Support for an explanation of the guidance effect in motor skill learning.

The authors investigated whether the knowledge of results (KR) schedule influences the extent to which intrinsic feedback is noticed and used. Fifty-six participants received KR that was either delayed over 2 trials (Delay-2) or provided directly after each trial (Delay-0) during 160 trials of an unfamiliar aiming task. No-KR retention tests were given after 80 trials and 1 min and 24 hr after the end of acquisition. After retention, all participants were questioned about their use of intrinsic feedback during practice and whether those sources changed as a function of practice. The Delay-2 group performed significantly less accurately on the 1st and last blocks of acquisition trials but showed a significantly smaller performance decline from acquisition to retention. Moreover, the Delay-2 group noticed and used a greater variety of intrinsic feedback sources and its members were more likely to report that their usage changed with practice.

The flip side of perception-action coupling: locomotor experience and the ontogeny of visual-postural coupling.

The possible role of motor development on psychological function is once again a topic of great theoretical and practical importance. The revival of this issue has stemmed from a different approach to the topic, away from Gesell's interest in the long-term prediction of psychological functions from early motoric assessments, toward an attempt to understand how the acquisition of motor skills orchestrates psychological changes. This paper describes how the acquisition of one motor skill, prone locomotion, has been linked to developmental changes in an infant's ability to regulate posture based on information available in patterns of optic flow. It is argued that the onset of prone locomotion presses the infant to differentiate spatially delimited regions of optic flow to effectively and efficiently control the important subtasks nested within the larger task of locomotion, namely, steering, attending to the surface of support, and maintaining postural control. Following this argument, a research program is described that aims to determine if locomotor experience is causally linked to improvements in the ability to functionalize peripheral optic flow for postural control or whether locomotor experience is merely a maturational forecaster of such improvements. Finally, a hypothesis is put forward that links the emergence of wariness of heights to infants' ability to regulate posture on the basis of peripheral optic flow. The paper's overarching theoretical point is the principle of probabilistic epigenesis, which states that one developmental acquisition produces experiences that bring about a host of new developmental changes in the same and different domains.

Motor learning as a function of KR schedule and characteristics of task-intrinsic feedback.

Forty participants (age range = 18-35 years) practiced 1 of 2 versions of an aiming task (with or without spring resistance). Knowledge of results (KR) was provided to them either immediately or after a delay of 2 trials. Immediate KR led to significantly more accurate performance during the 80 trials in acquisition but significantly less accurate performance on a 40-trial retention test given 24 hr after practice. In addition, the spring version of the task was performed significantly less accurately than the no-spring version on the 24-hr retention test. Most important, a significant interaction on the 24-hr retention test revealed that performance of the no-spring version of the task, when KR had been given after a 2-trial delay, was significantly more accurate than performance of the other 3 combinations of task version and KR schedule. The results suggest that KR dependency in motor skill learning is related to familiarity with task-intrinsic feedback in addition to the schedule on which KR is presented.

Motor performance with a simulated artificial limb.

The present study was conducted to examine performance differences on a reaching and grasping task related to an activity of daily living. This involved either the anatomical limb or a simulated artificial limb. College-aged volunteers (2 men and 4 women), one of whom was left-handed, performed the reaching and grasping task. The apparatus, placed on a table before the seated participant, was a square wooden board which contained a starting key and holes for the insertion and removal of a small Fiberglas dowel. At the beginning of the trial the participant depressed the start key, reached forward and grasped the dowel, and then returned the dowel to a finishing hole located directly in front of the start key. The results of 2 (side) x 2 (type of limb) repeated-measures multivariate analyses of variance on the mean and standard deviation of the movement times showed a significant main effect for type of limb (Wilks lambda 3,3 = .047 and .079, respectively, p < .05). Analyses of variance on mean total transport time, extension time, flexion time, and their standard deviations showed that times were slower and less consistent with the prosthesis for all measures. These results and those of later research should be focused on the development of training principles for both therapists and individuals with an amputation. In addition, the simulated prosthesis is an excellent experimental model for basic and clinical research in the control and acquisition of coordinated movement.

The discrimination, acquisition, and retention of aiming movements made with and without elastic resistance.

Two experiments were conducted to compare the discrimination, acquisition, and retention of movements made with and without elastic resistance. Using methods from psychophysics, Experiment 1 revealed that a discrete 800-mm movement could be discriminated equally precisely when it was performed with and without elastic resistance. Similarly, there was no difference in the spatial accuracy of a discrete aiming movement made with and without elastic resistance when extended practice with knowledge of results (KR) was provided in Experiment 2. Contrary to expectation, when KR about the outcome of the movement was removed on a retention test given 24 h after practice, the accuracy of the movements made with elastic resistance declined much more rapidly than those made without resistance. These findings question the common assumption that elastic resistance is a desirable characteristic of a control mechanism. Actual or potential applications of this research include the design of control mechanisms that facilitate performance under a variety of task and environmental conditions.

Salmonella typhimurium cob mutants are not hyper-virulent.

It was previously reported that Salmonella typhimurium LT2 cob mutants defective in the biosynthesis of vitamin B12 (cobalamin) are more virulent than the wild type in mice. Here we show that the strains used previously are non-isogenic and that the proposed increase in virulence of the cob mutant strain results from an uncharacterized mutation in the "wild type" which attenuates virulence, most likely by decreasing expression of the spv genes on the virulence plasmid. As a result the cob mutant will appear as hyper-virulent. Examination of the virulence of reconstructed wild-type and cob mutant strains showed that their growth rates were similar in mice, and we conclude that vitamin B12 does not affect the virulence of S. typhimurium LT2.

The contextual interference effect in parameter modifications of the same generalized motor program.

This study extended previous work (Sekiya, Magill, Sidaway, & Anderson, 1994) by examining whether the contextual interference (CI) effect could be found when task variations were controlled by the same generalized motor program (GMP) but differentiated on the basis of overall force parameter modifications. A subsidiary aim of this study was to determine how the amount of practice influenced the CI effect. During 2 acquisition sessions and 2 retention sessions, participants (N = 24) performed 3 task variations in either a blocked (low CI) or serial (high CI) condition. The task variations shared the same relative force structures but differed in the amount of overall force that had to be produced. Analysis of a general error measure revealed a strong CI effect, indicating that overall force parameter modifications of the same GMP created the CI effect. Analyses of various dependent measures, which dissociated GMP from parameter components with regard to force characteristics, revealed that parameter learning, but not GMP learning, was enhanced by high CI practice. No CI effect occurred in any aspect of timing characteristics. The amount of practice used in the present study did not influence the efficacy of the CI effect.

The contextual interference effect for skill variations from the same and different generalized motor programs.

Magill and Hall (1990) hypothesized that the contextual interference (CI) effect is found only when task variations to be learned are governed by different generalized motor programs (GMPs). The present experiments examined their hypothesis by requiring subjects to learn variations of a tapping task that had either different (Experiment 1) or the same (Experiment 2) relative timing structure. In each experiment, subjects (N = 36) performed 270 acquisition trials with knowledge of results (KR) in either a blocked or a serial order. One day later, subjects performed 30 retention trials without KR. In data analyses, errors due to parameter modifications were dissociated from errors due to GMP construction to examine which process was responsible for the CI effect. In both experiments, parameter learning created a CI effect while GMP learning failed to produce a CI effect. In the light of these findings, a modification is proposed to the Magill and Hall (1990) hypothesis that takes into account these distinct processes in motor learning.

Coordination changes associated with practice of a soccer kick.

The purpose of this study was to examine the changes in coordination associated with practice of a soccer kick. Video records were collected on 6 novice, right-footed soccer players prior to and after 20 regularly scheduled kicking practice sessions. Three experienced players were also videotaped for comparison. Movement of the right leg was digitized and analyzed using motion analysis software. As a result of practice, subjects were able to significantly increase the maximum resultant linear velocity of the foot, and these increases were accompanied by changes in the pattern of coordination underlying the movement. These changes were assessed qualitatively through the topological characteristics of the relative motions of the hip and knee and quantitatively through three different timing variables. The results provide some support for Bernstein's (1967) ideas on the acquisition of skilled behavior as well as for the two-stage model of motor learning proposed by Newell (1985).

Hospital nurses' valuation of quality assurance.

Nurses responsible for quality assurance in ten metropolitan hospitals surveyed nurses from their institutions in an attempt to understand sluggish interest in quality assurance activities. The registered nurses surveyed agreed that involvement in quality assurance is an important part of the professional nurse's role, but this belief did not often translate into positive attitudes toward nor participation in quality assurance activities.