R. C. Schmidt

Phase transitions and critical fluctuations in the visual coordination of rhythmic movements between people

By watching each others lower oscillating leg, 2 seated Ss kept a common tempo and a particular phase relation of either 0 degrees (symmetric mode) or 180 degrees (alternate mode). This study investigated the differential stability of the 2 phase modes. In Experiment 1, in which Ss were instructed to remain in the initial phase mode, the alternate phase mode was found to be less stable as the frequency of oscillation increased. In addition, analysis of the nonsteady state cycles revealed evidence of a switching to the symmetric phase mode for the initial alternate phase mode trials. In Experiments 2 and 3, Ss were instructed to remain at a noninitial phase angle if it was found to be more comfortable. The transition observed between the 2 phase modes satisfies the criteria of a physical bifurcation--hysteresis, critical fluctuations, and divergence--and is consonant with previous findings on transitions in limb coordination within a person.

Social Connection Through Joint Action and Interpersonal Coordination

The pull to coordinate with other individuals is fundamental, serving as the basis for our social connectedness to others. Discussed is a dynamical and ecological perspective to joint action, an approach that embeds the individuals mind in a body and the body in a niche, a physical and social environment. Research on uninstructed coordination of simple incidental rhythmic movement, along with research on goal-directed, embodied cooperation, is reviewed. Finally, recent research is discussed that extends the coordination and cooperation studies, examining how synchronizing with another, and how emergent social units of perceiving and acting are reflected in peoples feelings of connection to others.

Effects of Visual and Verbal Interaction on Unintentional Interpersonal Coordination.

Previous research has demonstrated that peoples movements can become unintentionally coordinated during interpersonal interaction. The current study sought to uncover the degree to which visual and verbal (conversation) interaction constrains and organizes the rhythmic limb movements of coactors. Two experiments were conducted in which pairs of participants completed an interpersonal puzzle task while swinging handheld pendulums with instructions that minimized intentional coordination but facilitated either visual or verbal interaction. Cross-spectral analysis revealed a higher degree of coordination for conditions in which the pairs were visually coupled. In contrast, verbal interaction alone was not found to provide a sufficient medium for unintentional coordination to occur, nor did it enhance the unintentional coordination that emerged during visual interaction. The results raise questions concerning differences between visual and verbal informational linkages during interaction and how these differences may affect interpersonal movement production and its coordination.

Dynamics of Interpersonal Coordination

Everyday human actions often occur in a social context. Past psychological research has found that the motor behavior of socially situated individuals tends to be coordinated. Our research performed over the last 20 years has sought to understand how the mutuality, accommodation, and synchrony found in everyday interactional coordination can be understood using a dynamical theory of behavioral order, namely coordination dynamics. Using laboratory interpersonal tasks, we have demonstrated that when two people are asked to rhythmically coordinate their limbs they show behavioral phenomena identical to those found in bimanual interlimb coordination, which has been mathematically modeled as a dynamical process. Research has demonstrated that these same dynamical organizing principles can coordinate the rhythmic movements of two people unintentionally and that the weaker, intermittent coordination that ensues is affected by both perceptual (e.g., attentional focus and information pickup activity of the visual system) and dynamical constraints (e.g., intrapersonal rhythmic synergies and period basin of entrainment). Other research has investigated how traditional social and personality properties of a dyad (rapport, social competence) relate to dynamical properties of a dyad’s coordinated movements and how the stability of coordinated movements mirrors the stability of mental connectedness experienced in social interactions.

Contrasting Approaches to Perceiving and Acting With Others

How and why the presence of a person directly affects the perception and action of another person is a phenomenon that has been approached in a limited and piecemeal fashion within psychology. This kind of diffuse strategy has failed to capture the jointness of perception and action within and between people. In contradistinction, the authors offer a perspective that retains both integrally social features (e.g., involves interaction) and yet adequately exploits the current state of knowledge regarding the ecological properties of perception–action, while at the same time drawing on aspects of dynamic systems theory. In this article the authors review the best attempts to examine how one individual affects anothers perceptions and actions in the emergence of a social unit of action. Two important approaches, the individual-level and cognitive dynamics approaches, have yielded insights that derive in significant degree from principles of ecological psychology and/or dynamical systems theory. Prototypic of the individual-level approach is a focus on what can be perceived by coactors with the aim of uncovering how the dispositional qualities (affordances) of another person are informationally specified during social interaction. In contrast, the cognitive dynamics approach simulates dynamical characteristics of cognition and psychological influence with the aim of uncovering how cooperative interaction emerges out of its component parts. The authors argue that these approaches involve, respectively, insufficient mutuality and insufficient embodiment. Consequently, a social synergy perspective is discussed that approaches the problem of socially cooperative interaction at the relational, nonreductive level, using novel methods to examine how social perception and action emerge through self-organizing processes. The coupling of Gibsons ideas with those of Bernstein forms a natural basis for looking at the traditional psychological topics of perceiving, acting, and knowing as activities of ecosystems rather than isolated animals. (Shaw, Mace, & Turvey, 2001, p. xiv)

A Comparison of Intra- and Interpersonal Interlimb Coordination: Coordination Breakdowns and Coupling Strength

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 difference in the eigenfrequencies (preferred tempos) of the individual oscillating limbs. The properties observed for both intra- and interpersonal coordination were those predicted by a dynamical model of rhythmic coordination that considers the coordinated limbs coupled to be nonlinear oscillators. Using a regression method, the coupling strengths of the coupled system were recovered. As predicted by the dynamical model, the strength of the dynamic was generally greater for the in-phase than the anti-phase mode and decreased with increasing frequency. Further, the strength of the interpersonal interlimb coupling was weaker than that of intrapersonal interlimb coupling.

Coupling dynamics in interlimb coordination

In 1:1 frequency locking, the interlimb phase difference phi is an order parameter quantifying the spatial-temporal organization of 2 rhythmic subsystems. Dynamical modeling and experimental analyses indicate that an intentional parameter phi psi (intended coordination mode, phi = 0 degrees or phi = 180 degrees) and 2 control parameters omega c (coupled frequency) and delta omega (difference between uncoupled eigen-frequencies) affect phi. An experiment was conducted on 1:1 frequency locking in which phi psi, omega c, and delta omega were manipulated using a paradigm in which a person swings hand-held pendulums. As delta omega deviated from 0, the observed phi deviated from the phi psi, indicating a displacement in the phi attractor point. The displacements were exaggerated by increasing omega c. The displacements were coordinated with a decrease in the stability of phi and with higher harmonics in power spectrum of phi. Implications of the results for modeling interlimb coordination are discussed.

Phase-entrainment dynamics of visually coupled rhythmic movements

Do interlimb rhythmic coordinations between individuals exhibit the same relations among the same observable quantities as interlimb rhythmic coordination within an individual? The 1∶1 frequency locking between the limbs of two people was investigated using a paradigm in which each person oscillated a hand-held pendulum, achieving and maintaining the mutual entrainment through vision. The intended coordination was antiphase, φ=π, and the difference between the uncoupled eigenfrequencies, Δω, was manipulated through differences in the lengths of the two pendulums. The mean phase relation and its variance for visually coupled coordinations differing in Δω were predicted by an order parameter equation developed by Haken et al. (1985) and Schöner et al. (1986) for the relative phase of correlated movements of limb segments. Specifically, the experiment revealed that: (1) the deviation of φ from π increased with increasing deviation of Δω from 0; and (2) fluctuations in φ increased with increasing deviation of Δω from 0. With deviations of Δω from 0, new peaks were added at higher harmonics in φs power spectrum. These results were in agreement with previous research on the stable states of interlimb coordination within a person, mediated by mechanoreceptive rather than photoreceptive mechanisms. Additionally, they were in agreement with previous research on phase transitions in interlimb coordination which have been shown to conform to the same order parameter dynamics whether the coupling be mechanoreceptively or photoreceptively based. It was suggested that phase entrainment in biological movement systems may abide by dynamical principles that are indifferent to the details of the coupling.

Hefting for a Maximum Distance Throw: A Smart Perceptual Mechanism*

Objects for throwing to a maximum distance were selected by hefting objects varying in size and weight. Preferred weights increased with size reproducing size-weight illusion scaling between weight and volume. In maximum distance throws, preferred objects were thrown the farthest. Throwing was related to hefting as a smart perceptual mechanism. Two strategies for conveying high kinetic energy to projectiles were investigated by studying the kinematics of hefting light, preferred, and heavy objects. Changes in tendon lengths occurring when objects of varying size were grasped corresponded to changes in stiffness at the wrist. Hefting with preferred objects produced an invariant phase between the wrist and elbow. This result corresponded to an optimal relation at peak kinetic energy for the hefting. A paradigm for the study of perceptual properties was compared to size-weight illusion methodology.

Frequency detuning of the phase entrainment dynamics of visually coupled rhythmic movements

An order parameter equation for correlated limb movements was applied to rhythmic coordination between the limbs of two people. The interlimb coordination was established and maintained through vision. Manipulations of frequency competition, coupled frequency, and intended mode (in-phase or anti-phase) produced equilibria and fluctuations in relative phase predicted by the order parameter equation and confirmed originally in within-person coordination. It was concluded that there is an elementary coordination dynamics governing the rhythmic coordination between organisms as well as between components of a single organism.