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Intra- and interpersonal interlimb coordination of pendulums swung from the wrist was investigated. For both kinds of coordination, the steady state and breakdown of bimanual rhythmic coordination as indexed by the time series of the relative phase angle phi were studied under the manipulation of coordination mode, frequency of oscillation, and the...
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... According to della Gatta et al., this suggests that participants represented the joint goal (drawing a circle and a line) motorically, almost as if they were performing the two actions with their own two hands. Thus, the intrapersonal motor coupling typically observed in bimanual coordination (Franz et al., 1991) emerged here in the form of interpersonal coupling (consistent with the account that coordination within and between individuals relies on similar processes (e.g., Fine & Amazeen, 2011;Richardson et al., 2007;Schmidt et al., 1998;Schmidt & Richardson, 2008)). ...
When acting jointly, individuals often attend and respond to the same object or spatial location in complementary ways (e.g., when passing a mug, one person grasps its handle with a precision grip; the other receives it with a whole-hand grip). At the same time, the spatial relation between individuals’ actions affects attentional orienting: one is slower to attend and respond to locations another person previously acted upon than to alternate locations (“social inhibition of return”, social IOR). Achieving joint goals (e.g., passing a mug), however, often requires complementary return responses to a co-actor’s previous location. This raises the question of whether attentional orienting, and hence the social IOR, is affected by the (joint) goal our actions are directed at. The present study addresses this question. Participants responded to cued locations on a computer screen, taking turns with a virtual co-actor. They pursued either an individual goal or performed complementary actions with the co-actor, in pursuit of a joint goal. Four experiments showed that the social IOR was significantly modulated when participant and co-actor pursued a joint goal. This suggests that attentional orienting is affected not only by the spatial but also by the social relation between two agents’ actions. Our findings thus extend research on interpersonal perception-action effects, showing that the way another agent’s perceived action shapes our own depends on whether we share a joint goal with that agent.
... tion ( Camazine et al., 2003 ;Pezzulo et al., 2019 ). As such, INS would be reminiscent of many other self-organized entrainment phenomena observed across very heterogeneous fields of research, including psychology ( Oullier et al., 2008 ;Richardson et al., 2007Richardson et al., , 2005Schmidt et al., 1998 ;Varlet et al., 2017 ), ethology ( Ballerini et al., 2008 ;Buhl et al., 2006 ;Cavagna et al., 2010 ;Couzin, 2007 ;Yates et al., 2009 ), or even physics ( Peña Ramirez et al., 2016 ;Von Humboldt, 1846 ). For instance, INS might be qualitatively similar to the spontaneous synchronization of behavioral states in multiple collective animal behavior like flocking in birds ( Ballerini et al., 2008 ), or swarms of insects ( Yates et al., 2009 ). ...
Synchronization of neural activity across brains - interpersonal neural synchrony (INS) - is emerging as a powerful marker of social interaction that predicts success of multi-person coordination, communication, and cooperation. As the origins of INS are poorly understood, we tested whether and how INS might emerge from spontaneous dyadic behavior. We recorded neural activity (EEG) and human behavior (full-body kinematics, eye movements and facial expressions) while dyads of participants were instructed to look at each other without speaking or making co-verbal gestures. We made four fundamental observations. First, despite the absence of a structured social task, INS emerged spontaneously only when participants were able to see each other. Second, we show that such spontaneous INS, comprising specific spectral and topographic profiles, did not merely reflect intra-personal modulations of neural activity, but it rather reflected real-time and dyad-specific coupling of neural activities. Third, using state-of-art video-image processing and deep learning, we extracted the temporal unfolding of three notable social behavioral cues - body movement, eye contact, and smiling - and demonstrated that these behaviors also spontaneously synchronized within dyads. Fourth, we probed the correlates of INS in such synchronized social behaviors. Using cross-correlation and Granger causality analyses, we show that synchronized social behaviors anticipate and in fact Granger cause INS. These results provide proof-of-concept evidence for studying interpersonal neural and behavioral synchrony under natural and unconstrained conditions. Most importantly, the results suggest that INS could be conceptualized as an emergent property of two coupled neural systems: an entrainment phenomenon, promoted by real-time dyadic behavior.
... Experiment 1 examined the validity of the rocking chair paradigm for the study of intentional coordination by having participants coordinate rocking chairs inphase (φ = 0˚) or antiphase (φ = 180˚) under three different magnitudes of detuning (∆ω). It was expected that the patterns of interpersonal coordination would be consistent with a coupled oscillator dynamic, such that: (1) inphase would be more stable (less variable) than antiphase; (2) ∆ω ≠ 0 would result in a phase shift that would be (3) more pronounced for antiphase than for inphase, and (4) the variability of relative phase would be greater for ∆ω ≠ 0 than for ∆ω = 0 (Schmidt & Turvey, 1994;Schmidt et al., 1998). ...
... Overall, the results are consistent with previous research using a wristpendulum paradigm to study interpersonal coordination (Schmidt & Turvey, 1994, Schmidt & O'Brien, 1997Schmidt et al., 1998) and provide further evi- dence that such coordination is constrained in accordance with a coupled oscillator dynamic. Moreover, the data establish the efficacy and ecological validity of the rocking chair paradigm for the study of interpersonal coordination. ...
... The behavioral characteristics of leaders and followers in such joint motor actions may manifest in task-specific ways. In some movement tasks, the leader temporally leads the actions, while the follower lags behind [5][6][7][8][9][10] . In other tasks, the leader may exhibit less movement variability to increase the predictability of their actions for the follower 11,12 when the follower was explicitly tasked to coordinate with the movement of the assigned leader. ...
... Following a systematic exploration of the solution space, the experimental conditions characterized by haptic feedback (S400 and S200) led dyads to co-adapt and converge to similar solutions whereby one of the agents' (left) movement spatio-temporally led the other agent's (right) movement (Fig. 3). These asymmetrical contributions suggest that role specialization occurred where the left agent assumed the leader's role according to the common lead-lag definition of leaders in joint motor tasks [5][6][7][8] . Moreover, the left agent also exerted greater force and exhibited more corrective forces than the right agent (Fig. 4), which is consistent with the force-based role specialization found in some of the previous studies 9, 13,14 . ...
Are leaders made or born? Leader–follower roles have been well characterized in social science, but they remain somewhat obscure in sensory-motor coordination. Furthermore, it is unknown how and why leader–follower relationships are acquired, including innate versus acquired controversies. We developed a novel asymmetrical coordination task in which two participants (dyad) need to collaborate in transporting a simulated beam while maintaining its horizontal attitude. This experimental paradigm was implemented by twin robotic manipulanda, simulated beam dynamics, haptic interactions, and a projection screen. Clear leader–follower relationships were learned only when strong haptic feedback was introduced. This phenomenon occurred despite participants not being informed that they were interacting with each other and the large number of equally-valid alternative dyadic coordination strategies. We demonstrate the emergence of consistent leader–follower relationships in sensory-motor coordination, and further show that haptic interaction is essential for dyadic co-adaptation. These results provide insights into neural mechanisms responsible for the formation of leader–follower relationships in our society.
... Research on collective tasks showed that when sharing visual information on their performance, group members tend to coordinate their forces and movements [36,39,40]. Hence, the visual feedback could have an impact on the muscular effort variability between dyads, as well as between participants within each dyad. ...
Team lifting is a complex and collective motor task comprising motor and cognitive components. The purpose of this research is to investigate how individual and collective performances are impacted during load transport combined with a cognitive task. Ten dyads performed a first condition in which they transported a load (CC), and a second one in which they transported the load while maintaining a ball on its top (PC). The recovery-rate, amplitude and period of the centre-of-mass (COM) trajectory were computed for the system (dyad + table = PACS). We analysed the forces and moments exerted at each joint of the upper limbs of the participants. We observed a decrease in the overall performance of the dyads during PC: (i) the velocity and amplitude of CoMPACS decreased by 1.7% and 5.8%, respectively, (ii) inter-participant variability of the Moment-Cost-Function and recovery rate decreased by 95%, and 19.2%, respectively during PC. Kinetic synergy analysis showed that the participants reorganized their coordination in the PC. We demonstrated that adding a precision task affects the economy of collective load carriage at the PACS level while the upper-limbs joint moments were better balanced across the paired participants for the PC.
... Phase synchrony, then, represents the relation between phase angles of two oscillating systems that are coupled. In the case of interpersonal synchrony, coupling refers to an interdependent relationship facilitated through a shared visual or auditory space (Oullier et al., 2008;Schmidt et al., 1998). It has been shown that once in action, coupled systems stabilize to either an in-phase (same phase angle) or anti-phase (opposite angles, e.g., 0° and 180°) angle, and remain in this state robustly (Schmidt et al., 1990). ...
Interpersonal synchrony serves as a subtle, yet powerful bonding mechanism in social interactions. Problematically, the term ‘synchrony’ has been used to label a variety of distinct aspects of interpersonal coordination, such as postural similarities or movement activity entrainment. Accordingly, different algorithms have been suggested to quantify interpersonal synchrony. Yet, it remains unknown whether the different measures of synchrony represent correlated features of the same perceivable core phenomenon. The current study addresses this by comparing the suitability of a set of algorithms with respect to their association with observers’ judgments of dyadic synchrony and leader-followership. One-hundred fifteen observers viewed computer animations of characters portraying the movements of real dyads who performed a repetitive motor task with instruction to move in unison. Animations were based on full-body motion capture data synchronously collected for both partners during the joint exercise. Results showed most synchrony measures significantly correlated with (a) perceived synchrony and (b) the perceived level of balance of leading/following by each dyad member. Phase synchrony and Pearson correlations were associated most strongly with the observer ratings. This might be typical for intentional, structured forms synchrony such as ritualized group activities. It remains open if these findings also apply to spontaneous forms of synchrony as, for instance, occurring in free-running conversations.
... According to della Gatta et al., this suggests that participants represented the joint goal (drawing a circle and a line) motorically, almost as if they were performing the two actions with their own two hands. Thus, the intrapersonal motor coupling typically observed in bimanual coordination (Franz et al., 1991) emerged here in form of interpersonal coupling (consistent with the account that coordination within and between individuals relies on similar processes (e.g., Fine & Amazeen, 2011;Richardson et al., 2007;Schmidt et al., 1998;Schmidt & Richardson, 2008)). ...
When acting jointly, individuals often attend and respond to the same object or spatial location in complementary ways (e.g., when passing a mug, one person grasps its handle with a precision grip; the other receives it with a whole-hand grip). At the same time, the spatial relation between individuals’ actions affects attentional orienting: one is slower to attend and respond to locations another person previously acted upon than to alternate locations (“social inhibition of return”, aka social IOR). Achieving joint goals (e.g., passing a mug), however, often requires complementary return responses to a co-actor’s previous location. This raises the question of whether attentional orienting, and hence the social IOR, is affected by the (joint) goal our actions are directed at. The present study addresses this question. Participants responded to cued locations on a computer screen, taking turns with a virtual co-actor. They pursued either an individual goal or performed complementary actions with the co-actor, in pursuit of a joint goal. Four experiments showed that the social IOR was significantly modulated when participant and co-actor pursued a joint goal. This suggests that attentional orienting is affected not only by the spatial but also by the social relation between two agents’ actions. Our findings thus extend research on interpersonal perception-action effects, showing that the way another agent’s perceived action shapes our own depends on whether we share a joint goal with that agent.
... It has been often observed that leaderfollower relations can emerge even when in absence of a priori role assignment [5][6][7] , which may manifest in task-specific ways. In some tasks, the leader temporally leads the actions, while the follower lags behind [8][9][10] . In other tasks, the leader may exhibit more corrective behavior and variability [11][12][13][14] . ...
... Moreover, the left agent exerted greater force and exhibited more corrective forces than the right agent (Fig. 4). These asymmetrical contributions are consistent with various notions of role specialization or leader-follower relation in human-human cooperation, e.g., spatial or temporal lead-lag, as well as differences in force contributions or corrective responses [9][10][11][12][13][14][15][16]25 . In contrast, when the haptic feedback was absent, dyads did not exhibit systematic co-adaptation. ...
Are leaders made or born? Leader-follower roles have been well characterized in social science, but they remain somewhat obscure in sensory-motor coordination. Furthermore, it is unknown how and why leader-follower relationships are acquired, including innate versus acquired controversies. We developed a novel asymmetrical coordination task in which two participants (dyad) need to collaborate in transporting a simulated beam while maintaining its horizontal attitude. This experimental paradigm was implemented by twin robotic manipulanda, simulated beam dynamics, haptic interactions, and a projection screen. Clear leader-follower relationships were learned despite participants not being informed that they were interacting with each other, but only when strong haptic feedback was introduced. For the first time, we demonstrate the emergence of consistent leader-follower relationships in sensory-motor coordination, and further show that haptic interaction is essential for dyadic co-adaptation. These results provide insights into neural mechanisms responsible for the formation of leader-follower relationships in our society.
... Previous research on interpersonal interaction involving two central nervous systems (CNSs) has demonstrated its similarities to the interactions between the effectors (e.g., fingers) controlled by a single CNS (1,2). For example, Schmidt and colleagues showed that coworkers who can see each other take on coordination patterns similar to those expected in interlimb coordination in single-person actions in rhythmic movements. ...
... For example, Schmidt and colleagues showed that coworkers who can see each other take on coordination patterns similar to those expected in interlimb coordination in single-person actions in rhythmic movements. Previous studies have suggested that the notion of motor synergies (3) developed for single-person actions may be extended to interpersonal actions (2,(4)(5)(6)(7)(8). However, the neural basis of interpersonal motor synergy (IPMS) requires further investigation. ...
... In the case of interpersonal actions, due to the absence of a shared neural controller between coworkers, distributed processes coupled through auditory, visual, and mechanical haptic linkages between coworkers could be responsible for the formation of synergistic interpersonal interactions (1,2,8,(16)(17)(18)(19), namely, interpersonal motor synergy (IPMS). In this work, we define IPMS as the interaction between the efforts (e.g., forces) of two or more individuals, leading to the task-specific enhancement of motor performance. ...
We investigated the role of task constraints on inter-personal interactions. Twenty-one pairs of co-workers performed a finger force production task on force sensors placed at two ends of a seesaw-like apparatus and matched a combined target force of 20N for 23 seconds over ten trials. There were two experimental conditions: 1) FIXED: the seesaw apparatus was mechanically held in place so that the only task constraint was to match the 20N resultant force, and 2) MOVING: the lever in the apparatus was allowed to rotate freely around its fulcrum, acting like a seesaw, so an additional task constraint to (implicitly) balance the resultant moment was added. We hypothesized that the additional task constraint of moment stabilization imposed on the MOVING condition would deteriorate task performance compared to the FIXED condition; however, this was rejected as the performance of the force matching task was similar between two conditions. We also hypothesized that the central nervous systems (CNSs) would employ distinct co-working strategies or inter-personal motor synergy (IPMS) between conditions to satisfy different task constraints, which was supported by our results. Negative covariance between co-worker's forces in the FIXED condition suggested a force stabilization strategy, while positive covariance in the MOVING condition suggested a moment stabilization strategy, implying that independent CNSs adopt distinct IPMSs depending on task constraints. We speculate that, in the absence of a central neural controller, shared visual and mechanical connections between co-workers may suffice to trigger modulations in the cerebellum of each CNS to satisfy competing task constraints.
... Subsequently, the hypothesis of perceptual coupling was supported by investigation of a version of the task in which the coordination was between the oscillating limbs of two different people who coordinated their respective movements by looking at one another (Schmidt et al. 1990). The various phenomena exhibited in the original bimanual coordination studies were replicated in this and subsequent "between people" coordination studies (Schmidt et al. 1998;Amazeen et al. 1995;Schmidt and Turvey 1994;Richardson et al. 2007;de Rugy et al. 2006;Temprado et al. 2003;Temprado and Laurent 2004;Black et al. 2007) as well as studies in which a participant coordinated limb oscillations with a computer-controlled oscillator (Wimmers et al. 1992;Wilson et al. 2010a, b;Snapp-Childs et al. 2011;Coats et al. 2014). The coupling entails visual information in all of these latter studies. ...
... The coupling between two coordinated oscillators is mediated by perception, as demonstrated by the replication of the coordination phenomena exhibited by bimanual coordination in between person coordination (Schmidt et al. 1990(Schmidt et al. , 1998Amazeen et al. 1995;Schmidt and Turvey 1994;Richardson et al. 2007;de Rugy et al. 2006;Temprado et al. 2003;Temprado and Laurent 2004;Black et al. 2007) and personto-computer coordination (Wimmers et al. 1992;Wilson et al. 2010a, b;Snapp-Childs et al. 2011;Coats et al. 2014). The HKB model did not include perceptual information variables. ...
Two rhythmic coordinations, 0° and 180° relative phase, can be performed stably at preferred frequency (~ 1 Hz) without training. Evidence indicates that both 0° and 180° coordination entail detection of the relative direction of movement. At higher frequencies, this yields instability of 180° and spontaneous transition to 0°. The ability to perform a 90° coordination can be acquired by learning to detect and use relative position as information. We now investigate the skilled performance of 90° bimanual coordination with frequency scaling and whether 90° coordination exhibits mode switching to 0° or 180° at higher frequencies. Unlike the switching from 180° to 0°, a transition from the learned 90° coordination to the intrinsic 0° or 180° modes would entail a change in information. This would seem to require intentional decisions during performance as would correcting performance that had strayed from 90°. Relatedly, correction would seem to be an intrinsic part of the performance of 90° during learning. We investigated whether it remains so. We tested bimanual coordination at 90° under both noninterference and correcting instructions. Under correcting instructions, bimanual 90° coordination remained stable at both low and high frequencies. Noninterference instructions yielded stable performance at lower frequencies and switching to 0° or 180° at higher frequencies. Thus, correction is optional and switching to the intrinsic modes occurred. We extended the Bingham (Ecol Psychol 16:45–53, 2004a; Advances in psychology, vol. 135, Time-to-contact, Elsevier Science Publishers, 2004b) model for 0° and 180° coordination to create a dynamical, perception–action account of learned 90° bimanual coordination, in which mode switching and correction were both initiated as the information required for performance of 90° fell below threshold. This means that intentional decisions about what coordination to perform and whether to correct occurred only before performance was begun, not during performance. The extended strictly dynamical model was successfully used to simulate performance of participants in the experiments.
