Learning to Minimize Energy Costs and Maximize Mechanical Work in a Bimanual Coordination Task

The authors addressed the hypothesis that economy in motor coordination is a learning phenomenon realized by both reduced energy cost for a given workload and more external work at the same prepractice metabolic and attentional energy expenditure. "Self-optimization" of movement parameters has been proposed to reflect learned motor adaptations that minimize energy costs. Twelve men aged 22.3 ± 3.9 years practiced a 90° relative phase, upper limb, independent ergometer cycling task at 60 rpm, followed by a transfer test of unpracticed (45 and 75 rpm) and selfpaced cadences. Performance in all conditions was initially unstable, inaccurate, and relatively high in both metabolic and attentional energy costs. With practice, coordinative stability increased, more work was performed for the same metabolic and attentional costs, and the same work was done at a reduced energy cost. Selfpaced cycling was initially below the metabolically optimal, but following practice at 60 rpm was closer to optimal cadence. Given the many behavioral options of the motor system in meeting a variety of everyday movement task goals, optimal metabolic and attentional energy criteria may provide a solution to the problem of selecting the most adaptive coordination and control parameters.     

The Representation of Action: Insights From Bimanual Coordination

ABSTRACT— The motor-program concept, emphasizing how actions are represented in the brain, helped bring the study of motor control into the realm of cognitive psychology. However, interest in representational issues was in limbo for much of the past 30 years, during which time the focus was on biomechanical and abstract accounts of the constraints underlying coordinated movement. We review recent behavioral and neuroscientific evidence that highlights multiple levels of constraints in bimanual coordination, with an emphasis on work demonstrating that a primary source of constraint arises from the manner in which action goals are represented.     

Development of Bimanual Skill: The Search for Stable Patterns of Coordination

In 2 experiments, dynamic systems theory predictions concerning intrinsic dynamics and variability of bimanual coordination were examined at different developmental stages. In Experiment 1, ten 4-, 6-, 7-, 8-, and 10-year-old children and adults performed unimanual dominant, unimanual nondominant, and bimanual continuous circle drawing. All tasks were performed at the participants' preferred rate, size, and mode of coordination. The 4-, 6-, and 7-year-old children produced larger circles with longer durations than those of the 8- and 10-year-olds and the adults. That finding demonstrates that younger children display different intrinsic dynamics than older children and adults. The 4-, 6-, and 7-year-old children also displayed more variability in bimanual coordination (more time in less stable patterns of coordination, higher standard deviation in relative phase) and produced more transitions between coordination patterns than the 8- and 10-year-olds and the adults. In Experiment 2, the same participants performed bimanual circles at increasing rates. Consistent with predictions of the HKB model (H. Haken, J. A. S. Kelso, & H. Bunz, 1985), the number of transitions decreased as speed increased. Some support was found for the notion that age-related variables of attention and rate contribute to the increased variability in young children's bimanual coordination.     

Bimanual Finger Tapping: Effects of Frequency and Auditory Information on Timing Consistency and Coordination

The authors' goal in this study was to probe the basis for an earlier, unexpected finding that preferred-frequency finger tapping tends to have higher frequencies and to be less stable for in-phase than for antiphase tasks. In follow-up experiments, 3 protocols were employed: a preferred-frequency replication in both coordination modes, a metronome-driven matching of the preferred frequencies to each of the coordination modes, and a frequency scaling of both modes. The original findings were affirmed for preferred frequency. Tapping to a metronome had a differential effect on in-phase and antiphase: A more stable coupling across frequencies was exhibited during in-phase. Under frequency scaling, the antiphase pattern decomposed at lower frequencies than did in-phase, but no phase transitions were observed. The loss of stable coordination in both modes was attended by sudden increases in frequency differences between fingers and by phase wandering. The emergence of those effects is discussed in light of asymmetric modifications to the Haken-Kelso-Bunz model (H. Haken, J. A. S. Kelso, & H. Bunz, 1985) and the task constraints of tapping.     

Coordination Dynamics of the Horse-Rider System

The authors studied the interaction between rider and horse by measuring their ensemble motions in a trot sequence, comparing 1 expert and 1 novice rider. Whereas the novice's movements displayed transient departures from phase synchrony, the expert's motions were continuously phase-matched with those of the horse. The tight ensemble synchrony between the expert and the horse was accompanied by an increase in the temporal regularity of the oscillations of the trunk of the horse. Observed differences between expert and novice riders indicated that phase synchronization is by no means perfect but requires extended practice. Points of contact between horse and rider may haptically convey effective communication between them.     

Spatial Conceptual Influences on the Coordination of Bimanual Actions: When a Dual Task Becomes a Single Task

When the left and right hands produce 2 different rhythms simultaneously, coordination of the hands is difficult unless the rhythms can be integrated into a unified temporal pattern. In the present study, the authors investigated whether a similar account can be applied to the spatial domain. Participants (N = 8) produced a movement trajectory of semicircular form in single-limb and bimanual conditions. In the bimanual tasks, 1 limb moved above the other in the frontal plane. Bimanual unified tasks were constructed so that the spatial paths to be produced by the 2 limbs could be easily conceptualized as parts of a unified circle pattern. Bimanual distinct tasks availed a less obvious spatial pattern that would unify the 2 tasks. Performance of the spatial patterns was more accurate in the unified task, despite similar demands placed on the coordination dynamics between the limbs in the 2 cases (e.g., the phase relations). The authors conclude that a dual task becomes a single task, and interlimb interference is reduced, when the spatial patterns produced by the 2 hands form a geometric arrangement that can be conceptualized as a unified representation.     

Catching With Both Hands: An Evaluation of Neural Cross-Talk and Coordinative Structure Models of Bimanual Coordination

Kelso, Southard, and Goodman (1979) and Marteniuk and MacKenzie (1980) have each proposed a different theoretical model for bimanual coordination. In the model of Kelso et al., a close temporal relationship between the hands in a bimanual task is predicted, even when each hand is required to move different distances. In Marteniuk and MacKenzie's model, separate motor commands are issued so that each limb will arrive simultaneously at the specified movement endpoint, leading to low temporal associations between limbs. In most previous work on bimanual coordination, manual aiming tasks with differing constraints have been used by subjects in individual studies. In this study, the usefulness of existing models for predicting performance in a real-world catching task in which the required movement pattern was constrained by ball flight characteristics was examined. Eleven university students caught tennis balls with both hands in the following 3 conditions: Condition 1. Ball projected to the right shoulder area (left hand moved a greater distance than the right); Condition 2. Ball projected to center of the chest area, (both hands moved same distance); and Condition 3. Ball projected to left shoulder area (right hand moved a greater distance). Kinematic data (time to peak velocity, movement initiation time) indicating significant cross-correlations between the left and right limbs in all 3 conditions concurred with the data of Kelso et al. (1979) on manual aiming. Timing appeared to be an essential variable coordinating bimanual interceptive actions. Although the limbs moved at different speeds when each was required to move different distances, times to peak velocity showed strong associations, suggesting the presence of a coordinative structure.     

Effects of Visual Information and Task Constraints on Intersegmental Coordination in Playground Swinging

The authors investigated how and to what extent visual information and associated task constraints are negotiated in the coordinative structure of playground swinging. Participants (N = 20) were invited to pump a swing from rest to a prescribed maximal amplitude under 4 conditions: normal vision, no vision, and 2 visual conditions involving explicit phasing constraints. In the latter conditions, participants were presented with a flow pattern consisting of a periodically expanding and contracting optical structure. They were instructed to phase the swing motion so that the forward turning point coincided with either the maximal size (enhanced optical flow) or the minimal size (reduced optical flow) of the presented flow pattern. Removal of visual information clearly influenced the swinging behavior, in that intersegmental coordination became more stereotyped, reflecting a general stiffening of the swinger. The conditions involving explicit phasing requirements also affected the coordination, but in an opposite way: The coordination became less stereotyped. The two phasing instructions had differential effects: The intersegmental coordination deviated more from normal swinging (i.e., without phasing constraints) when optical flow was enhanced than when it was reduced. Collectively, those findings show that visual information plays a formative role in the coordinative structure of swinging, in that variations of visual information and task constraints were accompanied by subtle yet noticeable changes in intersegmental coordination.     

Age Changes in Interlimb Coupling and the Development of Bimanual Coordination

Changes in interlimb coupling, and their role in the development of bimanual coordination, were studied longitudinally in 6- to 12-month-old infants (N = 6). Infants were observed while they were reaching for simple objects of 2 different sizes. Their use of a uni-versus bimanual strategy for reaching as well as the coupling of their bimanual movements were compared; progress in bimanual coordination of complementary movements was evaluated on 8 different bimanual tasks. The bimanual tasks involved an asymmetrical cooperation between the 2 hands. Although spatiotemporal coupling of bimanual reaching movements did not decrease during the age period studied, infants around 7 months of age used their 2 hands infrequently for reaching. Occurrences of bimanual reaching were particularly low at the session preceding the first bimanual success at a bimanual task. This suggests that the temporal coincidence between greater independence of the 2 hands and progress in bimanual coordination of complementary movements acts in 2 directions: Infants may be more at ease when using their 2 hands in differentiated patterns as the hands move less in synchrony, but, in turn, they may be less likely to move their hands in synchrony as the anticipate mirror manipulations of the object less. The frequency of bimanual reaches increased toward the end of the 1st year. This might have been caused by an increase in the repertoire of bimanual asymmetrical object manipulations and by the fact that the development of bimanual coordination allows infants to manipulate objects with complementary movements even after a bimanual approach toward the object.     

Motion sickness preceded by unstable displacements of the center of pressure

We exposed standing participants to optic flow in a moving room. Motion sickness was induced by motion that simulated the amplitude and frequency of standing sway. We identified instabilities in displacements of the center of pressure among participants who became sick; these instabilities occurred before the onset of subjective motion sickness symptoms. Postural differences between Sick and Well participants were observed before exposure to the nauseogenic stimulus. During exposure to the nauseogenic stimulus, sway increased for participants who became sick but also for those who did not. However, at every point during exposure sway was greater for participants who became motion sick. The results reveal that motion sickness is preceded by instabilities in displacements of the center of pressure.     

Age-Related Differences in the Rhythmic Structure of the Golf Swing

Participants were 20 younger golfers (M age = 19.8 years, SD = 1.84 years) and 20 older golfers (M age = 63.0 years, SD = 2.55 years) who attempted 40- and 80-yard eight-iron shots requiring an adjustment of their force and timing. No age-related differences were found in the tempo or speed of the shot; however, there were differences in the rhythmic relationship between the clubhead force and the weight shift. Whereas younger golfers primarily exhibited a 3 versus 2 polyrhythmic pattern between the peak forces of the clubhead and weight shift, older golfers primarily exhibited a simpler 3 versus 3 rhythmic force pattern by adding a forward weight shift at the beginning of the shot. Additionally, older golfers exhibited less independence between the timing of the clubhead force and weight shift, which indicated greater use of a single integrated coordinative unit rather than 2 units. These findings are interpreted as compensations for age-related slowing and increased temporal variability that help to preserve tempo at a speed comparable to younger adults.     

Visual Information and the Control of Reaching in Children: A Comparison Between Children With and Without Developmental Coordination Disorder

Three experiments were performed on reach and grasp in 9- to 10-year-old children (8 controls and 8 with developmental coordination disorder [DCD]). In normal reaching, children in the DCD group were less responsive to the accuracy demands of the task in controlling the transport component of prehension and spent less time in the deceleration phase of hand transport. When vision was removed as movement began, children in the control group spent more time decelerating and reached peak aperture earlier. Children in the DCD group did not do that, although, like the control group, they did increase grip aperture in the dark. When depth cues were reduced and only the target or only the target and hand were visible, children in the control group used target information to maintain the same grip aperture in all conditions, but DCD children behaved as if the target was not visible. Throughout the studies, the control group of 9- to 10-year-olds did not produce adult-like adaptations to reduced vision, suggesting that they had not yet attained adult-like integration of sensory input. Compared with control children, children with DCD did not exhibit increased dependence on vision but showed less recognition of accuracy demands, less adaptation to the removal of vision, and less use of minimal visual information when it was available.     

Developmental Characteristics of Disparate Bimanual Movement Skills in Typically Developing Children

Mastery of many tasks in daily life requires role differentiated bimanual hand use with high spatiotemporal cooperation and minimal interference. The authors investigated developmental changes in the performance of a disparate bimanual movement task requiring sequenced movements. Age groups were attributed to changes in CNS structures critical for bimanual control such as the corpus callosum (CC) and the prefrontal cortex; young children (5–6 years old), older children (7–9 years old), and adolescents (10–16 years old). Results show qualitative changes in spatiotemporal sequencing between the young and older children which typically marks a phase of distinct reduction of growth and myelination of the CC. Results show qualitative changes in spatiotemporal sequencing between the young and older children, which coincides with distinct changes in the growth rate and myelination of the CC. The results further support the hypothesis that CC maturation plays an important role in the development of bimanual skills.     

Managing the Rhythmic Complexity of Hitting a Golf Ball

ABSTRACT

The authors investigated how the force pattern exerted on a golf club is coordinated with the golfer's weight shift, which supplies power to the swing. Moderately skilled golfers (n = 10, 5–10 stroke handicap) hit short golf shots requiring different amounts of force. Across these different shots, the timing of the force pattern applied to the clubhead was approximately invariant even though the force magnitude varied. In contrast, the weight shift timing and magnitude both varied with the required force of the shot. Across repeated attempts at the same shot, temporal variations in the clubhead force pattern were either uncorrelated or only weakly correlated with temporal variations in the weight shift. Together, these data indicate that the weight shift is a relatively independent, adjustable rhythmic unit from the invariant clubhead timing pattern for moderately skilled golfers.     

An exploratory assessment of theory of mind and psychological impairment in patients with bulimia nervosa

This study aimed to investigate psychosocial functioning and different dimensions of theory of mind (ToM) in people with bulimia nervosa (BN) and Eating Disorder Not Otherwise Specified‐BN type (EDNOS‐BN). Psychosocial functioning and ToM were assessed in a sample of young adult females, 16 BN and 16 EDNOS‐BN outpatients and 16 healthy controls (HCs). They were assessed using the Eating Disorder Inventory‐Symptom Checklist‐2 (EDI‐2 SC) for evaluating psychological traits associated with eating disorders; the Symptom Checklist‐90‐Revised (SCL‐90‐R) for evaluating psychopathological status; and the Theory of Mind Assessment Scale (Th.o.m.a.s.), a semi‐structured interview aimed at assessing a person's different dimensions of ToM. The BN and EDNOS‐BN groups exhibited worse performance than the control group on all dimensions of the SCL‐90‐R, and on all dimensions of the EDI‐2 SC. The only difference for perfectionism was that BN obtained higher scores than EDNOS‐BN group. Our results also revealed an impairment of third‐person and second‐order ToM in patients with bulimia (BN and EDNOS‐BN) with respect to control subjects. These preliminary data have important implications for future empirical work, in that they provide valuable information regarding the importance of investigating the various facets of ToM ability separately, in order to provide a more detailed profile of ToM functioning in the clinical samples.     

Interplay of Biomechanical Constraints and Kinematic Strategies in Selecting Arm Postures

In this study, the authors examined the interplay between biomechanics and control strategies in the resolution of excess degrees of freedom at the joint level. Seven participants made aimed arm movements from 30 starting points and several starting postures to targets. Final arm postures for movements to a target exhibited substantial joint angle variation. Through regression modeling and by comparing observed final arm postures with biomechanically plausible postures, the authors identified 3 kinematic strategies: (a) Maintain deviations from the average angle at the starting point to the joint's final posture; (b) make torso rotations that are a fixed proportion of shoulder rotations; and (c) adopt a characteristic combination of 4 wrist-positioning approaches. The results demonstrated that kinematic strategies can account for substantial variance in final arm postures, if one takes into account 2 types of individual differences—those that arise inevitably from biomechanical constraints and those that reflect choices in movement strategy.     

Beyond Dyadic Coordination: Multimodal Behavioral Irregularity in Triads Predicts Facets of Collaborative Problem Solving

We hypothesize that effective collaboration is facilitated when individuals and environmental components form a synergy where they work together and regulate one another to produce stable patterns of behavior, or regularity, as well as adaptively reorganize to form new behaviors, or irregularity. We tested this hypothesis in a study with 32 triads who collaboratively solved a challenging visual computer programming task for 20 min following an introductory warm‐up phase. Multidimensional recurrence quantification analysis was used to examine fine‐grained (i.e., every 10 s) collective patterns of regularity across team members' speech rate, body movement, and team interaction with the shared user interface. We found that teams exhibited significant patterns of regularity as compared to shuffled baselines, but there were no systematic trends in regularity across time. We also found that periods of regularity were associated with a reduction in overall behavior. Notably, the production of irregular behavior predicted expert‐coded metrics of collaborative activity, such as teams' ability to construct shared knowledge and effectively negotiate and coordinate execution of solutions, net of overall behavioral production and behavioral self‐similarity. Our findings support the theory that groups can interact to form interpersonal synergies and indicate that information about system‐level dynamics is a viable way to understand and predict effective collaborative processes.     

Motion and edge sensitivity in perception of object unity

Although much evidence indicates that young infants perceive unitary objects by analyzing patterns of motion, infants' abilities to perceive object unity by analyzing Gestalt properties and by integrating distinct views of an object over time are in dispute. To address these controversies, four experiments investigated adults' and infants' perception of the unity of a center-occluded, moving rod with misaligned visible edges. Both alignment information and depth information affected adults' and infants' perception of object unity in similar ways, and infants perceived object unity by integrating information about object features over time. However, infants perceived a moving, misaligned, three-dimensional object as indeterminate in its connectedness, whereas adults perceived it as connected behind the occluder. These findings indicate that the effectiveness of common motion in specifying unified surfaces across an occluder is reduced by misalignment of edges. Alignment information enhances perception of object unity either by serving directly as information for unity or by optimizing the detectability of motion-carried information for unity. In addition, young infants are able to retain information about edge orientation over short intervals in determining connectedness via a process of spatiotemporal integration.     

Lost in the Rhythm: Effects of Rhythm on Subsequent Interpersonal Coordination

Music is a natural human expression present in all cultures, but the functions it serves are still debated. Previous research indicates that rhythm, an essential feature of music, can enhance coordination of movement and increase social bonding. However, the prolonged effects of rhythm have not yet been investigated. In this study, pairs of participants were exposed to one of three kinds of auditory stimuli (rhythmic, arrhythmic, or white‐noise) and subsequently engaged in five trials of a joint‐action task demanding interpersonal coordination. We show that when compared with the other two stimuli, exposure to the rhythmic beat reduced the practice effect in task performance. Analysis of the behavioral data suggests that this reduction results from more temporally coupled motor movements over successive trials and that shared exposure to rhythm facilitates interpersonal motor coupling, which in this context serves to impede the attainment of necessary dynamic coordination. We propose that rhythm has the potential to enhance interpersonal motor coupling, which might serve as a mechanism behind its facilitation of positive social attitudes.     

Compensatory Coordination of Release Parameters in a Throwing Task

The consistency and coordination of release parameters in ball-throwing movements were investigated. The authors used a newly developed index of coordination for release parameters (ICRP) that quantifies the degree of improvement of performance consistency caused by compensatory relationships among parameters (i.e., not caused by consistency of parameters). Eight participants practiced for 150 trials, with the nondominant hand, a ball-throwing task aimed at a stationary target. The magnitude of the ball-release velocity vector, among release parameters, as well as the performance was found to become consistent with practice. The ICRP score suggested that the release parameters were complementarily coordinated with one another, and that the coordination improved with practice. Those results indicate that compensatory relationships among varying release parameters contribute to reducing the variability of performance in a ball-throwing task whose goal is accuracy.