Partner's Actions Research Articles

Competition is crucial for social comparison processes in long-tailed macaques.

Humans modulate their self-evaluations and behaviour as a function of conspecific presence and performance. In this study, we tested for the presence of human-like social comparison effects in long-tailed macaques ( Macaca fascicularis). The monkeys' task was to extract food from an apparatus by pulling drawers within reach and we measured latency between drawer pulls. Subjects either worked on the task with a partner who could access the apparatus from an adjacent cage, worked in the absence of a conspecific but with food moving towards the partner's side or worked next to a partner who was denied apparatus access. We further manipulated partner performance and competitiveness of the set-up. We found no indication that long-tailed macaques compare their performance to the performance of conspecifics. They were not affected by the mere presence of the partner but they paid close attention to the partner's actions when they were consequential for food availability. If social comparison processes are present in long-tailed macaques, the present study suggests they may only manifest in situations involving direct competition and would thus be different from social comparisons in humans, which manifest also in the absence of direct competition, for example in evaluative contexts.

Reciprocal information flow and role distribution support joint action coordination

Many joint actions require task partners to temporally coordinate actions that follow different spatial patterns. This creates the need to find trade-offs between temporal coordination and spatial alignment. To study coordination under incongruent spatial and temporal demands, we devised a novel coordination task that required task partners to synchronize their actions while tracing different shapes that implied conflicting velocity profiles. In three experiments, we investigated whether coordination under incongruent demands is best achieved through mutually coupled predictions or through a clear role distribution with only one task partner adjusting to the other. Participants solved the task of trading off spatial and temporal coordination demands equally well when mutually perceiving each other’s actions without any role distribution, and when acting in a leader-follower configuration where the leader was unable to see the follower’s actions. Coordination was significantly worse when task partners who had been assigned roles could see each other’s actions. These findings make three contributions to our understanding of coordination mechanisms in joint action. First, they show that mutual prediction facilitates coordination under incongruent demands, demonstrating the importance of coupled predictive models in a wide range of coordination contexts. Second, they show that mutual alignment of velocity profiles in the absence of a leader-follower dynamic is more wide-spread than previously thought. Finally, they show that role distribution can result in equally effective coordination as mutual prediction without role assignment, provided that the role distribution is not arbitrarily imposed but determined by (lack of) perceptual access to a partner’s actions.

Couples' daily self-regulation: The Health Action Process Approach at the dyadic level

ObjectiveRegulating health behavior change often occurs in a dyadic context of romantic relationships. Dyadic approaches to standard health behavior change models are, however, barely considered. We investigated volitional processes of the Health Action Process Approach model for two health behaviors within a dyadic context of romantic couples. Specifically, we tested whether day-to-day volitional self-regulation predicted one’s own and one’s partner’s cigarettes smoked (Study 1) and physical activity (Study 2).MethodsIn two dyadic intensive longitudinal studies (Study 1: 83 dual-smoker couples intending to jointly quit smoking; Study 2: 61 overweight couples intending to become physically active), heterosexual partners independently reported on intention, self-efficacy, action planning, and action control in end-of-day diaries. In Study 1, daily number of cigarettes smoked was assessed via self-report. In Study 2, daily moderate-to-vigorous physical activity (MVPA) was assessed objectively via accelerometers. In both studies, dyadic cross-lagged intensive longitudinal analyses based on the Actor-Partner Interdependence Model were applied.ResultsAcross both studies, individual’s own volitional self-regulation positively predicted one’s own health behavior (less cigarettes smoked and more MVPA). One’s partner’s action control and intention also positively predicted one’s own health behavior. A marginal partner effect for self-efficacy was found in the context of smoking only.ConclusionsBehavioral self-regulation is not only relevant for individuals themselves, but some volitional processes may spill over to their partners. This highlights the need to specify couple-level processes involved in health behavior change, and to consider a social context of self-regulation.

Transitory Inhibition of the Left Anterior Intraparietal Sulcus Impairs Joint Actions: A Continuous Theta-Burst Stimulation Study.

Although temporal coordination is a hallmark of motor interactions, joint action (JA) partners do not simply synchronize; rather, they dynamically adapt to each other to achieve a joint goal. We created a novel paradigm to tease apart the processes underlying synchronization and JA and tested the causal contribution of the left anterior intraparietal sulcus (aIPS) in these behaviors. Participants had to synchronize their congruent or incongruent movements with a virtual partner in two conditions: (i) being instructed on what specific action to perform, independently from what action the partner performed (synchronization), and (ii) being instructed to adapt online to the partner's action (JA). Offline noninvasive inhibitory brain stimulation (continuous theta-burst stimulation) over the left aIPS selectively modulated interpersonal synchrony in JA by boosting synchrony during congruent interactions and impairing it during incongruent ones, while leaving performance in the synchronization condition unaffected. These results suggest that the left aIPS plays a causal role in supporting online adaptation to a partner's action goal, whereas it is not necessarily engaged in social situations where the goal of the partner is irrelevant. This indicates that, during JAs, the integration of one's own and the partner's action goal is supported by aIPS.

Observations on Cooperation

We study environments in which agents are randomly matched to play a Prisoner's Dilemma, and each player observes a few of the partner's past actions against previous opponents. We depart from the existing related literature by allowing a small fraction of the population to be commitment types. The presence of committed agents destabilizes previously proposed mechanisms for sustaining cooperation. We present a novel intuitive combination of strategies that sustains cooperation in various environments. Moreover, we show that under an additional assumption of stationarity, this combination of strategies is essentially the unique mechanism to support full cooperation, and it is robust to various perturbations. Finally, we extend the results to a setup in which agents also observe actions played by past opponents against the current partner, and we characterize which observation structure is optimal for sustaining cooperation.

How preschoolers and adults represent their joint action partner's behavior.

We investigated the cognitive mechanisms underlying turn-taking joint action in 42-month-old children (Experiment 1) and adults (Experiment 2) using a behavioral task of dressing a virtual bear together. We aimed to investigate how participants represent a partners' behavior, i.e., in terms of specific action kinematics or of action effects. The bear was dressed by pressing a smaller and a bigger button. In the Action-response task, instructions asked participants to respond to the partner by pressing the same or opposite button; in the Action-effect task they had to respond to the partner's action effect by dressing the bear with the lacking part of the clothing, which in some cases implied pressing the same button and in other cases implied pressing the opposite button. In 50% of the trials, the partner's association between each button and the ensuing effect (dressing the bear with t-shirt or pants) was reversed, while it never changed for participants. Both children and adults showed no effect of physical congruency of actions, but showed impaired performance in the Action-effect task if their partner achieved her effect through a different action-effect association than their own. These results suggest that, when encoding their partner's actions, agents are influenced by action-effect associations that they learnt through their own experience. While interference led to overt errors in children, it caused longer reaction times in adults, suggesting that a flexible cognitive control (that is still in development in young children) is required to take on the partner's perspective.

How You Move Is What I See: Planning an Action Biases a Partner's Visual Search.

Activating action representations can modulate perceptual processing of action-relevant dimensions, indicative of a common-coding of perception and action. When two or more agents work together in joint action, individual agents often need to consider not only their own actions and their effects on the world, but also predict the actions of a co-acting partner. If in these situations the action of a partner is represented in a functionally equivalent way to the agent’s own actions, one may also expect interaction effects between action and perception across jointly acting individuals. The present study investigated whether the action of a co-acting partner may modulate an agent’s perception. The “performer” prepared a grasping or pointing movement toward a physical target while the “searcher” performed a visual search task. The performer’s planned action impaired the searcher’s perceptual performance when the search target dimension was relevant to the performer’s movement execution. These results demonstrate an action-induced modulation of perceptual processes across participants and indicate that agents represent their partner’s action by employing the same perceptual system they use to represent an own action. We suggest that task representations in joint action operate along multiple levels of a cross-brain predictive coding system, which provides agents with information about a partner’s actions when they coordinate to reach a common goal.

Priority for one's own stimulus in joint performance: evidence from an event-related potential study.

To investigate priority of shared task representations (own vs. other) formed during joint task performance, event-related potentials were recorded while participants performed an auditory three-stimulus oddball task alone (individual condition) and with another participant (joint condition). Participants were required to discriminate between frequent standard tones and rare target tones, while ignoring nontargets assigned to a partner's action (i.e. no-go stimuli for one's own task performance). The parietal P3b was elicited for targets under both conditions. In contrast, P3b for nontargets was observed only in the joint condition, and in addition, it accompanied the frontal no-go P3. This implies that coactors share one another's task representations. Importantly, the emergence of P3b and no-go P3 for nontargets was delayed compared with P3b for targets, suggesting that shared task representations are serially applied to the stimulus processing and that one's own representations precede the other individual's representations.

Planning my actions to accommodate yours: joint action development during early childhood.

The planning and adjusting of one's actions in relation to an action partner is fundamental to smooth joint action. During their first years of life, children gradually become more engaged in joint actions. Here, we investigated whether and at what age children take their partner into account in their action plans to accommodate the other's actions. We focused on children's proactive planning (without prior experience) and flexible adjustment of action plans over time. In a behavioural study, we tested 96 children from four age groups (2½, 3, 3½ and 5 years) in a joint cup-stacking task. Children passed cups to their partner who had only one hand available (alternating over time) to build a tower. Children's response choices were assessed (i.e. passing the cup on the free or occupied side to their partner). The study yielded two major findings. At all ages, children proactively planned their actions in a way that accommodated their partner's actions. However, only by 3½ years did children start to flexibly integrate their partner into their action plans. Even at age 5, children only showed minimal adjustments to their action partner. Candidate processes underlying these developmental changes (e.g. inhibitory control, cognitive flexibility, perspective taking) are discussed.

Acting for the Greater Good: Identification with Group Determines Choices in Sequential Contribution Dilemmas

AbstractIn mixed‐motive interactions, defection is the rational and common response to the defection of others. In some cases, however, group members not only cooperate in the face of defection but also compensate for the shortfalls caused by others' defection. In one field and two lab studies, we examined when group members were willing to compensate for versus match defection using sequential dilemmas. We found that the level of identification with the broader group increased willingness to compensate for intragroup defection, even when it was personally costly. Compensating for a defecting partner's actions, however, is not an act of unconditional cooperation: It is accompanied by a lack of trust in the errant group member and a desire to be perceived as more ethical. Cooperation by others, on the other hand, is matched independent of whether the cooperator was an in‐group or out‐group member. We find similar patterns of compensation and matching when the personal cost involved contributing money or effort. Copyright © 2015 John Wiley & Sons, Ltd.

Modulation of Rolandic Beta-Band Oscillations during Motor Simulation of Joint Actions.

Successful joint actions require precise temporal and spatial coordination between individuals who aim to achieve a common goal. A growing number of behavioral data suggest that to efficiently couple and coordinate a joint task, the actors have to represent both own and the partner’s actions. However it is unclear how the motor system is specifically recruited for joint actions. To find out how the goal and the presence of the partner’s hand can impact the motor activity during joint action, we assessed the functional state of 16 participants’ motor cortex during observation and associated motor imagery of joint actions, individual actions, and non-goal-directed actions performed with either 1 or 2 hands. As an indicator of the functional state of the motor cortex, we used the reactivity of the rolandic magnetoencephalographic (MEG) beta rhythm following median-nerve stimulation. Motor imagery combined with action observation was associated with activation of the observer’s motor cortex, mainly in the hemisphere contralateral to the viewed (and at the same time imagined) hand actions. The motor-cortex involvement was enhanced when the goal of the actions was visible but also, in the ipsilateral hemisphere, when the partner’s hand was visible in the display. During joint action, the partner’s action, in addition to the participant’s own action, thus seems to be represented in the motor cortex so that it can be triggered by the mere presence of an acting hand in the peripersonal space.

Does the anticipation of compatible partner reactions facilitate action planning in joint tasks?

Observing another human's actions influences action planning, but what about merely anticipating them? In joint action settings where a partner's subsequent actions are a consequence of one's own actions, such contingent partner reactions can be regarded as action effects. Therefore, just like automatic effects they might facilitate those of a person's actions that overlap with them in relevant features. In Experiments 1 and 2, the spatial compatibility of contingent partner reactions was manipulated and compared with the influence of automatic effects. Experiment 1 used a simplistic scenario in which lateral keypress actions by the subject were responded to by mouse movements of a partner producing spatially compatible or incompatible visual effects. Experiment 2 transferred the paradigm to a more complex task in which subjects manually relocated virtual objects on a multi-touch display, and these or other objects were subsequently manipulated by the partner. In Experiment 1, compatible partner reactions speeded up subjects' preceding actions, whereas in Experiment 2 the influence was not statistically reliable. To test whether influences of partner reaction compatibility could be found in such naturalistic settings at all, Experiment 3 also used a multi-touch setting but varied temporal instead of spatial compatibility, which has several methodological advantages. This time, a compatibility effect emerged in subjects' movement initiation times, whereas contrast effects were found for movement durations. These findings indicate that the principles of ideomotor action control can be extended to joint action settings. At the same time, they also emphasize the importance of task features in determining whether our own behaviour is influenced by anticipations of another person's reactions.

Global understandings of domestic violence

Global understandings of domestic violence

Prejudiced interactions: implicit racial bias reduces predictive simulation during joint action with an out-group avatar.

During social interactions people automatically apply stereotypes in order to rapidly categorize others. Racial differences are among the most powerful cues that drive these categorizations and modulate our emotional and cognitive reactivity to others. We investigated whether implicit racial bias may also shape hand kinematics during the execution of realistic joint actions with virtual in- and out-group partners. Caucasian participants were required to perform synchronous imitative or complementary reach-to-grasp movements with avatars that had different skin color (white and black) but showed identical action kinematics. Results demonstrate that stronger visuo-motor interference (indexed here as hand kinematics differences between complementary and imitative actions) emerged: i) when participants were required to predict the partner's action goal in order to on-line adapt their own movements accordingly; ii) during interactions with the in-group partner, indicating the partner's racial membership modulates interactive behaviors. Importantly, the in-group/out-group effect positively correlated with the implicit racial bias of each participant. Thus visuo-motor interference during joint action, likely reflecting predictive embodied simulation of the partner's movements, is affected by cultural inter-individual differences.

Stable Observable Behavior

We study environments in which agents are randomly matched to play a Prisoner's Dilemma, and each player observes a few of the partner's past actions against previous opponents. We depart from the existing literature in two key respects: (1) we allow a small fraction of the population to be commitment types, and (2) we do not assume a time zero at which the entire community starts to interact. The presence of committed agents destabilizes all previously proposed mechanisms for sustaining cooperation. We present a novel mechanism (involving an essentially unique strategy combination) that sustains stable cooperation in many environments.

My partner is also on my mind: social context modulates the N1 response.

When individuals share a task with a partner, one's own actions and one's partner's actions have to be precisely tuned to one another. With behavioral means, it has been numerously shown that splitting a simple reaction time task between two participants produces similar interference patterns to those occurring when controlling the whole task on one's own. Less is known about the neuronal correlates when sharing a task with a partner. The processes of agent identification ("my turn" vs. "my partner's turn") were the focus of this study. In an EEG study, pairs of participants responded to different action-associated stimuli in a Go/NoGo paradigm. The same task was performed together with a partner (joint Go/NoGo condition) and when a partner was not present (single Go/NoGo condition). This study showed a top-down influence of social setting on early visual processing as indexed by the Go-N1 and NoGo-N1 response. This effect was only present in the joint Go/NoGo condition. It was particularly present in those trials where the partner did not have to act. Taken together, these results yield evidence for an early top-down influence of social setting on early processes of stimulus identification and differentiation.

Motor contagion during human-human and human-robot interaction.

Motor resonance mechanisms are known to affect humans' ability to interact with others, yielding the kind of “mutual understanding” that is the basis of social interaction. However, it remains unclear how the partner's action features combine or compete to promote or prevent motor resonance during interaction. To clarify this point, the present study tested whether and how the nature of the visual stimulus and the properties of the observed actions influence observer's motor response, being motor contagion one of the behavioral manifestations of motor resonance. Participants observed a humanoid robot and a human agent move their hands into a pre-specified final position or put an object into a container at various velocities. Their movements, both in the object- and non-object- directed conditions, were characterized by either a smooth/curvilinear or a jerky/segmented trajectory. These trajectories were covered with biological or non-biological kinematics (the latter only by the humanoid robot). After action observation, participants were requested to either reach the indicated final position or to transport a similar object into another container. Results showed that motor contagion appeared for both the interactive partner except when the humanoid robot violated the biological laws of motion. These findings suggest that the observer may transiently match his/her own motor repertoire to that of the observed agent. This matching might mediate the activation of motor resonance, and modulate the spontaneity and the pleasantness of the interaction, whatever the nature of the communication partner.

Teaching robots to cooperate with humans in dynamic manipulation tasks based on multi-modal human-in-the-loop approach

We propose an approach to efficiently teach robots how to perform dynamic manipulation tasks in cooperation with a human partner. The approach utilises human sensorimotor learning ability where the human tutor controls the robot through a multi-modal interface to make it perform the desired task. During the tutoring, the robot simultaneously learns the action policy of the tutor and through time gains full autonomy. We demonstrate our approach by an experiment where we taught a robot how to perform a wood sawing task with a human partner using a two-person cross-cut saw. The challenge of this experiment is that it requires precise coordination of the robot's motion and compliance according to the partner's actions. To transfer the sawing skill from the tutor to the robot we used Locally Weighted Regression for trajectory generalisation, and adaptive oscillators for adaptation of the robot to the partner's motion.

Monitoring Individual and Joint Action Outcomes in Duet Music Performance

We investigated whether people monitor the outcomes of their own and their partners' individual actions as well as the outcome of their combined actions when performing joint actions together. Pairs of pianists memorized both parts of a piano duet. Each pianist then performed one part while their partner performed the other; EEG was recorded from both. Auditory outcomes (pitches) associated with keystrokes produced by the pianists were occasionally altered in a way that either did or did not affect the joint auditory outcome (i.e., the harmony of a chord produced by the two pianists' combined pitches). Altered auditory outcomes elicited a feedback-related negativity whether they occurred in the pianist's own part or the partner's part, and whether they affected individual or joint action outcomes. Altered auditory outcomes also elicited a P300 whose amplitude was larger when the alteration affected the joint outcome compared with individual outcomes and when the alteration affected the pianist's own part compared with the partner's part. Thus, musicians engaged in joint actions monitor their own and their partner's actions as well as their combined action outcomes, while at the same time maintaining a distinction between their own and others' actions and between individual and joint outcomes.

Gaze transfer in remote cooperation: Is it always helpful to see what your partner is attending to?

Establishing common ground in remote cooperation is challenging because nonverbal means of ambiguity resolution are limited. In such settings, information about a partner's gaze can support cooperative performance, but it is not yet clear whether and to what extent the abundance of information reflected in gaze comes at a cost. Specifically, in tasks that mainly rely on spatial referencing, gaze transfer might be distracting and leave the partner uncertain about the meaning of the gaze cursor. To examine this question, we let pairs of participants perform a joint puzzle task. One partner knew the solution and instructed the other partner's actions by (1) gaze, (2) speech, (3) gaze and speech, or (4) mouse and speech. Based on these instructions, the acting partner moved the pieces under conditions of high or low autonomy. Performance was better when using either gaze or mouse transfer compared to speech alone. However, in contrast to the mouse, gaze transfer induced uncertainty, evidenced in delayed responses to the cursor. Also, participants tried to resolve ambiguities by engaging in more verbal effort, formulating more explicit object descriptions and fewer deictic references. Thus, gaze transfer seems to increase uncertainty and ambiguity, thereby complicating grounding in this spatial referencing task. The results highlight the importance of closely examining task characteristics when considering gaze transfer as a means of support.