Spencer J. Hayes

Goal-Directed Aiming: Two Components but Multiple Processes

This article reviews the behavioral literature on the control of goal-directed aiming and presents a multiple-process model of limb control. The model builds on recent variants of Woodworths (1899) two-component model of speed-accuracy relations in voluntary movement and incorporates ideas about dynamic online limb control based on prior expectations about the efferent and afferent consequences of a planned movement. The model considers the relationship between movement speed and accuracy, and how performers adjust their trial-to-trial aiming behavior to find a safe, but fast, zone for movement execution. The model also outlines how the energy and safety costs associated with different movement outcomes contribute to movement planning processes and the control of aiming trajectories. Our theoretical position highlights the importance of advance knowledge about the sensory information that will be available for online control and the need to develop a robust internal representation of expected sensory consequences. We outline how early practice contributes to optimizing strategic planning to avoid worst-case outcomes associated with inherent neural-motor variability. Our model considers the role of both motor development and motor learning in refining feed-forward and online control. The model reconciles procedural and representational accounts of the specificity-of-learning phenomenon. Finally, we examine the breakdown of perceptual-motor precision in several special populations (i.e., Down syndrome, Williams syndrome, autism spectrum disorder, normal aging) within the framework of a multiple-process approach to goal-directed aiming.

What is modelled during observational learning

Abstract In this article, we examine the question of what information is processed during observational learning by evaluating a variety of methods, theories, and empirical data. Initially, we review work involving neuroimaging techniques and infant imitation. We then evaluate data from behavioural experiments involving adults, wherein a variety of attempts have been made to isolate the critical or minimal information constraining the acquisition of coordination. This body of research has included comparisons between video and point-light displays, manipulations to the amount and type of information presented in the display, the collection of point-of-gaze data, and manipulations to the task context in terms of outcome goals. We conclude that observational learning is governed by specific features of the models action (i.e. motions of the end effector) and the task (i.e. outcome constraints) and, in contrast with traditional theoretical modelling, more global aspects of a model (i.e. the relative motions within and between joints) do not appear to be the primary method for constraining action execution.

Changes in coordination, control and outcome as a result of extended practice on a novel motor skill

It has been proposed that, when learning a motor skill, individuals initially freeze degrees of freedom to simplify control. There is limited empirical evidence to support this proposition. We examined this issue by monitoring the performance of a non-skilled individual learning a soccer chip shot with his non-dominant leg over 9 days of practice (425 trials). Principal component analysis was used to examine dimensional change. The most dramatic change occurred at the hip, with the range of motion decreasing during the first 5 days of practice and then increasing thereafter. A reverse pattern was observed at the knee and ankle. While showing a progression in control from proximal to distal, a further phase was observed where primary control was passed back to the hip. The degree of linear coupling between the joints also increased with practice until day 5, after which independent control was observed. The number of controlled dimensions did not change across practice. Radial error decreased over practice and kinematics relating to the hip were most predictive of error, especially early in practice. Freezing degrees of freedom was a strategy implemented across the first half of practice, after which point-independent control was gradually restored enabling successful consistent performance.

General motor representations are developed during action-observation

This study was designed to examine the generality of motor learning by action-observation. During practice, action-observation participants watched a learning model (e.g., physical practice participants) perform a motor sequence-timing task involving mouse/cursor movements on a computer screen; control participants watched a blank screen. Participants transferred to either a congruent (same mouse-cursor gain), or an incongruent (different mouse-cursor gain) condition. As predicted, motor sequence timing was learned through action-observation as well as physical practice. Moreover, transfer of learning to an incongruent set of task demands indicates that the motor representation developed through observation includes generalised visual-motor procedures associated with the use of feedback utilization.

Action representations in perception, motor control and learning: implications for medical education.

Medical Education 2011: 45: 119–131

The efficacy of demonstrations in teaching children an unfamiliar movement skill: The effects of object-orientated actions and point-light demonstrations

Abstract In Experiment 1, adult and child participants were instructed to imitate a video model performing a bowling action with or without a ball. Participants imitated the action with greater accuracy without a ball and in general adults were more accurate than children. In Experiment 2, adults and children were shown a video or point-light display of the bowling action. There was no difference in movement form between the adult point-light and video groups. In contrast, children were poorer at reproducing the action when viewing point-light compared with video sequences (P < 0.05). The novel point-light display hindered the childrens ability to provide conceptual mediation between the presented information and action requirements. In Experiment 3, a child point-light group was provided with perceptual-cognitive training. The perceptual-cognitive training group demonstrated better movement reproduction than a group who viewed the point-light displays with no training (P < 0.05), although there were no differences between participants who received training and those who viewed a video. Children are able to perceive and use relative motion information from a display after some general training, and the effectiveness of demonstrations needs to be judged relative to the task context.

Demonstration as a rate enhancer to changes in coordination during early skill acquisition

Abstract We compared the nature and rate of change in intra-limb coordination in participants who observed a video model (model) with those who practised based on verbal guidance only (control). Sixteen male novices threw a ball towards a target with maximal velocity using a back-handed, reverse baseball pitch. Participants in the model group immediately changed their intra-limb relative motion to more closely resemble the models relative motion pattern. This new coordination pattern, and concomitant changes in ball speed, was maintained throughout acquisition, without further change. In contrast, the control group showed no change in coordination or ball speed across acquisition. Our findings suggest that demonstrations act as a rate enhancer, conveying an immediate movement solution that is adopted early in acquisition. A model may constrain the learner to perceive and imitate the models relative motion pattern as suggested by Scully and Newell (1985). The stability of this new movement pattern questions accounts of learning, which suggest that prescriptive, directed learning may result in the “soft assembly” of an inaccurate and temporary movement solution.

Eye movements are not a prerequisite for learning movement sequence timing through observation

The present experiment examined learning of a three-segment movement sequence using physical or observational practice, and whether permitting eye movements to be made during observation is a prerequisite for learning such a movement sequence. Specifically, participants were required to move a mouse cursor through a three-segment movement sequence in order to satisfy one of three movement time goals (800, 1000, 1200 ms). A yoked-participant design was used in which a physical practice group acted as a learning model, which was viewed simultaneously by two groups that carried out different observational practice procedures. An observation group was permitted to move their eyes whilst observing the model, whereas the fixation group was instructed to maintain fixation on a central target. The difference between pre-test and post-test data indicated that all the three experimental groups significantly altered their timing accuracy, variability and movement kinematics over practice, while the control groups behaviour was unchanged. These data indicate that movement time as well as the underlying movement control was learned following observation of a movement with or without an explicit contribution from eye movements, albeit to a lesser extent during the final segment of the sequence when compared to the physical practice group. The implication is that while similar processes might normally be involved in physical and observational practice, information afforded by eye movements during observation (e.g., efference copy and eye proprioception) is not necessary for movement sequence learning.

Scaling a motor skill through observation and practice

The authors examined the proposal that a motor skill is scaled through physical practice and not through observation of a model. In 4 groups, participants (N = 32) did or did not imitate a model bowling a ball to a target 8 m away. In an assessment phase, those groups did or did not observe the same model bowling a ball to a target 4 m away. Participants who viewed a model in the assessment phase were more accurate and consistent in terms of bowling accuracy than were those who did not. Their shoulder and wrist velocity profiles were more similar to those of the 4-m model than were those of the no-model group. Participants who had previous practice and viewed a demonstration were more accurate at scaling the wrist of the bowling arm. Observing a demonstration facilitates the acquisition of control-related features of a movement. Furthermore, early acquisition of coordination aids the use of velocity information for scaling the endpoint of the primary effector.

Between-person effects on attention and action: Joe and Fred revisited

Previous study indicates that target–target inhibition of return (IOR) is not restricted to a single nervous system. Specifically, watching another person perform a goal-directed aiming movement engages similar inhibitory processes on a subsequent aiming attempt as if having performed the preceding movement oneself. This between-person effect has been attributed to the mirror neuron system. In the study reported here, we replicated this finding and examined the relative importance of automatic stimulus alerting events and action–observation by dissociating these two influences. This was done by having two people alternately perform sets of two aiming trials to the same equally probable targets. Under some experimental conditions, one or both of the performers moved to a non-illuminated target. In this way, we dissociated the stimulus and observed event under some between-person conditions. Although IOR was greatest when the stimulus and observed events were compatible, both contributed to the between-person inhibitory processes slowing the responses (Experiment 1). The impact of observing another person perform an aiming movement appears to have more to do with realizing a particular spatial goal than seeing the biological motion associated with achieving that goal (Experiment 2). Findings that both the illumination of a visual target signal and the observation of another person’s action engage similar attention–action processes are consistent with action-based accounts of visual selective attention.