Spontaneous transitions and symmetry: Pattern dynamics in human four-limb coordination

Transitions between the coordinative patterns of rhythmically moving human arms and legs were studied to test the predictions of a four-component model (Schöner, Jiang and Kelso, 1990). Based upon results from previous two-component experiments (Kelso and Jeka, 1992), three assumptions were made about the four-limb system: (1) all limb pairs produce stable in-phase and anti-phase patterns; (2) the coupling between homologous limbs (i.e., right and left arms or right and left legs) is appreciably stronger than the coupling between nonhomologous limbs (i.e., arm and leg); and (3) right-left symmetry. An analysis of a four-component model (Jeka, Kelso and Kiemel, 1993) led to the prediction of four attracting invariant circles, each with two stable patterns in the state space of four-limb dynamics. In an experiment to test this prediction, subjects were required to cycle all four limbs in one of the eight patterns to the beat of an auditory metronome whose frequency was systematically increased. All subjects demonstrated spontaneous transitions corresponding to pathways along the invariant circles. Pre-transition relative phase variability increased with required frequency up to the transition, suggesting that loss of pattern stability induced the observed transitions. Thus, despite a large number of potential transitions, differential coupling between limb pairs and symmetry of the pattern dynamics restricts the behavior of the human four-limb system to a limited area of its state space.     

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.     

Overcoming spontaneous patterns of coordination during the acquisition of a complex balancing task.

Learning in complex tasks is usually conceived as the problem of mastering the multiple and redundant degrees of freedom of the system. To reduce control requirements, two different strategies are conceivable. The first one consists of a "freezing-freeing" process for most articular joints to reduce the number of active biomechanical degrees of freedom to be managed. The second strategy consists of introducing rigid couplings between the oscillators building the system. In this case, learning implies the dissolution of initial couplings and the emergence of new, more task-specific couplings. The goal of our study was to analyze the spontaneous coordination of beginners and its development in a complex balancing task on a stabilometer, and to examine the emergence of these two strategies. Our results showed that beginners were characterized by strong couplings between the joints of the lower limbs. During learning, new and more task-specific couplings emerged that reflected a new organization of the trunk and a decoupling of some joints of the lower limbs that were initially coupled during the first few trials.     

Self-organized criticality and learning a new coordination task

The purpose of this study was to investigate the hypothesis that a self-organized criticality (SOC) practice condition would have a higher improvement rate in performance outcome than a typical progressive difficulty of practice regimen. The roller ball task was used where participants undergo a phase transition from failure to successful performance after sufficient practice. The findings from two experiments showed that the SOC condition had the fastest rate of improvement and the highest performance success level. The success probability in the SOC practice regime was close to the theoretically predicted value of 50%. It appears that the SOC practice condition - by scaling task difficulty to skill level in a self-controlled adaptive strategy - facilitates the learning of new movement coordination pattern by keeping the participant close to the parameter region of the transition of the movement dynamics.     

Motion coordination affects movement parameters in a joint pick-and-place task

This study examined influences of social context on movement parameters in a pick-and-place task. Participants' motion trajectories were recorded while they performed sequences of natural movements either working side-by-side with a partner or alone. It was expected that movement parameters would be specifically adapted to the joint condition to overcome the difficulties arising from the requirement to coordinate with another person. To disentangle effects based on participants' effort to coordinate their movements from effects merely due to the other's presence, a condition was included where only one person performed the task while being observed by the partner. Results indicate that participants adapted their movements temporally and spatially to the joint action situation: Overall movement duration was shorter, and mean and maximum velocity was higher when actually working together than when working alone. Pick-to-place trajectories were also shifted away from the partner in spatial coordinates. The partner's presence as such did not have an impact on movement parameters. These findings are interpreted as evidence for the use of implicit strategies to facilitate movement coordination in joint action tasks.     

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, despite similar demands placed on the coordination dynamics 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.     

The control of amplitude and direction in a bimanual coordination task

Bimanual coordination requires task-specific control of the spatial and temporal characteristics of the movements of both hands. The present study focused on the spatial relationship between hand movements when their amplitude and direction were manipulated. In the experiment in question, participants were instructed to draw two lines simultaneously. These two lines were instructed to be drawn in mirror symmetric or perpendicular directions of each other while the length was instructed to be the same or different. The coordinative quality of amplitude control was compared when the task required symmetric and asymmetric bimanual spatial coordination patterns. Results showed that the amplitude accuracy decreased when different amplitudes and/or directions had to be generated simultaneously. The coordinative quality of direction was also compared when the task required symmetric and asymmetric bimanual spatial coordination patterns. Unlike amplitude, the direction accuracy was largely independent of coordination symmetry/asymmetry of direction or amplitude. The results suggest that the coordinative quality of amplitude control does not only interfere with amplitude asymmetry, but it also interferes with direction asymmetry. Moreover, in bimanual coordination amplitude control is more vulnerable to the influence of direction control demands than vice versa.     

Modeling developmental transitions on the balance scale task

Periods of relatively stable, rule‐like behavior alternated with short transition periods characterize cognitive development on reasoning tasks like the balance scale task. Each transition gives rise to an improvement in behavior, until a phase is reached in which performance is flawless or improvement is not worthwhile given the necessary extra effort. Several computational models have been developed to capture the developmental phenomena associated with the balance scale task. These models, which originate from different computational traditions, explain the main phenomena of development. Recently, empirical phenomena have been reported that these models cannot easily accommodate. We propose a computational model that is implemented in ACT‐R and that is based on the evaluation of success of applied knowledge, combined with a mechanism to construct newknowledge by searching for differences between the left‐ and right‐hand sides of presented balance scale problems. This model accounts for the main empirical phenomena as well as for the recently reported empirical phenomena such as learning without feedback.     

Skill level constrains the coordination of posture and upper-limb movement in a pistol-aiming task

The purpose of the experiment was to investigate whether skill level differentially organizes the coordination of the postural system and upper limb kinematics in a pistol-aiming task. Participants aimed an air-pistol at a target center in 30 s trials as accurately as possible while standing on a force platform with shooting arm joint kinematics recorded. The novice group had greater motion of the pistol end point, arm joints and the center of pressure than the skilled group. Principal components analysis (PCA) showed that the skilled group required 2 components as opposed to the 3 components of the novice group to accommodate the variance. Coherence analysis in the 0–1 Hz bandwidth revealed that the coupling between posture and upper-limb movement was stronger in the skilled than the novice group. The findings are consistent with the view that skill acquisition reduces the kinematic variables into a lower dimensional functional unit that in pistol-aiming is defined over the collective posture and upper-limb system.     

Developmental differences in the use of visual information during a continuous bimanual coordination task

The authors examined the influence of different amounts of visual information when children 4 (CH4), 6 (CH6), and 8 (CH8) years of age, and adults (n = 12 in each group) performed a steady-state bimanual circle-drawing coordination task at self-selected speeds. All participants maintained in-phase coordination, but different strategies for maintaining the pattern emerged. A predictable relationship between variability and age was not observed, in that the CH8 group was not necessarily more consistent than the CH6 and CH4 groups. The authors conclude that children are transitioning from dependence on kinesthetic feedback to reliance on visual feedback around age 8, as suggested by L. Hay, C. Bard, M. Fleury, and N. Teasdale (1991; L. Hay, M. Fleury, C. Bard, & N. Teasdale, 1994; L. Hay & C. Redon, 1997), and that future studies are needed to further explore visual and kinesthetic feedback as potential control parameters during coordination tasks in developing children.     

Visuomotor coordination and intermanual transfer for a proprioceptive reaching task

Two experiments were conducted to determine the role of head constraint, whether present or absent and arm exposure type (terminal or continuous) on the production of intermanual transfer to two types of visual distortion. Experiment 1 investigated intermanual transfer to binocular, lateral prism displacement where the prism base orientation for both eyes was in the same direction. Experiment 2 determined whether intermanual transfer could be produced to squint prism viewing where the prism base orientation for each eye was in an opposite direction (base-out prisms). In both experiments transfer was produced when either head movement during prism exposure was unconstrained or when a terminal arm exposure was employed. Maximal transfer was produced when both of these conditions were employed.     

Times for transitions between hand and foot responses in a self-paced task

In a self-paced task subjects responded to each of four equally probable signals with a different one of their four limbs. Response times were examined as a function of the 16 possible transitions between limbs. Repeated responses were shown to be faster than any other transitions, while responses following responses with an ipsilateral limb were relatively slow. The implications of these results for models for the “repetition effect” are discussed.     

Spontaneous private speech and performance on a delayed match-to-sample task

Spontaneous private speech samples were obtained from 65 kindergarten children (mean age 70.3 months) from one suburban (n = 36) and one city (n = 29) school as they worked alone on a delayed match-to-sample (DMS) task with three levels of difficulty (2, 10, and 30 sec delays). As expected increases in DMS delay intervals produced decreased performance and increases in private speech. The expected increased positive relationship between task relevant private speech and performance for longer delays was found in city children but not suburban children. Since mean IQ scores were significantly different for the two groups this variable was further examined in post hoc analyses and discussed along with socio-economic status as possible explanations for the observed school-sample differences. A within-subject comparison for all children showed the percentage of speaking trials correct at 30-sec delay to be significantly greater than the percentage of nonspeaking trials correct. The effect of one experimenter modeled trial on a subsequent 10 trials at 30-sec delay was to increase speech and performance and to show a stronger relationship between speech and performance than for premodeling trials. These exploratory findings with a relatively simple two color matching task suggest further explorations of spontaneous private speech as a way of studying internalization of self regulatory cognitive strategies.     

Age-related differences in the integration of sensory information during the execution of a bimanual coordination task

Young (n = 7) and elderly (n = 7) subjects performed bimanual coordination patterns in the transverse plane according to the in-phase or antiphase mode. Sensory information was manipulated through visual (with or without vision of the limbs) and proprioceptive input (with or without vibratory stimuli on one limb). Movement patterns with vibrations showed higher deviations from the intended relative phase than did those without vibrations. This finding suggests that the proprioceptive information induced by the vibrations and the movement interfered, leading to a disruption of the coordination patterns. In addition, as compared with the elderly, the young subjects performed more stable movements under normal circumstances but were more strongly affected by vibratory stimuli during the performance of in-phase movements. During antiphase movements, both age groups experienced a decrease of pattern stability. Furthermore, the absence or presence of visual feedback influenced the performance of the young subjects more than that of the elderly. The presence of vision led to stable in-phase movements, whereas a decrease of pattern stability was observed for antiphase movements. In general, these results demonstrate that manipulation of feedback sources affects young subjects more than elderly ones, and this can be related to a reduced sensory sensitivity as a function of aging.     

Mass perturbation of a body segment: 2. Effects on interlimb coordination

The shifts in relative phase that are observed when rhythmically coordinated limbs are submitted to asymmetric mass perturbations have typically been attributed to the induced eigenfrequency difference (delta omega) between limbs. Modeling the moving limbs as forced linear oscillators, however, reveals that asymmetric mass perturbations may induce a difference not only in eigenfrequency (i.e., delta omega not equal 0) but also in the covarying low-frequency control gains (i.e., delta k not equal 0). Because the inverse of the low-frequency control gain (k) reflects the level of muscular torque (input) required for a particular displacement from equilibrium (output), asymmetric mass perturbations may result in an imbalance in the muscular torques required for task performance (related to delta k not equal 0). Thus, it is possible that the effects attributed to delta omega were in fact mediated by delta k. In 2 experiments, the authors manipulated delta k and delta omega separately by applying mass perturbations to the lower legs of 9 participants. The relative phasing between the legs was not affected by delta k, but manipulation of delta omega (while delta k remained approximately 0) induced systematic relative phase shifts that were more pronounced for antiphase than for in-phase coordination. That indication that the coordination dynamics is indeed influenced by an imbalance in eigenfrequency is discussed vis-a-vis the question of how such a merely peripheral property may affect the underlying coordination process.     

The influence of ball-swing on the timing and coordination of a natural interceptive task

Successful interception relies on the use of perceptual information to accurately guide an efficient movement strategy that allows performers to be placed at the right place at the right time. Although previous studies have highlighted the differences in the timing and coordination of movement that underpin interceptive expertise, very little is known about how these movement patterns are adapted when intercepting targets that follow a curvilinear flight-path. The aim of this study was to examine how curvilinear ball-trajectories influence movement patterns when intercepting a fast-moving target. Movement timing and coordination was examined when four groups of cricket batters, who differed in their skill level and/or age, hit targets that followed straight or curvilinear flight-paths. The results revealed that when compared to hitting straight trials, (i) mixing straight with curvilinear trials altered movement coordination and when the ball was hit, (ii) curvilinear trajectories reduced interceptive performance and significantly delayed the timing of all kinematic moments, but there were (iii) larger decrease in performance when the ball swung away from (rather than in towards) the performer. Movement coordination differed between skill but not age groups, suggesting that skill-appropriate movement patterns that are apparent in adults may have fully emerged by late adolescence.     

Task coordination and aging: explorations of executive control processes in the task switching paradigm.

A number of models of cognitive aging suggest that older adults exhibit disproportionate performance decrements on tasks which require executive control processes. In a series of three studies we examined age-related differences in executive control processes and more specifically in the executive control processes which underlie performance in the task switching paradigm. Young and old adults were presented with rows of digits and were required to indicate whether the number of digits (element number task) or the value of the digits (digit value task) were greater than or less than five. Switch costs were assessed by subtracting the reaction times obtained on non-switch trials from trials following a task switch. Several theoretically interesting results were obtained. First, large age-related differences in switch costs were found early in practice. Second, and most surprising, after relatively modest amounts of practice old and young adults switch costs were equivalent. Older adults showed large practice effects on switch trials. Third, age-equivalent switch costs were maintained across a two month retention period. Finally, the main constraint on whether age equivalence was observed in task switching performance was memory load. Older adults were unable to capitalize on practice under high memory loads. These data are discussed in terms of their implications for both general and process specific cognitive aging models.     

Behavioural coordination of dogs in a cooperative problem-solving task with a conspecific and a human partner

The process of domestication has arguably provided dogs (Canis familiaris) with decreased emotional reactivity (reduced fear and aggression) and increased socio-cognitive skills adaptive for living with humans. It has been suggested that dogs are uniquely equipped with abilities that have been identified as crucial in cooperative problem-solving, namely social tolerance and the ability to attend to other individuals’ behaviour. Accordingly, dogs might be hypothesised to perform well in tasks in which they have to work together with a human partner. Recently, researchers have found that dogs successfully solved a simple cooperative task with another dog. Due to the simplicity of the task, this study was, however, unable to provide clear evidence as to whether the dogs’ successful performance was based on the cognitive ability of behavioural coordination, namely the capacity to link task requirements to the necessity of adjusting one’s actions to the partner’s behaviour. Here, we tested dogs with the most commonly used cooperative task, appropriate to test behavioural coordination. In addition, we paired dogs with both a conspecific and a human partner. Although dogs had difficulties in inhibiting the necessary action when required to wait for their partner, they successfully attended to the two cues that predicted a successful outcome, namely their partner’s behaviour and the incremental movement of rewards towards themselves. This behavioural coordination was shown with both a conspecific and a human partner, in line with the recent findings suggesting that dogs exhibit highly developed socio-cognitive skills in interactions with both humans and other dogs.     

Hand preference consistency and eye-hand coordination in young children during a motor task

Indications of earlier research are that individuals exhibiting a consistent hand preference are better coordinated on selected motor tasks than peers with inconsistent hand preference. The present study examined eye-hand coordination via inter- and intramodal matching behavior by handedness groups for 55 5- and 6-yr.-olds using the Pinboard Test. Analysis indicated the Consistent group scored better, leading to the speculation that children with consistent laterality may possess an advantage in interhemispheric communication, especially when the task requires coordination of both limbs.     

The influence of asymmetric force requirements on a multi-frequency bimanual coordination task

An experiment was designed to determine the impact of the force requirements on the production of bimanual 1:2 coordination patterns requiring the same (symmetric) or different (asymmetric) forces when Lissajous displays and goal templates are provided. The Lissajous displays have been shown to minimize the influence of attentional and perceptual constraints allowing constraints related to neural crosstalk to be more clearly observed. Participants (N = 20) were randomly assigned to a force condition in which the left or right limb was required to produce more force than the contralateral limb. In each condition participants were required to rhythmically coordinate the pattern of isometric forces in a 1:2 coordination pattern. Participant performed 13 practice trials and 1 test trial per force level. The results indicated that participants were able to effectively coordinate the 1:2 multi-frequency goal patterns under both symmetric and asymmetric force requirements. However, consistent distortions in the force and force velocity time series were observed for one limb that appeared to be associated with the production of force in the contralateral limb. Distortions in the force produced by the left limb occurred regardless of the force requirements of the task (symmetric, asymmetric) or whether the left or right limb had to produce more force than the contralateral limb. However, distinct distortions in the right limb occurred only when the left limb was required to produce 5 times more force than the right limb. These results are consistent with the notion that neural crosstalk can influence both limbs, but may manifest differently for each limb depending on the force requirements of the task.