Tehran J. Davis

Tuning in to another person's action capabilities: perceiving maximal jumping-reach height from walking kinematics.

Three experiments investigated the ability to perceive the maximum height to which another actor could jump to reach an object. Experiment 1 determined the accuracy of estimates for another actors maximal reach-with-jump height and compared these estimates to estimates of the actors standing maximal reaching height and to estimates of the perceivers own maximal reaching and reach-with-jump height. Perception of another actors maximum reach-with-jump height was less accurate than the other estimates, but still accurate to within 8% error. The actors reach-with-jump height was modified in Experiment 2 by attaching weights around the actors ankles. Perceivers, who were explicitly aware of the manipulation, adjusted their maximum reach-with-jump estimates for the actor accordingly. In Experiment 3, perceivers were not explicitly aware of the weight manipulation, but provided significantly lower maximum reach-with-jump estimates after watching the actor walk while wearing the weights compared to estimates obtained after watching the actor walk while not wearing the weights. The results suggest that the actors walking pattern was informative about the actors capacity to produce a different action, jumping to reach an object.

Joint action in a cooperative precision task: nested processes of intrapersonal and interpersonal coordination

The authors determined the effects of changes in task demands on interpersonal and intrapersonal coordination. Participants performed a joint task in which one participant held a stick to which a circle was attached at the top (holding role), while the other held a pointer through the circle without touching its borders (pointing role). Experiment 1 investigated whether interpersonal and intrapersonal coordination varied depending on task difficulty. Results showed that interpersonal and intrapersonal coordination increased in degree and stability with increments in task difficulty. Experiment 2 explored the effects of individual constraints by increasing the balance demands of the task (one or both members of the pair stood in a less stable tandem stance). Results showed that interpersonal coordination increased in degree and stability as joint task demands increased and that coupling strength varied depending on joint and individual task constraints. In all, results suggest that interpersonal and intrapersonal coordination are affected by the nature of the task performed and the constraints it places on joint and individual performance.

Carrying the height of the world on your ankles: Encumbering observers reduces estimates of how high an actor can jump

The authors investigated how changes in action capabilities affect estimation of affordances for another actor. Observers estimated maximum jumping-reach height for themselves and another actor. Half of the observers wore ankle weights that reduced their jumping ability. The ankle weights reduced estimates of maximum jumping-reach height that observers made for themselves and for the other actor, but only after observers had the opportunity to walk while wearing the weights. Changes in estimates closely matched changes in actual jumping-reach ability. Results confirm and extend recent investigations that indicate that perception of the spatial layout of surfaces in the environment is scaled to an observers capacity to act, and they link that approach to another embodied cognition perspective that posits a link between ones own action capabilities and perception of the actions of other agents.

Perceiving action boundaries: Learning effects in perceiving maximum jumping-reach affordances

Coordinating with another person requires that one can perceive what the other is capable of doing. This ability often benefits from opportunities to practice and learn. Two experiments were conducted in which we investigated perceptual learning in the context of perceiving the maximum height to which an actor could jump to reach an object. Those estimates were compared with estimates that perceivers made for themselves. In Experiment 1, participants initially underestimated the maximum jumping-reach height both for themselves and for the actor. Over time, without explicit feedback, the participants were able to improve estimates of their own maximum jumping-reach height, but estimates for the actor did not improve. In Experiment 2, participants observed the actor perform either an action related but nonidentical to jumping (lifting a weight by squatting) or a nonrelated activity (rotating the torso). The participants who observed the actor perform the related action were able to improve the accuracy of their perceptual reports for the actor’s maximum jumping-reach height, but the participants who watched the actor perform the nonrelated task were unable to do so. The results indicate some degree of independence between perceived affordances for the self and others, suggesting that affordance judgments are not entirely dependent on or determined by characteristics of the perceiver.

Visual influences on postural and manual interpersonal coordination during a joint precision task

Abstract We investigated whether the interpersonal postural coordination that occurs during a joint supra-postural, manual precision task is driven by the constraints of the task, or, instead results from visual entrainment to the movements of a co-actor. Participants were instructed to coordinate their finger movements under conditions where participants could see others’ whole-body movements or could only see the results of the other’s actions. Participants’ finger and torso movements were recorded. Coordination was quantified using cross-recurrence quantification analysis measures. Interpersonal coordination was enhanced by, although it did not depend entirely upon, visual information about the co-actor’s body movements.

Multi-scale interactions in interpersonal coordination

Background Interpersonal coordination is an essential aspect of daily life, and crucial to performance in cooperative and competitive team sports. While empirical research has investigated interpersonal coordination using a wide variety of analytical tools and frameworks, to date very few studies have employed multifractal techniques to study the nature of interpersonal coordination across multiple spatiotemporal scales. In the present study we address this gap. Methods We investigated the dynamics of a simple dyadic interpersonal coordination task where each participant manually controlled a virtual object in relation to that of his or her partner. We tested whether the resulting hand-movement time series exhibits multi-scale properties and whether those properties are associated with successful performance. Results Using the formalism of multifractals, we show that the performance on the coordination task is strongly multi-scale, and that the multi-scale properties appear to arise from interaction-dominant dynamics. Further, we find that the measure of across-scale interactions, multifractal spectrum width, predicts successful performance at the level of the dyad. Conclusion The results are discussed with respect to the implications of multifractals and interaction-dominance for understanding control in an interpersonal context.

Spontaneous Interentity Coordination in a Dissipative Structure

ABSTRACT Humans and other creatures display remarkable interorganism coordination. For ecological theorists, interorganism coordination poses a challenge because it appears to be an especially “representation-hungry” phenomenon (Clark, 1999). Ecological researchers have proposed that interorganism coordination arises from fundamental laws of pattern formation and synchronization. A key example in support of the ecological approach to coordination is the phase locking of 2 or more weakly coupled metronomes. Here we provide a complementary example of interentity coordination in a system that is more closely analogous to living systems. We show that two self-organizing dissipative structures, coupled in a single electrical field, spontaneously exhibit fairly complex motion coordination. Further, the degree of coordination predicts the rate of entropy production for the system as a whole. We suggest that the complex behavior of motion coordination fulfills a rudimentary end-directedness of the system: evolve to states that create higher rates of entropy production.

The Stance Leads the Dance: The Emergence of Role in a Joint Supra-Postural Task

Successfully meeting a shared goal usually requires co-actors to adopt complementary roles. However, in many cases, who adopts what role is not explicitly predetermined, but instead emerges as a consequence of the differences in the individual abilities and constraints imposed upon each actor. Perhaps the most basic of roles are leader and follower. Here, we investigated the emergence of “leader-follower” dynamics in inter-personal coordination using a joint supra-postural task paradigm (Ramenzoni et al., 2011; Athreya et al., 2014). Pairs of actors were tasked with holding two objects in alignment (each actor manually controlled one of the objects) as they faced different demands for stance (stable vs. difficult) and control (which actor controlled the larger or smaller object). Our results indicate that when actors were in identical stances, neither led the inter-personal (between actors) coordination by any systematic fashion. Alternatively, when asymmetries in postural demands were introduced, the actor with the more difficult stance led the coordination (as determined using cross-recurrence quantification analysis). Moreover, changes in individual stance difficulty resulted in similar changes in the structure of both intra-personal (individual) and inter-personal (dyadic) coordination, suggesting a scale invariance of the task dynamics. Implications for the study of interpersonal coordination are discussed.

A cluster phase analysis for collective behavior in team sports

Collective behavior can be defined as the ability of humans to coordinate with others through a complex environment. Sports offer exquisite examples of this dynamic interplay, requiring decision making and other perceptual-cognitive skills to adjust individual decisions to the team self-organization and vice versa. Considering players of a team as periodic phase oscillators, synchrony analyses can be used to model the coordination of a team. Nonetheless, a main limitation of current models is that collective behavior is context independent. In other words, players on a team can be highly synchronized without this corresponding to a meaningful coordination dynamics relevant to the context of the game. Considering these issues, the aim of this study was to develop a method of analysis sensitive to the context for evidence-based measures of collective behavior.

End-Directedness and Context in Nonliving Dissipative Systems

The extensive study of thermodynamically open, non-equilibrium systems in the context of self-organization has revealed that biological phenomena such as clocking, pattern formation, and chemotaxis may also be found more generally in non-living (e.g., chemical) systems. We show that another fundamental biological phenomenon, end-directedness, also appears in non-living systems. We present a non-living dissipative system that exhibits end-directed processes in seeking and drawing the energy needed to form and maintain its structure. The system can become sensitive to its context, defined as gradients other than its primary energy source, and use context to coordinate with its environment. Implications for biological systems will be discussed.