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Derek Ashford

Publications and source records attributed to Derek Ashford.

4 recordsLinked to original sources

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 (delta(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 (delta(u)Bi = 1.62 and 0.61, respectively, for MD and MO). There were slightly reduced effects for continuous tasks (delta(u)Bi = 1.01 and 0.51, respectively, for MD and MO) and smaller to medium-sized effects for discrete tasks (delta(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.

Attention↗

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.

Adult↗

Intermittent vision and one-handed catching: the temporal limits of binocular and monocular integration.

The aim of this research was to examine the temporal limits of binocular and monocular integration useful for one-handed catching. Participants performed 20 one-handed catching trials in 12 conditions (N = 240) defined according to the type of viewing (binocular, monocular) and the manipulation of the visual sample (continuous, intermittent). Catching performance deteriorated significantly when there was no visual information available for 80 ms between 20-ms visual samples provided simultaneously to each eye. However, there was no change in catching performance when continuous monocular vision was available for 80 ms between the binocular samples. Performance under monocular viewing decreased significantly when intermittent samples were separated by less than 20 ms. These results confirm that the equivocality in previously reported temporal limits of binocular integration is due to the different arrangement of the intermittent vision conditions and hence the information available between intermittent samples.

Adult↗

Effect of verbal instructions and image size on visual search strategies in basketball free throw shooting.

We assessed the effects on basketball free throw performance of two types of verbal directions with an external attentional focus. Novices (n = 16) were pre-tested on free throw performance and assigned to two groups of similar ability (n = 8 in each). Both groups received verbal instructions with an external focus on either movement dynamics (movement form) or movement effects (e.g. ball trajectory relative to basket). The participants also observed a skilled model performing the task on either a small or large screen monitor, to ascertain the effects of visual presentation mode on task performance. After observation of six videotaped trials, all participants were given a post-test. Visual search patterns were monitored during observation and cross-referenced with performance on the pre- and post-test. Group effects were noted for verbal instructions and image size on visual search strategies and free throw performance. The 'movement effects' group saw a significant improvement in outcome scores between the pre-test and post-test. These results supported evidence that this group spent more viewing time on information outside the body than the 'movement dynamics' group. Image size affected both groups equally with more fixations of shorter duration when viewing the small screen. The results support the benefits of instructions when observing a model with an external focus on movement effects, not dynamics.

Adult↗