Whole-body angular momentum in a complex dance sequence: Differences across skill levels

Due to the redundant degrees of freedom (DOF) and nonlinearity of reactional kinetic elements within the human motor apparatus, controlling the complex dynamics of the human musculoskeletal system presents considerable difficulties. Based on this challenge, Bernstein (1967) viewed skill development as the process whereby the central nervous system (CNS) gains mastery of kinematic DOF and kinetic reactional elements (passive forces, moments etc.), with the highest level of skill characterised by optimal exploitation of reactional elements in the achievement of movement goals. A previous kinematic investigation into coordination differences in a complex multidirectional dance sequence demonstrated that general unfreezing of kinematic DOF occurred as dance skill progressed (Chang et al., submitted for publication). To gain insight into the role of angular reactional elements in skill, the present kinetic study investigated angular momentum and associated variables across three skill levels (beginners, intermediates, experts) within this same complex dance sequence. The results showed that the angular momenta of segments and accompanying angular reactional elements generally increased with skill level. More specifically, the findings suggested that while improvements in movement economy from cancellation of angular momentum between body segments occur early in skill progression, later in skill progression, experts utilise increased whole-body angular momentum. Although this is energetically expensive, it may enhance the aesthetic value of dance movements, and/or have mechanical advantages. Overall, the findings here provide support for Bernstein’s (1967) model of skill development. Future research should quantify the relations between energy expenditure, key biomechanical variables that reflect skill and dance aesthetics as perceived by audiences.     

Differences in spatial-temporal parameters and arm-leg coordination in butterfly stroke as a function of race pace, skill and gender

Spatial-temporal parameters (velocity, stroke rate, stroke length) and arm-leg coordination in the butterfly stroke were studied as a function of race pace, skill (due to technical level, age, and experience) and gender. Forty swimmers (ten elite men, ten elite women, ten less-skilled men, and ten less-skilled women) performed the butterfly stroke at four velocities corresponding to the appropriate paces for the 400-m, 200-m, 100-m, and 50-m, respectively. Arm and leg stroke phases were identified by video analysis and used to calculate four time gaps (T1: the time difference between the start of the arms' catch phase and the start of the legs' downward phase of the first leg kick; T2: the time difference between the start of the arms' pull phase and the start of the legs' upward phase of the first leg kick; T3: the time difference between the start of the arms' push phase and the start of the legs' downward phase of the second leg kick; and T4: the time difference between the start of the arms' recovery and the start of the legs' upward phase of the second leg kick) and the total time gap (TTG), i.e., the sum of the four discrete time gaps. These values described the changing coupling of arm to leg actions over an entire stroke cycle. A significant race pace effect indicated that the synchronization between the key motor points of the arms and legs, which determine the starts and ends of the arm and leg stroke phases, increased with pace for all participants. A significant skill effect indicated that the elite swimmers had greater velocity, stroke length, and stroke rate and stronger synchronization of the arm and leg stroke phases than the less-skilled swimmers, due to smaller T2 and T3 and greater T1. A significant gender effect revealed greater velocity and stroke length for the men, and smaller T1 for the less-skilled women. These time gap differences between skill levels were related to the capacity of elite swimmers to assume a more streamlined position of trunk, head and upper limbs during leg actions, adopt a shorter glide and higher stroke rate to overcome great forward resistance, and generate higher forces and use better technique during the arm pull. Thus, coaches are advised to begin monitoring arm-leg coordination earlier in swimmers' careers to ensure that they attain their highest possible skill levels.     

Knowledge structures and the acquisition of a complex skill

The purpose of this study was to examine the viability of knowledge structures as an operationalization of learning in the context of a task that required a high degree of skill. Over the course of 3 days, 86 men participated in 9 training sessions and learned a complex video game. At the end of acquisition, participants' knowledge structures were assessed. After a 4-day nonpractice interval, trainees completed tests of skill retention and skill transfer. Findings indicated that the similarity of trainees' knowledge structures to an expert structure was correlated with skill acquisition and was predictive of skill retention and skill transfer. However, the magnitude of these effects was dependent on the method used to derive the expert referent structure. Moreover, knowledge structures mediated the relationship between general cognitive ability and skill-based performance.     

Differences in semantic encoding as a function of reading comprehension skill

Using a modified Stroop procedure, we examined the extent to which the semantic encoding of a word is governed by the context within which that word appears. Good and poor comprehenders named the color of target words following their reading of either sentences or single words representing the object nouns of the sentences. Target words represented contextually emphasized (appropriate) attributes of the object nouns, nonemphasized (inappropriate) attributes of these nouns, or object attributes not related to these nouns (neutral). For single-word contexts, all subjects exhibited equal semantic interference to appropriate and inappropriate targets, relative to neutral targets. For sentence contexts, however, good comprehenders exhibited semantic interference only to appropriate targets, whereas poor comprehenders again exhibited equal interference to appropriate and inappropriate targets. These findings suggest that differences in comprehension skill may be attributable, at least in part, to fundamental differences in the way in which sentences are semantically encoded.     

Variation in coordination of a discrete multiarticular action as a function of skill level

The authors investigated coordination modes that emerged as a function of the interaction between skill level and task constraints in a multiarticular kicking action. Five skilled, 5 intermediate, and 5 novice participants attempted to satisfy specific height and accuracy constraints in kicking a ball over a barrier. Skilled and intermediate groups demonstrated a functional coordination mode involving less joint involvement at the proximal joints and greater joint involvement at distal joints, mimicking a chip-like action in soccer. Conversely, the novice group tended to produce larger ranges of motion throughout the kicking limb in a driving-like kicking action. Key differences were also found for task outcome scores, joint angle-angle relations, and ball-trajectory plots between the skilled and intermediate groups and the novice group. Findings from this study demonstrated that joint involvement during this discrete multiarticular action is a function of skill level and task constraints rather than a consequence of a global freezing-freeing strategy suggested in some previous research. The authors also highlight the merit of using a model of the acquisition of coordination in examining how coordination modes for multiarticular actions differ as a function of skill.     

Learning a complex motor skill from video and point-light demonstrations

The aim of this study was to compare the learning process of a highly complex ballet skill following demonstrations of point-light and video models. 16 participants divided into point-light and video groups (ns = 8) performed 160 trials of a pirouette, equally distributed in blocks of 20 trials, alternating periods of demonstration and practice, with a retention test a day later. Measures of head and trunk oscillation, coordination disparity from the model, and movement time difference showed similarities between video and point-light groups; ballet experts' evaluations indicated superiority of performance in the video over the point-light group. Results are discussed in terms of the task requirements of dissociation between head and trunk rotations, focusing on the hypothesis of sufficiency and higher relevance of information contained in biological motion models applied to learning of complex motor skills.     

Learning of a complex arithmetic skill in amnesia: evidence for a dissociation between compilation and production

Two patients with severe amnesia following rupture of anterior communicating artery aneurysms were able to learn a complex algorithm for mentally squaring two-digit numbers. Although both patients learned the algorithm at a similar rate, one patient's improvement was accounted for by savings in the steps of the algorithm. The other patient, however, showed little improvement in the steps while performance of the whole algorithm improved dramatically. Neither patient showed savings in the Hebb Digit Span procedure. The results suggested a dissociation between amnesics in their capacity to learn the constituent "productions" or steps of a skill and their capacity to organize those productions into a single coherent act.     

Attention control and ability level in a complex cognitive skill: Attention shifting and second-language proficiency

In this study, we investigated the relationship between attention control and proficiency in a complex cognitive skill. The participants were English-French bilinguals with varying degrees of second-language (French) proficiency. Proficiency was operationalized as efficiency of lexical access in an animacy judgment task, as reflected in the coefficient of variability of response time adjusted for first-language performance on the same task. Attention control was operationalized as the shift cost obtained in a linguistic version of the alternating runs task-switching paradigm. Hierarchical regression revealed that, overall, attention control accounted for 59% of the variance of proficiency and that second-language attention control alone accounted for 32% of the unique variance of proficiency, indicating a high degree of skill domain (second language) specificity in the relationship between attention control and proficiency. The results speak to issues regarding the development of expertise, second-language acquisition, and a cognitive linguistic approach to language and attention.     

Attention in performance of a complex skill by retarded children.

Try materials were used to train 9 retarded children to attend to differences in colors and shapes of objects, and Frostig worksheets were used to train the children to attend to left-to-right directionality. Evidence suggests Ss' ability to attend to these characteristics was generalized to a complex bead-stringing task on which significant gains in performance were found immediately after 15 days of practice with training materials and after a 6-mo. interval of no further training or practice.     

Soccer player's and closed-skill athletes' execution of a complex motor skill

The main purpose of this study was to investigate possible differences in speed and accuracy of motor execution among female soccer players in an Expert Soccer group, a Novice Soccer group, and a Closed-skill Athlete group. There were two main findings. Firstly, both soccer groups performed better than the Closed-skill Athletes on speed and accuracy of motor execution. Secondly, there were no significant differences between Expert and Novice soccer players in the speed and accuracy of motor execution.     

On discontinuities in motor learning: a longitudinal study of complex skill acquisition on a ski-simulator

The qualitative behavioral reorganizations that occurred during the acquisition of a complex motor skill were examined. Five novice participants practiced for 39 sessions of ten 1-min trials on a modified version of the ski-simulator. Analyses focused on the motion of the apparatus platform, modeled as a self-sustained oscillator. At the beginning of the experiment, all participants adopted a behavior that could be modeled with a highly nonlinear stiffness function and a Rayleigh damping function. The behavior in the final part of the experiment was captured by a qualitatively different model, with a linear stiffness function and a van der Pol damping behavior. The transition from the initial to the final model was gradual and was marked in most cases by an abrupt increase of oscillation frequency. During the transition stage, the 2 damping behaviors seemed alternately exploited within each trial. The results are discussed in the framework of the dynamical systems approach to motor coordination and learning, considering motor skill acquisition as a phase transition.     

Speech and nonspeech sequence skill learning in adults who stutter

Two studies compared the speech and nonspeech sequence skill learning of nine persons who stutter (PWS) and nine matched fluent speakers (PNS). Sequence skill learning was defined as a continuing process of stable improvement in speed and/or accuracy of sequencing performance over practice and was measured by comparing PWS's and PNS's performance curves of accuracy, reaction time, and sequence duration, as well as retention and transfer. In experiment one, participants completed a 30-trial finger tapping sequence and in experiment two, a 30-trial read-aloud sequence of nonsense syllables. Significant between-group differences were found in the speed of sequencing performance after practice, and on retention and transfer tests. These results partially supported the inference that PWS demonstrated differences in early stages of sequence skill learning compared to PNS. EDUCATIONAL OBJECTIVES: As a result of this activity the participant will be able to: (1) define skill learning and the important indicators of skill learning; (2) summarize the reviewed literature concerning the performance of PWS on speech and nonspeech sequencing tasks over practice; and (3) explain the implication of reaction time differences over practice between PWS and PNS.     

Neurobiological degeneracy: Supporting stability,flexibility and pluripotentiality in complex motor skill

This paper investigated neurobiological degeneracy of the motor system that emerged as a function of levels of environmental constraint. Fourteen participants performed a breaststroke-swimming task that required them to develop a specific biomechanically expert pattern and in turn provide the basis for a suitable task vehicle to study the functional role of movement variability. Inter-limb coordination was defined based on the computation of continuous relative phase between elbow and knee oscillators. Unsupervised cluster analysis on arm–leg coordination revealed the existence of different patterns of coordination when participants achieved the same task goal under different levels of environmental constraints (i.e. different amounts of forward resistances). In addition, clusters differed in terms of higher order derivatives (e.g., joint angular velocity, joint amplitude), suggesting an effective role for degeneracy in learning by allowing the exploration of the key relationships between motor organization and interacting constraints. There is evidence to suggest that neurobiological degeneracy supports the potential for motor re-organization to enhance motor learning.     

Long-term retention of a motor skill: Implicit sequence knowledge is not retained after a one-year delay

Experimental work shows that some motor skills are retained well over a long delay and others are not. It is possible that motor tasks that are primarily implicit are retained over long intervals, whereas those with an explicit component are subject to more rapid forgetting. To test whether implicit motor skills are retained, 24 (experienced) participants were retested after a one-year delay for their retention of an implicit motor sequence. They had been trained on the sequence in a button-pushing task. Although the experienced participants responded faster than they had a year earlier, they showed no retention of the sequence compared to 24 participants who had received no training a year earlier, and no savings in relearning the sequence. The overall speed effect may indicate that the amount of training is crucial to the degree of retention of a skill. The results indicate that it is not the case that implicit motor skills are well retained whereas those with an explicit component are not.     

Analogy as relational priming: a developmental and computational perspective on the origins of a complex cognitive skill

The development of analogical reasoning has traditionally been understood in terms of theories of adult competence. This approach emphasizes structured representations and structure mapping. In contrast, we argue that by taking a developmental perspective, analogical reasoning can be viewed as the product of a substantially different cognitive ability - relational priming. To illustrate this, we present a computational (here connectionist) account where analogy arises gradually as a by-product of pattern completion in a recurrent network. Initial exposure to a situation primes a relation that can then be applied to a novel situation to make an analogy. Relations are represented as transformations between states. The network exhibits behaviors consistent with a broad range of key phenomena from the developmental literature, lending support to the appropriateness of this approach (using low-level cognitive mechanisms) for investigating a domain that has normally been the preserve of high-level models. Furthermore, we present an additional simulation that integrates the relational priming mechanism with deliberative controlled use of inhibition to demonstrate how the framework can be extended to complex analogical reasoning, such as the data from explicit mapping studies in the literature on adults. This account highlights how taking a developmental perspective constrains the theory construction and cognitive modeling processes in a way that differs substantially from that based purely on adult studies, and illustrates how a putative complex cognitive skill can emerge out of a simple mechanism.     

Assessment of fine motor skill in musicians and nonmusicians: differences in timing versus sequence accuracy in a bimanual fingering task

While professional musicians are generally considered to possess better control of finger movements than nonmusicians, relatively few reports have experimentally addressed the nature of this discrepancy in fine motor skills. For example, it is unknown whether musicians perform with greater skill than control subjects in all aspects of different types of fine motor activities. More specifically, it is not known whether musicians perform better than control subjects on a fine motor task that is similar, but not identical, to the playing of their primary instrument. The purpose of this study was to examine the accuracy of finger placement and accuracy of timing in professional musicians and nonmusicians using a simple, rhythmical, bilateral fingering pattern and the technology that allowed separate assessment of these two parameters. Professional musicians (other than pianists) and nonmusicians were given identical, detailed and explicit instructions but not allowed physically to practice the finger pattern. After verbally repeating the correct pattern for the investigator, subjects performed the task on an electric keyboard with both hands simultaneously. Each subject's performance was then converted to a numerical score. While musicians clearly demonstrated better accuracy in timing, no significant difference was found between the groups in their finger placement scores. These findings were not correlated with subjects' age, sex, limb dominance, or primary instrument (for the professional musicians). This study indicates that professional musicians perform better in timing accuracy but not spatial accuracy while executing a simple, novel, bimanual motor sequence.