Individual contributions to (re-)stabilizing interpersonal movement coordination

Interpersonal Synchronization Processes in Discrete and Continuous Tasks

Three frameworks have been proposed to account for interpersonal synchronization: The information processing approach argues that synchronization is achieved by mutual adaptation, the coordination dynamics perspective supposes a continuous coupling between systems, and complexity matching suggests a global, multi-scale interaction. We hypothesized that the relevancy of these models was related to the nature of the performed tasks. 10 dyads performed synchronized tapping and synchronized forearm oscillations, in two conditions: full (participants had full information about their partner), and digital (information was limited to discrete auditory signals). Results shows that whatever the task and the available information, synchronization was dominated by a discrete mutual adaptation. These results question the relevancy of the coordination dynamics perspective in interpersonal coordination.

Accessing interpersonal and intrapersonal coordination dynamics

Both intrapersonal and interpersonal coordination dynamics have traditionally been investigated using relative phase patterns of in-phase (ϕ = 0°) and/or anti-phase (ϕ = 180°). Numerous investigations have demonstrated that coordination tasks that require other relative phase patterns (e.g., 90°) are difficult or near impossible to perform without extended practice. Recent findings, however, have demonstrated that an individual can produce a wide range of intrapersonal bimanual patterns within a few minutes of practice when provided integrated feedback. The present experiment was designed to directly compare intra- and interpersonal coordination performance and variability when provided Lissajous feedback or pacing metronome. Single participants (N = 12) and pairs of participants (N = 24, 12 pairs) were required to produce relative phase patterns between 0° and 180° in 30° increments using either pacing metronomes or Lissajous displays. The Lissajous displays involved a goal template and a cursor providing integrated feedback regarding the position of the two effectors. The results indicated both single and pairs of participants could effectively produce a large range of coordination patterns that typically act as repellers after only 6 min of practice when provided integrated feedback. However, single participants performed the in-phase coordination pattern more accurately and with less variability than paired participants, regardless of the feedback condition. These results suggest an advantage for intrapersonal coordination when performing in-phase coordination, possibly due to the stabilizing effect occurring via the neuro-muscular linkage between effectors.

How Interpersonal Coordination Affects Individual Behavior (and Vice Versa): Experimental analysis and adaptive HKB model of social memory

How one behaves after interacting with a friend may not be the same as before the interaction. The present study investigated which spontaneous coordination patterns formed between two persons and whether a remnant of the interaction remained ("social memory"). Pairs of people sat face-to-face and continuously flexed index fingers while vision between partners was manipulated to allow or prevent information exchange. Trials consisted of three successive twenty-second intervals: without vision, with vision, and again without vision. Steady, transient, or absent phase coupling was observed during vision. In support of social memory, participants tended to remain near each other's movement frequency after the interaction ended. Furthermore, the greater the stability of interpersonal coordination, the more similar partners' post-interactional frequencies became. Proposing that social memory resulted from prior frequency adaptation, a model based on Haken-Kelso-Bunz oscillators reproduced the experimental findings, even for patterns observed on individual trials. Parametric manipulations revealed multiple routes to social memory through the interplay of adaptation and other model parameters. The experimental results, model, and interpretation motivate potential future research and therapeutic applications.

Individual and dyadic rope turning as a window into social coordination

The spontaneous and intentional movement coordination between peoples is well understood. Less is known about such interactions when the coordination is subordinate to the task and when the task involves, next to vision, mechanically induced haptic and kinesthetic coupling between dyadic partners. We therefore investigated dyadic jump rope turning. Fifteen dyadic pairs conjointly turned a jump rope to which five markers were equidistantly attached, and whose movements were recorded in 3D. In addition, each participant turned one side of the rope while the other side was quasi-fixed in an individual baseline condition. The participants' goal was to turn the rope regularly and smoothly. Individual spontaneous turning frequencies differed substantially across participants. Yet, dyadic pairs spontaneously turned the rope at a common frequency, indicative of frequency entrainment. The dyadic rope rotations were less variable despite weaker between near-hand marker coordination than the individual rope rotations, and the degree of performance improvement was most pronounced for participants who were paired with a partner who performed better in the individual condition. The direction and relative strength of the coupling between partners varied substantially across dyads, but the degree of coupling asymmetry had no substantial effect on the rope tuning quality. The absolute degree in which dyadic partners adjusted to each other, however, scaled moderately with their turning performance. Although the individual performances did not predict the dyadic performances, the difference in individual performance between dyadic partners had some predictive value for the dyadic performance. In combination, these results indicate that the partners were functionally adapting to each other in order to satisfy the task goal and suggest that the relative performance differences rather than the individual performances has predictive value for conjoint action.

Autism in Action: Reduced Bodily Connectedness during Social Interactions?

Autism is a lifelong disorder, defined by deficits in social interactions and flexibility. To date, diagnostic markers for autism primarily include limitations in social behavior and cognition. However, such tests have often shown to be inadequate for individuals with autism who are either more cognitively able or intellectually disabled. The assessment of the social limitations of autism would benefit from new tests that capture the dynamics of social initiative and reciprocity in interaction processes, and that are not dependent on intellectual or verbal skills. New entry points for the development of such assessments may be found in ‘bodily connectedness’, the attunement of bodily movement between two individuals. In typical development, bodily connectedness is related to psychological connectedness, including social skills and relation quality. Limitations in bodily connectedness could be a central mechanism underlying the social impairment in autism. While bodily connectedness can be minutely assessed with advanced techniques, our understanding of these skills in autism is limited. This Perspective provides examples of how the potential relation between bodily connectedness and specific characteristics of autism can be examined using methods from the coordination dynamics approach. Uncovering this relation is particularly important for developing sensitive tools to assess the tendency to initiate social interactions and the dynamics of mutual adjustments during social interactions, as current assessments are not suited to grasp ongoing dynamics and reciprocity in behavior. The outcomes of such research may yield valuable openings for the development of diagnostic markers for autism that can be applied across the lifespan.

Does interpersonal movement synchronization differ from synchronization with a moving object?

We examined whether movement synchronization is different during coordination with another person than during coordination with a moving object. In addition, the influence of belief in the other person's agency was assessed. Participants synchronized their lower-arm movements with a computer-controlled rhythmic reference movement. The reference movements were pre-recorded, biological movements and were identical in all conditions. They were presented either by means of a confederate's arm in a motor-driven manipulandum or by means of movements of the manipulandum alone. To assess the influence of the belief in the confederate's agency, participants either were or were not informed that the confederate's movements were motor driven. The strength of coupling between the participant's movements and the reference movements was assessed in terms of the standard deviation of relative phase and the time needed to re-establish the coordination pattern after an unexpected perturbation of the reference signal. Mean relative phase indicated whether the participant was leading or lagging the reference movements. Coupling strength was not affected by the presence of another person in the coordination task, nor by the belief in this person's agency. However, participants had a stronger tendency to lead while synchronizing with the manipulandum, indicating that they responded differently to the observed kinematics of this moving object than to the kinematics of the confederate's arm movements, at least when the confederate's agency was assumed. Hence, although neither the involvement of another person nor the participant's belief in this person's agency affected coupling strength, the form of the coupling seemed to be influenced by the former factor, suggesting a different attunement to the reference movements during a joint-action situation. Future research is required to determine whether these interpretations extend to unintentional and bidirectional coordination, in which agency is not only assumed but actually effectuated.

Asymmetric interpersonal coupling in a cyclic sports-related movement task

In interactive sports, teammates and/or opponents mutually tune their behavior. Expert performance thus implies certain interactive abilities, which critically depend on perceptual coupling. To illustrate this assertion, we examined the coordination dynamics with asymmetric interaction of dyads performing a sports-related cyclical movement task. In pairs, basketball players performed lateral defensive slides in in-phase, until a cue prompted them to switch to antiphase coordination. We assessed how these switches were mediated by phase adaptations of each agent under bidirectional (i.e., agents facing one another) and unidirectional (i.e., one agent facing the back of the other) visual interaction conditions. This imposed asymmetry in visual coupling exemplified an imbalance in the interaction (or 'interact-ability') between two agents. The results concurred the asymmetric coupling: during the switch the agent facing the other adapted his phasing more than the other agent. Furthermore, also in the bidirectional condition the coupling revealed dyad-intrinsic asymmetries (e.g., related to implicit follower-leader strategies). Together, this illustrates that interpersonal coordination is characterized by asymmetric coupling between the agents, and highlights how mutual perception of pertinent information mediates interpersonal coordination. This study offered a first step towards analyzing interpersonal coordination dynamics in relation to 'interact-ability'.