual coordination compared to sequences in which only one partner had to coordinate with the other, (b) held the role of follower compared to leader, and (c) were better coordinated with their partner. Thus, the strength of joint agency is influenced by the degree to which people mutually coordinate with each other's actions.