Derek Ashford

Observational modeling effects for movement dynamics and movement outcome measures across differing task constraints : A meta-analysis

The authors conducted a meta-analysis of the observational modeling literature to quantify overall between-participants treatment effects obtained when movement behaviors are acquired. Effects were obtained and reported separately for movement dynamics (MD) and movement outcome (MO) measures. The overall mean observational modeling treatment effects (δ u Bi ) were 0.77 and 0.17, respectively, for MD and MO measures. The effects reflected a significant advantage of observational modeling over practice-only control conditions. Most important, the magnitude of the obtained effects was far stronger for MD than for MO measures, confirming a distinctive response to observational modeling during motor learning. The advantage for MD measures over observational modeling measures was replicated for different types of tasks. Observational modeling was particularly beneficial for serial tasks (δ u Bi = 1.62 and 0.61, respectively, for MD and MO). There were slightly reduced effects for continuous tasks (δ u Bi = 1.01 and 0.51, respectively, for MD and MO) and smaller to medium-sized effects for discrete tasks (δ u Bi = 0.56 and 0.10, respectively, for MD and MO). The authors discuss those findings with reference to the visual perception perspective on observational modeling, i.e., that demonstrations primarily convey relative motions required to approximate modeled movement behaviors.

Effects of manipulating relative and absolute motion information during observational learning of an aiming task.

In the visual perception perspective of observational learning, the manipulation of relative and absolute motion information in visual demonstrations optimally directs learners’ search towards appropriate task solutions. We assessed the effect of emphasizing transformational information and removal of structural information using point-light kinematic displays in approximating the model’s relative motion patterns. Participants viewed computer-simulated point-light demonstrations or normal video demonstrations before and intermittently throughout 100 acquisition trials with knowledge of results on an underarm modified-dart aiming task. On the next day, all participants performed 20 retention trials without demonstrations. The kinematics of spatial and temporal coordination and control variables were examined relative to the model’s action, as well as performance scores. The results indicated that approximation of the model’s spatial and temporal coordination and control patterns was achieved after observation of either type of demonstrations. No differences were found in movement outcomes. In a second experiment, the effects of manipulating absolute motion information by slowmotion demonstrations were examined relative to real-time demonstrations. Real-time demonstrations led to a closer approximation to the model’s spatial and temporal coordination patterns and better outcome scores, contradicting predictions that slow-motion displays convey intact relative motion information. We speculate that the effect of visual demonstration speed on action perception and reproduction is a function of task constraints ‐ that is, novelty or familiarity of relative motion of demonstrated activities.

The Role of Textured Material in Supporting Perceptual-Motor Functions

Simple deformation of the skin surface with textured materials can improve human perceptual-motor performance. The implications of these findings are inexpensive, adaptable and easily integrated clothing, equipment and tools for improving perceptual-motor functionality. However, some clarification is needed because mixed results have been reported in the literature, highlighting positive, absent and/or negative effects of added texture on measures of perceptual-motor performance. Therefore the aim of this study was to evaluate the efficacy of textured materials for enhancing perceptual-motor functionality. The systematic review uncovered two variables suitable for sub-group analysis within and between studies: participant age (groupings were 18–51 years and 64.7–79.4 years) and experimental task (upright balance and walking). Evaluation of studies that observed texture effects during upright balance tasks, uncovered two additional candidate sub-groups for future work: vision (eyes open and eyes closed) and stability (stable and unstable). Meta-analysis (random effects) revealed that young participants improve performance by a small to moderate amount in upright balance tasks with added texture (SMD = 0.28, 95%CI = 0.46–0.09, Z = 2.99, P = 0.001; Tau2 = 0.02; Chi2 = 9.87, df = 6, P = 0.13; I2 = 39.22). Significant heterogeneity was found in, the overall effect of texture: Tau2 = 0.13; Chi2 = 130.71, df = 26, P<0.0001; I2 = 85.98%, pooled samples in upright balance tasks: Tau2 = 0.09; Chi2 = 101.57, df = 13, P<0.001; I2 = 72.67%, and in elderly in upright balance tasks: Tau2 = 0.16; Chi2 = 39.42, df = 5, P<0.001; I2 = 83.05%. No effect was shown for walking tasks: Tau2 = 0.00; Chi2 = 3.45, df = 4, P = 0.27, I2 = 22.99%. Data provides unequivocal support for utilizing textured materials in young healthy populations for improving perceptual-motor performance. Future research is needed in young healthy populations under conditions where visual and proprioceptive information is challenged, as in high-speed movements, or where use of equipment mediates the performer-environment interaction or where dysfunctional information sources ‘compete’ for attention. In elderly and ailing populations data suggests further research is required to better understand contexts where texture can facilitate improved perceptual-motor performance.

Intermittent Vision and One-Handed Catching: The Effect of General and Specific Task Experience

In Experiment 1, 15 skilled and 15 less skilled participants performed 1-handed catching in 4 conditions. For both groups, catching performance deteriorated significantly when no visual information was available for 40 ms between 20-ms visual samples (20/40) and continued to decline with subsequent increases in the duration between visual samples (i.e., 20/80 and 20/120). In Experiment 2, 50 participants performed a pretest and a posttest in a 20/80 condition, separated by 4 blocks of practice (N = 80). Participants who practiced with intermittent vision (20/40, 20/80, and 20/120) exhibited a significant improvement between pretest and posttest. Although general practice with intermittent vision enabled some adaptation, posttest performance did not equal performance in the 1st block of continuous vision.

Difference-based meta-analytic procedures for between-participant and/or within-participant designs: A tutorial review for sports and exercise scientists

Abstract The aim of this paper is to provide a contemporary summary of statistical and non-statistical meta-analytic procedures that have relevance to the type of experimental designs often used by sport scientists when examining differences/change in dependent measure(s) as a result of one or more independent manipulation(s). Using worked examples from studies on observational learning in the motor behaviour literature, we adopt a random effects model and give a detailed explanation of the statistical procedures for the three types of raw score difference-based analyses applicable to between-participant, within-participant, and mixed-participant designs. Major merits and concerns associated with these quantitative procedures are identified and agreed methods are reported for minimizing biased outcomes, such as those for dealing with multiple dependent measures from single studies, design variation across studies, different metrics (i.e. raw scores and difference scores), and variations in sample size. To complement the worked examples, we summarize the general considerations required when conducting and reporting a meta-analysis, including how to deal with publication bias, what information to present regarding the primary studies, and approaches for dealing with outliers. By bringing together these statistical and non-statistical meta-analytic procedures, we provide the tools required to clarify understanding of key concepts and principles.

Integration of Intermittent Visual Samples Over Time and Between the Eyes

The authors investigated the integration of alternate disparate monocular inputs for binocular perception in 1-handed catching experiments (N = 14, 32, 22, and 15 participants, respectively in Experiments 1-4). They varied the no-vision interval between alternate monocular samples to measure catching performance, and they compared the alternating monocular conditions with binocular and monocular conditions with equal no-vision intervals. They found no evidence of a binocular advantage for one-handed catching in the alternating monocular conditions. Performance in monocular and alternating monocular conditions did not differ across no-vision intervals ranging from 0-80 ms and was particularly worse than performance in binocular viewing conditions when the no-vision interval was 40 ms or more. The authors argue that the dissimilarity between disparate monocular inputs created by the approaching object limited the integration of those inputs and subsequent binocular perception.