Aligned bodies, united hearts: embodied emotional dynamics of an Islamic ritual

Collective rituals involve the coordination of intentions and actions and have been shown to promote the alignment of emotional states and social identities. However, the mechanics of achieving group-level synchrony is yet unclear. We report the results of a naturalistic study in the context of an Islamic congregational prayer that involves synchronous movement. We used wearable devices to capture data on body posture, autonomic responses and spatial proximity to investigate how postural alignment and shared arousal intertwine during this ritual. The findings reveal a dual process at play: postural alignment appears to be more localized, with worshippers synchronizing their movements with their nearest neighbours, while physiological alignment operates on a broader scale, primarily driven by the central role of the religious leader. Our findings underscore the importance of interpersonal dynamics in collective gatherings and the role of physical co-presence in fostering connections among participants, with implications extending to our understanding of group dynamics across various social settings.This article is part of the theme issue 'Minds in movement: embodied cognition in the age of artificial intelligence'.

Different effects of visual occlusion on interpersonal coordination of head and body movements during dyadic conversations

Introduction

In recent decades, interpersonal coordination and synchrony have been extensively examined in the field of psychology and cognitive science. Studies suggest that perceptual information enables interpersonal coordination and that perceptual noise may even enhance coordination. However, how these perceptual factors influence interpersonal coordination dynamics between head and body movements remains unclear. This study investigated the effect of visual information on the interpersonal coordination of head and body movements during dyadic conversations.

Methods

The availability of visual information was manipulated by positioning a partition halfway between a pair of participants, and the conversations were recorded using a video camera. A video-based human pose estimation software (OpenPose) was used to quantify each interlocutor's head and body movements, which were submitted for cross-recurrence quantification analysis (CRQA), to assess the degree of coordination between the interlocutors.

Results

The results showed different effects between head- and body-movement coordination (i.e., a CRQA measure, maximum line length). The occlusion of visual information increased head-movement coordination, whereas it decreased body-movement coordination.

Discussion

The results suggest that a distinct mechanism may be present at the head- and body-movement coordination level and this study observed differing appearances of compensatory behaviors. Further studies should be conducted to investigate the complex relationships between interpersonal coordination dynamics and various kinds of communication constraints, such as long-term or short-term, and lower-order (perceptual-motor) or higher-order (cognitive-social) level constraints.

Bimanual finger coordination in professional and amateur darbuka players

Professional hand percussionists who play the darbuka (a drum from the Middle East) show fast and stable bimanual finger coordination compared to amateur players. A cross-recurrence quantification analysis clarifies how stable bimanual coordination is achieved by dissociating stochastic noise and attractor strength in the dynamic system. This study employed a cross-recurrence quantification analysis to examine professional and amateur darbuka players' fast and stable bimanual finger coordination. Eight professional and eight amateur percussion players participated in the study and played a darbuka with their right and left ring fingers, alternating as fast as possible for 12 s. We then analyzed the finger position data and calculated the stochastic noise and attractor strength from the density and the longest diagonal line in the recurrence plot, respectively. We used linear mixed-effects models to test whether stochastic noise and attractor strength differed between professional and amateur players. The results indicate that professional darbuka players achieve fast and stable bimanual finger coordination by enhancing attractor strength rather than reducing stochastic noise in the dynamic system.

Stage 2: Visual information and communication context as modulators of interpersonal coordination in face-to-face and videoconference-based interactions

Interpersonal coordination of body movement-or similarity in patterning and timing of body movement between interaction partners-is well documented in face-to-face (FTF) conversation. Here, we investigated the degree to which interpersonal coordination is impacted by the amount of visual information available and the type of interaction conversation partners are having. To do so within a naturalistic context, we took advantage of the increased familiarity with videoconferencing (VC) platforms and with limited visual information in FTF conversation due to the COVID-19 pandemic. Pairs of participants communicated in one of three ways: FTF in a laboratory setting while socially distanced and wearing face masks; VC in a laboratory setting with a view of one another's full movements; or VC in a remote setting with a view of one another's face and shoulders. Each pair held three conversations: affiliative, argumentative, and cooperative task-based. We quantified interpersonal coordination as the relationship between the two participants' overall body movement using nonlinear time series analyses. Coordination changed as a function of the contextual constraints, and these constraints interacted with coordination patterns to affect subjective conversation outcomes. Importantly, we found patterns of results that were distinct from previous research; we hypothesize that these differences may be due to changes in the broader social context from COVID-19. Taken together, our results are consistent with a dynamical systems view of social phenomena, with interpersonal coordination emerging from the interaction between components, constraints, and history of the system.

Does bimanual coordination training benefit inhibitory function in older adults?

Introduction

Whether complex movement training benefits inhibitory functions and transfers the effects to non-practiced motor and cognitive tasks is still unknown. The present experiment addressed this issue using a bimanual coordination paradigm. The main hypothesis was that bimanual coordination training allows for improving the involved cognitive (i.e., inhibition) mechanisms and then, transferring to non-practiced cognitive and motor tasks, that share common processes.

Methods

17 older participants (72.1 ± 4.0 years) underwent 2 training and 3 test sessions (pre, post, and retention one week after) over three weeks. Training included maintaining bimanual coordination anti-phase pattern (AP) at high frequency while inhibiting the in-phase pattern (IP). During the test sessions, participants performed two bimanual coordination tasks and two cognitive tasks involving inhibition mechanisms. Transfer benefits of training on reaction time (RT), and total switching time (TST) were measured. In the cognitive tasks (i.e., the Colour Word Stroop Task (CWST) and the Motor and Perceptual Inhibition Test (MAPIT)), transfer effects were measured on response times and error rates. Repeated one-way measures ANOVAs and mediation analyses were conducted.

Results

Results confirmed that training was effective on the trained task and delayed the spontaneous transition frequency. Moreover, it transferred the benefits to untrained bimanual coordination and cognitive tasks that also involve inhibition functions. Mediation analyses confirmed that the improvement of inhibitory functions mediated the transfer of training in both the motor and cognitive tasks.

Discussion

This study confirmed that bimanual coordination practice can transfer training benefits to non-practiced cognitive and motor tasks since presumably they all share the same cognitive processes.

Say that again: Quantifying patterns of production for children with autism using recurrence analysis

The current research study characterized syntactic productivity across a range of 5-year-old children with autism and explored the degree to which this productivity was associated with standardized measures of language and autism symptomatology. Natural language samples were transcribed from play-based interactions between a clinician and participants with an autism diagnosis. Speech samples were parsed for grammatical morphemes and were used to generate measures of MLU and total number of utterances. We applied categorical recurrence quantification analysis, a technique used to quantify patterns of repetition in behaviors, to the children's noun-related and verb-related speech. Recurrence metrics captured the degree to which children repeated specific lexical/grammatical units (i.e., recurrence rate) and the degree to which children repeated combinations of lexical/grammatical units (i.e., percent determinism). Findings indicated that beyond capturing patterns shown in traditional linguistic analysis, recurrence can reveal differences in the speech productions of children with autism spectrum disorder at the lexical and grammatical levels. We also found that the degree of repeating noun-related units and grammatical units was related to MLU and ADOS Severity Score, while the degree of repeating unit combinations (e.g., saying "the big fluffy dog" or the determiner-adjective-adjective-noun construction multiple times), in general, was only related to MLU.

Visual information and communication context as modulators of interpersonal coordination in face-to-face and videoconference-based interactions

Interpersonal coordination of body movement-or the similarity in patterning and timing of body movement between interaction partners over time-is a well-documented phenomenon in face-to-face (FTF) conversation. The present study will investigate the degree to which interpersonal coordination is impacted by the amount of visual information available and the type of interaction conversation partners are having. To do so within a naturalistic context, we take advantage of changes induced by the 2020 COVID-19 pandemic. The pandemic has changed communication, with mitigation efforts having forced nearly everyone to engage over videoconferencing (VC) platforms (which limit body visibility but not face visibility) or to meet FTF with public health constraints (which limit face visibility but not body visibility). We will ask 69 pairs of participants to communicate in one of three ways: (1) socially distanced FTF while wearing masks; (2) VC in a laboratory where each partner will see one another's full torso; or (3) VC in a remote setting where each partner will see only one another's face and shoulders. Each pair will hold three conversations: (a) affiliative, (b) argumentative, and (c) task-based. We will quantify interpersonal coordination by extracting overall amounts of movement from videos of the participants using well-validated computer vision methods and then calculating the relationship between the two participants' movement using nonlinear time series analyses. In doing so, we will be able to identify the degree to which visual information and conversational context shape the emergence of interpersonal coordination within now-naturalistic modes of interaction.

Bimanual Coordination in a Whole-Body Dynamic Balance Sport, Slacklining: A Comparison of Novice and Expert

As previous studies have suggested that bimanual coordination is important for slacklining, the authors questioned whether this important skill plays a role in the performance of a fundamental task of slacklining. To address this question, the authors compared single-leg standing on the slackline between novices and experts in terms of bimanual coordination dynamics within a dynamical systems framework using relative phase and recurrence quantification analysis measures. Five novices and five experts participated in the experiment. Participants were required to perform single-leg standing on a slackline. To collect motion data while slacklining, the authors used a 3D motion capture system and obtained time series data on the wrist position of both hands. The authors compared bimanual coordination dynamics between novices and experts. Although this preliminary study was limited in its sample size, the results suggest that experts tend to show a more antiphase coordination pattern than novices do and that they can more sustainably coordinate their hands compared with novices in terms of temporal structure in diagonal-related recurrence measures (i.e., maxline, mean line, and percentage determinism).

Gesture-speech physics in fluent speech and rhythmic upper limb movements

It is commonly understood that hand gesture and speech coordination in humans is culturally and cognitively acquired, rather than having a biological basis. Recently, however, the biomechanical physical coupling of arm movements to speech vocalization has been studied in steady-state vocalization and monosyllabic utterances, where forces produced during gesturing are transferred onto the tensioned body, leading to changes in respiratory-related activity and thereby affecting vocalization F0 and intensity. In the current experiment (n = 37), we extend this previous line of work to show that gesture-speech physics also impacts fluent speech. Compared with nonmovement, participants who are producing fluent self-formulated speech while rhythmically moving their limbs demonstrate heightened F0 and amplitude envelope, and such effects are more pronounced for higher-impulse arm versus lower-impulse wrist movement. We replicate that acoustic peaks arise especially during moments of peak impulse (i.e., the beat) of the movement, namely around deceleration phases of the movement. Finally, higher deceleration rates of higher-mass arm movements were related to higher peaks in acoustics. These results confirm a role for physical impulses of gesture affecting the speech system. We discuss the implications of gesture-speech physics for understanding of the emergence of communicative gesture, both ontogenetically and phylogenetically.

An Approach to Aligning Categorical and Continuous Time Series for Studying the Dynamics of Complex Human Behavior

An emerging perspective on human cognition and performance sees it as a kind of self-organizing phenomenon involving dynamic coordination across the body, brain and environment. Measuring this coordination faces a major challenge. Time series obtained from such cognitive, behavioral, and physiological coordination are often complicated in terms of non-stationarity and non-linearity, and in terms of continuous vs. categorical scales. Researchers have proposed several analytical tools and frameworks. One method designed to overcome these complexities is recurrence quantification analysis, developed in the study of non-linear dynamics. It has been applied in various domains, including linguistic (categorical) data or motion (continuous) data. However, most previous studies have applied recurrence methods individually to categorical or continuous data. To understand how complex coordination works, an integration of these types of behavior is needed. We aimed to integrate these methods to investigate the relationship between language (categorical) and motion (continuous) directly. To do so, we added temporal information (a time stamp) to categorical data (i.e., language), and applied joint recurrence analysis methods to visualize and quantify speech-motion coordination coupling during a rap performance. We illustrate how new dynamic methods may capture this coordination in a small case-study design on this expert rap performance. We describe a case study suggesting this kind of dynamic analysis holds promise, and end by discussing the theoretical implications of studying complex performances of this kind as a dynamic, coordinated phenomenon.

Spontaneous bimanual independence during parallel tapping and sawing

The performance of complex polyrhythms-rhythms where the left and right hand move at different rates-is usually the province of highly trained individuals. However, studies in which hand movement is guided haptically show that even novices can perform polyrhythms with no or only brief training. In this study, we investigated whether novices are able to tap with one hand by matching different rates of a metronome while sawing with the other hand. This experiment was based on the assumption that saw movement is controlled consistently at a predictable rate without the need for paying primary attention to it. It would follow that consciously matching different stipulated metronome rates with the other hand would result in the spontaneous performance of polyrhythms. Six experimental conditions were randomised: single handed tapping and sawing as well as four bimanual conditions with expected ratios of 1:1 (performed with and without matching a metronome) as well as 3:4 and 4:3 (performed matching a metronome). Results showed that participants executed the saw movement at a consistent cycle duration of 0.44 [0.20] s to 0.51 [0.19] s across single and bimanual conditions, with no significant effect of the condition on the cycle duration (p = 0.315). Similarly, free tapping was executed at a cycle duration of 0.48 [0.22] s. In the bimanual conditions, we found that for a ratio of 4:3 (4 taps against 3 sawing cycles per measure), the observed and predicted ratio of 0.75 were not significantly different (p = 0.369), supporting our hypothesis of the spontaneous adoption of polyrhythms. However, for a ratio of 3:4 (3 taps against 4 sawing cycles per measure), the observed and predicted ratio differed (p = 0.016), with a trend towards synchronisation. Our findings show that bimanual independence when performing complex polyrhythms can in principle be achieved if the movement of one hand can be performed without paying much-if any-attention to it. In this paradigm, small rhythmic arm movements are possibly driven by an intrinsic timing which leads to spontaneous convergence on a cycle duration of around 0.5 s, while the movement of the other hand can be controlled consciously to occur at desired rates.

Body-scaled perception is subjected to adaptation when repetitively judging opportunities for grasping

Experimental evidence is given that the perceptual system adapts to repetitive task execution in a perceptual two-choice judgment task. Participants were tested with respect to their perception of opportunities for plank grasping. Participants had to report whether planks were perceived as objects being graspable with either one hand or two hands. When the plank size was gradually increased and subsequently decreased, transitions from one hand judgments to two hands judgments and vice versa were observed. Analysis of the transition scores revealed that the perceptual judgments were body-scaled, as it is known in the literature. However, judgments were also found to be context dependent. Judgment transition scores were affected in a systematic way by the kind of and the number of previously made judgments. The latter quantitative impact was observed in three related experiments and suggests that perceptual judgments about opportunities for action adapt to task repetition. Overall, the experimental findings are consistent with the predictions of a dynamical systems model, which assumes that perceptual judgments are emergent properties of a self-organizing process that involves inhibitory top-down feedback.

Prospectively identified deficits in sagittal plane hip-ankle coordination in female athletes who sustain a second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport

BACKGROUND

Athletes who return to sport after anterior cruciate ligament reconstruction are at increased risk of future ACL injury. Altered coordination of lower extremity motion may increase this risk. The purpose of this study was to prospectively determine if altered lower extremity coordination patterns exist in athletes who go on to sustain a 2nd anterior cruciate ligament injury.

METHODS

Sixty-one female athletes who were cleared to return to sport after anterior cruciate ligament reconstruction were included. Hip-ankle coordination was assessed prior to return to sport with a dynamic postural coordination task. Within 12 months, 14 patients sustained a 2nd ACL injury. Fourteen matched subjects were selected for comparative analysis. Cross-recurrence quantification analysis characterized hip-ankle coordination patterns. A group × target speed (slow vs. fast) × leg (involved vs. uninvolved) analysis of variance was used to identify differences.

FINDINGS

A main effect of group (P = 0.02) indicated that the single injury group exhibited more stable hip-ankle coordination [166.2 (18.9)] compared to the 2nd injury group [108.4 (10.1)]. A leg × group interaction was also observed (P = .04). The affected leg of the single injury group exhibited more stable coordination [M = 187.1 (23.3)] compared to the affected leg of the 2nd injury group [M = 110.13 (9.8)], P = 0.03.

INTERPRETATION

Hip-ankle coordination was altered in female athletes who sustained a 2nd anterior cruciate ligament injury after return to sport. Failure to coordinate lower extremity movement in the absence of normal knee proprioception may place the knee at risk.

Performing Isometric Force Control in Combination with a Cognitive Task: A Multidimensional Assessment

Introduction

We used a multidimensional approach to study isometric force control in single and dual-task conditions.

Methods

Multiple measures of performance, efficiency, variability, and structural interference were calculated at low and higher force levels under single (force maintenance) and dual-task (force maintenance and reaction time) conditions.

Results

Reaction time and signal-to-noise ratio were larger in the dual-task conditions. They were also greater for the higher force condition, while sample entropy was lower. Perturbation analyses revealed smaller relative amplitude of downward perturbations for the higher force level.

Discussion

Attentional effort and efficiency are positively related when force level increases, and inversely related to entropy. These relations were presumably mediated by attentional investment. Behavioral perturbations show that attentional resources and structural interference models are not mutually exclusive to account for dual-task situation. Overall, the present study highlights the interest of a multidimensional assessment of force control.

Philosophy for the rest of cognitive science

Cognitive science has always included multiple methodologies and theoretical commitments. The philosophy of cognitive science should embrace, or at least acknowledge, this diversity. Bechtel's (2009a) proposed philosophy of cognitive science, however, applies only to representationalist and mechanist cognitive science, ignoring the substantial minority of dynamically oriented cognitive scientists. As an example of nonrepresentational, dynamical cognitive science, we describe strong anticipation as a model for circadian systems (Stepp & Turvey, 2009). We then propose a philosophy of science appropriate to nonrepresentational, dynamical cognitive science.

Differing Dynamics of Intrapersonal and Interpersonal Coordination: Two-finger and Four-Finger Tapping Experiments

Finger-tapping experiments were conducted to examine whether the dynamics of intrapersonal and interpersonal coordination systems can be described equally by the Haken—Kelso—Bunz model, which describes inter-limb coordination dynamics. This article reports the results of finger-tapping experiments conducted in both systems. Two within-subject factors were investigated: the phase mode and the number of fingers. In the intrapersonal experiment (Experiment 1), the participants were asked to tap, paced by a gradually hastening auditory metronome, looking at their fingers moving, using the index finger in the two finger condition, or the index and middle finger in the four-finger condition. In the interpersonal experiment (Experiment 2), pairs of participants performed the task while each participant used the outside hand, tapping with the index finger in the two finger condition, or the index and middle finger in the four-finger condition. Some results did not agree with the HKB model predictions. First, from Experiment 1, no significant difference was observed in the movement stability between the in-phase and anti-phase modes in the two finger condition. Second, from Experiment 2, no significant difference was found in the movement stability between the in-phase and anti-phase mode in the four-finger condition. From these findings, different coordination dynamics were inferred between intrapersonal and interpersonal coordination systems against prediction from the previous studies. Results were discussed according to differences between intrapersonal and interpersonal coordination systems in the availability of perceptual information and the complexity in the interaction between limbs derived from a nested structure.

Conversation and coordinative structures

People coordinate body postures and gaze patterns during conversation. We review literature showing that (1) action embodies cognition, (2) postural coordination emerges spontaneously when two people converse, (3) gaze patterns influence postural coordination, (4) gaze coordination is a function of common ground knowledge and visual information that conversants believe they share, and (5) gaze coordination is causally related to mutual understanding. We then consider how coordination, generally, can be understood as temporarily coupled neuromuscular components that function as a collective unit known as a coordinative structure in the motor control literature. We speculate that the coordination of gaze and body sway found in conversation may be understood as a cross-person coordinative structure that embodies the goals of the joint action system.

Symmetry and order parameter dynamics of the human odometer

Bipedal gaits have been classified on the basis of the group symmetry of the minimal network of identical differential equations (alias cells) required to model them. Primary bipedal gaits (e.g., walk, run) are characterized by dihedral symmetry, whereas secondary bipedal gaits (e.g., gallop-walk, gallop- run) are characterized by a lower, cyclic symmetry. This fact has been used in tests of human odometry (e.g., Turvey et al. in P Roy Soc Lond B Biol 276:4309-4314, 2009, J Exp Psychol Hum Percept Perform 38:1014-1025, 2012). Results suggest that when distance is measured and reported by gaits from the same symmetry class, primary and secondary gaits are comparable. Switching symmetry classes at report compresses (primary to secondary) or inflates (secondary to primary) measured distance, with the compression and inflation equal in magnitude. The present research (a) extends these findings from overground locomotion to treadmill locomotion and (b) assesses a dynamics of sequentially coupled measure and report phases, with relative velocity as an order parameter, or equilibrium state, and difference in symmetry class as an imperfection parameter, or detuning, of those dynamics. The results suggest that the symmetries and dynamics of distance measurement by the human odometer are the same whether the odometer is in motion relative to a stationary ground or stationary relative to a moving ground.

Grouping feedback components by common fate benefits motor-respiratory coordination

The purpose of this study was to see how motor-respiratory coordination could improve with augmented visual feedback. Participants performed inphase and antiphase patterns between movement and breathing. When the target pattern was performed properly, balls in a feedback display either moved up and down together (inphase feedback) or opposite each other (antiphase feedback). Relative phase performance was less variable in the augmented feedback conditions than in a no display control condition. Within the augmented feedback conditions, variability was lower with inphase feedback than antiphase feedback. Cross-recurrence analysis was used to determine whether other changes occurred on shorter time scales. On cross-recurrence measures, performance was more variable with inphase feedback than in the control condition and with antiphase feedback. Those results suggest that, with inphase feedback, participants were able to achieve more stable overall relative phase patterns using small within-cycle trajectory changes. Those small changes were possible because the balls in the inphase feedback display were grouped by common fate. That perceptual organization made it possible for participants to see slight mismatches between movement and breathing and control coordination accordingly.

Aging induced loss of complexity and dedifferentiation: consequences for coordination dynamics within and between brain, muscular and behavioral levels

Growing evidence demonstrates that aging not only leads to structural and functional alterations of individual components of the neuro-musculo-skeletal system (NMSS) but also results in a systemic re-organization of interactions within and between the different levels and functional domains. Understanding the principles that drive the dynamics of these re-organizations is an important challenge for aging research. The present Hypothesis and Theory paper is a contribution in this direction. We propose that age-related declines in brain and behavior that have been characterized in the literature as dedifferentiation and the loss of complexity (LOC) are: (i) synonymous; and (ii) integrated. We argue that a causal link between the aforementioned phenomena exists, evident in the dynamic changes occurring in the aging NMSS. Through models and methods provided by a dynamical systems approach to coordination processes in complex living systems, we: (i) formalize operational hypotheses about the general principles of changes in cross-level and cross-domain interactions during aging; and (ii) develop a theory of the aging NMSS based on the combination of the frameworks of coordination dynamics (CD), dedifferentiation, and LOC. Finally, we provide operational predictions in the study of aging at neural, muscular, and behavioral levels, which lead to testable hypotheses and an experimental agenda to explore the link between CD, LOC and dedifferentiation within and between these different levels.

Word generation affects continuous hand movements

Understanding interactions between cognitive and motor performance is an important theoretical and practical aim of motor neuroscience. Toward this aim, we invited university students to move one hand back and forth at a self-paced rate either in silence or while overtly generating words from semantic categories. The same participants also generated words without movement. Word generation affected manual performance but manual performance did not affect word generation. Only the timing, but not the spatial features, of the hand movements were influenced by word generation. The simplicity of our procedure argues for its future use, both for theoretical and practical purposes.

Dynamics of players' relative positioning during baseline rallies in tennis

This study analysed how the relative positioning of players on court influenced patterns of interpersonal coordination in baseline rallies in tennis. We developed a model (PA index) that assigns a weight to the position of each player on court and determines a positional advantage, based on the relative proportionality between the lateral and longitudinal displacement values during rallies. To test the model, data from 27 randomly-selected baseline rallies from three ATP World Tour matches (professional tennis players' tournaments organized by Association of Tennis Professionals) on clay were analysed. Results revealed that the PA index of players on court described their interpersonal coordination dynamics during baseline rallies. It also identified the emergence of rally breaks in the interpersonal coordination patterns of competing dyads that led to a point being scored. Data suggest that positional advantage data may assist coaches in the design of training tasks to enhance players' court coverage and performance during competitive interactions, acting as a valuable tool for performance analysis in tennis.

Inter-segmental postural coordination measures differentiate athletes with ACL reconstruction from uninjured athletes

Athletes who sustain non-contact anterior cruciate ligament (ACL) injuries and undergo surgical reconstruction exhibit deficits in sensorimotor control, which often impairs lower-limb movement coordination. The purpose of this experiment was to measure the influence of sensorimotor deficits on the ankle-hip coordination of a postural coordination task in athletes following ACL reconstruction. Twenty-two female athletes who were cleared to return to sports participation following ACL reconstruction and 22 uninjured female athletes performed a unilateral dynamic postural rhythmic coordination task at two movement frequencies (0.2 and 0.7 Hz). Athletes with ACL-reconstruction exhibited greater ankle-hip relative phase variability and reduced regularity of coupling than uninjured athletes, especially during the 0.2 Hz condition. The results of this study show altered lower extremity coordination patterns in athletes following ACL reconstruction and return to sports participation. The results also indicate that dynamical coordination measures may provide objective measures of sensorimotor deficits following ACL reconstruction and can potentially guide rehabilitation interventions following reconstruction.

Dynamics of cognition

The application of dynamical systems methods and concepts to cognitive phenomena has broadened the range of testable hypotheses and theoretical narratives available to cognitive scientists. Most research in cognitive dynamics tests the degree to which observed cognitive performance is consistent with one or another core phenomena associated with complex dynamical systems, such as tests for phase transitions, coupling among processes, or scaling laws. Early applications of dynamical systems theory to perceptual-motor performance and developmental psychology paved the way for more recent applications of dynamical systems analyses, models, and theoretical concepts in areas such as learning, memory, speech perception, decision making, problem solving, and reading, among others. Reviews of the empirical results of both foundational and contemporary cognitive dynamics are provided. WIREs Cogn Sci 2012. doi: 10.1002/wcs.1200 For further resources related to this article, please visit the WIREs website.

Nesting of asymmetric functions in skilled bimanual action: dynamics of hammering behavior of bead craftsmen

In human manual activities, the two hands are often engaged in differentiated roles while cooperating with each other to produce an integrated outcome. Using recurrence methods, we studied the asymmetric bimanual action involved in stone bead production by craftsmen of different skill levels, and examined (a) how the control of unilateral movement is embedded in that of a bimanual system, and (b) how the behavior of a bimanual system is embedded in the context of the function performed in the world. Evidence was found that the movements of the two hands of experts were functionally linked, reflecting the roles assumed by each hand. We further found that only the dynamics of bimanual coordination of experts differentiated the functional requirements of different sub-goals. These results suggest that expertise in this skilled bimanual action lies in the nesting of functionally specific adjustments at different levels of a control hierarchy.

The blue-collar brain

Much effort has gone into elucidating control of the body by the brain, less so the role of the body in controlling the brain. This essay develops the idea that the brain does a great deal of work in the service of behavior that is controlled by the body, a blue-collar role compared to the white-collar control exercised by the body. The argument that supports a blue-collar role for the brain is also consistent with recent discoveries clarifying the white-collar role of synergies across the body's tensegrity structure, and the evidence of critical phenomena in brain and behavior.

Gestures, but not meaningless movements, lighten working memory load when explaining math

Gesturing is ubiquitous in communication and serves an important function for listeners, who are able to glean meaningful information from the gestures they see. But gesturing also functions for speakers, whose own gestures reduce demands on their working memory. Here we ask whether gesture's beneficial effects on working memory stem from its properties as a rhythmic movement, or as a vehicle for representing meaning. We asked speakers to remember letters while explaining their solutions to math problems and producing varying types of movements. Speakers recalled significantly more letters when producing movements that coordinated with the meaning of the accompanying speech, i.e., when gesturing, than when producing meaningless movements or no movement. The beneficial effects that accrue to speakers when gesturing thus seem to stem not merely from the fact that their hands are moving, but from the fact that their hands are moving in coordination with the content of speech.

Effects of age, task, and frequency on variability of finger tapping

The goal was to assess whether prior studies might have overestimated performance variability in older adults in dual task conditions by relying on primary motor tasks that are not constant with aging. 30 younger and 31 older adults performed a bimanual tapping task at four different frequencies in isolation or concurrently with a secondary task. Results showed that performance of younger and older adults was not significantly different in performing the tapping task at all frequencies and with either secondary task, as indicated by mean tapping performance and low number of errors in the secondary tasks. Both groups showed increased variability as tapping frequency increased and with the presence of a secondary task. Tapping concurrently while reading words increased tapping variability more than tapping concurrently while naming colours. Although older participants' performances were overall more variable, no interaction effects with age were found and at the highest frequencies of tapping, younger and older participants did not differ in performance.

Dual-Hierarchical Control Mechanism of Interpersonal Embodied Interactions in Cooperative Walking

Interpersonal embodied interactions play a significant role as emergent functions in human development and rehabilitation. However, a framework for applying embodied interactions to “human interface systems” to support such emergent functions has not yet been suggested because the details of the motorcontrol mechanism have not yet been clarified. In this study, the interpersonal cooperative walking motions of two humans, as an example of such a mechanism, have been replicated and their motor-control mechanisms analyzed. The results indicate that the hierarchical dynamics were derived from an interpersonal footstep entrainment process and an intrapersonal interaction of arm and footstep motions. We suggest that embodied interactions in cooperative walking are achieved by a dual-hierarchical control structure related to emergence of the phase-control function of interpersonal cooperative walking, based on an automatic control mechanism for interpersonal entrainment of footstep motions and an intrapersonal voluntary-motion-control mechanism.

Multi-segmental postural coordination in professional ballet dancers

Ballet dancers have heightened balance skills, but previous studies that compared dancers to non-dancers have not quantified patterns of multi-joint postural coordination. This study utilized a visual tracking task that required professional ballet dancers and untrained control participants to sway with the fore-aft motion of a target while standing on one leg, at target frequencies of 0.2 and 0.6Hz. The mean and variability of relative phase between the ankle and hip, and measures from cross-recurrence quantification analysis (i.e., percent cross-recurrence, percent cross-determinism, and cross-maxline), indexed the coordination patterns and their stability. Dancers exhibited less variable ankle-hip coordination and a less deterministic ankle-hip coupling, compared to controls. The results indicate that ballet dancers have increased coordination stability, potentially achieved through enhanced neuromuscular control and/or perceptual sensitivity, and indicate proficiency at optimizing the constraints that enable dancers to perform complex balance tasks.

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.

Structural changes in postural sway lend insight into effects of balance training, vision, and support surface on postural control in a healthy population

Postural sway was assessed [via center of pressure (COP) 95% elliptical area (EA), path length (PL), normalized path length (PL(n)) and sample entropy (SEn)] in four conditions of bipedal upright stance [compliant (Foam) vs. non-compliant (Hard) with eyes-open (EO) vs. eyes-closed (EC)] prior to, and immediately following, a six-week balance training intervention in a group of healthy adults (N = 26). The intervention was comprised of nine exercises progressed in difficulty based on the subjective assessments of individual competency. Results showed that EA and PL were increased, while PL(n) and SEn were decreased, in EC and Foam stance conditions (collapsed across effects of balance training). Interpretations were that restricted vision and a compliant surface represented constraints to postural control that caused increases in the amount (PL) and area (EA) of sway, but decreases in its coordinative twisting/turning (PL(n)) and temporal complexity (SEn). It was argued that these changes might represent compensatory adaptations in effort to maintain postural control given the demands of the imposed constraints. Balance training caused no change to EA, but did result in decreased PL, PL(n), and SEn for stance conditions performed on the Foam (either EO or EC). These changes were interpreted to reflect improved postural control, potentially through the learned adoption of a more deterministic postural control strategy that is uniquely defined by the constraints imposed on upright stance by the compliant surface.

Covariation of attentional cost and stability provides further evidence for two routes to learning new coordination patterns

This study investigated how learning a new bimanual coordination pattern affects the attentional resources allotted by the CNS to maintain it throughout the acquisition process. The repertoire of the existing stable coordination patterns was individually evaluated before and after practice in order to detect expected changes with learning. Bistable participants, who initially exhibited stable and accurate coordination patterns at 0 degrees and 180 degrees of relative phase, practiced a 90 degrees pattern, whereas multistable participants, who already mastered the 90 degrees pattern, practiced 135 degrees pattern instead. In a typical dual-task paradigm, all participants had to simultaneously perform a reaction time task that assessed the associated attentional cost. Beyond an overall increase in accuracy, the results revealed a significant decrease in the attentional cost for bistable participants, accompanying the stabilization of the 90 degrees pattern with learning, but not for multistable participants, as the 135 degrees pattern barely stabilized. Pattern stability and attentional cost co-evolve during learning and the process follows two different routes depending on the interplay between the task and the learner's coordination abilities before practice.

Sentence comprehension affects the dynamics of bimanual coordination: Implications for embodied cognition

Recent work in embodied cognition has demonstrated that language comprehension involves the motor system (e.g., Glenberg & Kaschak, 2002). Such findings are often attributed to mechanisms involving simulations of linguistically described events (Barsalou, 1999; Fischer & Zwaan, 2008). We propose that research paradigms in which simulation is the central focus need to be augmented with paradigms that probe the organization of the motor system during language comprehension. The use of well-studied motor tasks may be appropriate to this endeavour. To this end, we present a study in which participants perform a bimanual rhythmic task (Kugler & Turvey, 1987) while judging the plausibility of sentences. We show that the dynamics of the bimanual task differ when participants judge sentences describing performable actions as opposed to sentences describing events that are not performable. We discuss the general implications of our results for accounts of embodied cognition.

Attentional demands on motor-respiratory coordination

Athletic performance requires the pacing of breathing with exercise, known as motor-respiratory coordination (MRC). In this study, we added cognitive and physical constraints while participants intentionally controlled their breathing locations during rhythmic arm movement. This is the first study to examine a cognitive constraint on MRC. Cognitive constraints included either instruction (Experiments 1 and 2) or signal detection (Experiment 1). Physical constraints were nonoptimal movement frequencies (Experiment 2). Instruction shifted breathing locations and both shifted and increased variability in the number of movements produced per breath (frequency ratio). Signal detection had no effect on MRC. Fast movement frequency resulted in higher more variable frequency ratios. Cognitive and physical constraints can generate unnatural and variable breathing during athletic performance.

Comparing the attractor strength of intra- and interpersonal interlimb coordination using cross-recurrence analysis

Previous research has demonstrated that intra- and interpersonal rhythmic interlimb coordination are both constrained by the self-organizing entrainment process of coupled oscillators. Despite intra- and interpersonal coordination exhibiting the same stable macroscopic movement patterns the variability of the coordination is typically found to be much greater for inter- compared to intrapersonal coordination. Researchers have assumed that this is due to the interpersonal visual-motor coupling producing a weaker attractor dynamic than the intrapersonal neuromuscular coupling. To determine whether this assumption is true, two experiments were conducted in which pairs of participants coordinated hand-held pendulums swung about the wrist, either intra- and interpersonally. Using the cross-recurrence statistics of percent recurrence and maxline to independently index the level of noise and the attractor strength of the coordination, respectively, the results confirmed that the attractor strength was significantly weaker for inter- compared to intrapersonal coordination and that a similar magnitude of noise underlies both.