John Annett

The control of movement in the preferred and non-preferred hands.

The nature of the difference in skill between the preferred and non-preferred hands was investigated using a peg-board task. The first experiment examined the effects of varying movement amplitude and target tolerance on performance. The difference between hands was found to be related to tolerance rather than movement amplitude. The second study analysed a film record of well-practised subjects, confirming the hypothesis that most of the difference between hands is due to relative slowness of the non-preferred hand in the positioning phase involving small corrective movements. Analysis of the type and number of errors further suggested that this result is not due to differences in duration of movements but to their increased frequency, implying greater accuracy of aiming with the preferred hand. Thus whilst the initial gross analysis implicated feedback processing in skill differences the more detailed analysis suggests that motor output of the nonpreferred hand is simply more variable.

Motor imagery: Perception or action?

Motor imagery has been studied using subjective, behavioural and physiological methods and this paper reviews theoretical and practical issues from all three viewpoints. Attempts to measure motor imagery on a subjective scale have met with limited success but alternative methods are proposed. Research on mental practice suggests a number of different processes may be needed to explain the variety and variability of effects obtained. Recent studies of spatial and motor working memory signify the importance of a primarily visuo-spatial component in which actions are consciously represented together with a more properly motoric component which must be activated to generate either images or overt actions. Finally the question of whether motor imagery is primarily perceptual or motoric in character does not have a simple neurophysiological answer due to the highly distributed nature of motor control. Nevertheless some of the key mechanisms serving both spatial and motoric components have been provisionally identified.

Subjective rating scales: science or art?

Subjective rating scales are widely used in almost every aspect of ergonomics research and practice for the assessment of workload, fatigue, usability, annoyance and comfort, and lesser known qualities such as urgency and presence, but are they truly scientific? This paper raises some of the key issues as a basis for debate. First, it is argued that all empirical observations, including those conventionally labelled as ‘objective’, are unavoidably subjective. Shared meaning between observers, or intersubjectivity, is the key criterion of scientific probity. The practical steps that can be taken to increase intersubjective agreement are discussed and the well-known sources of error and bias in human judgement reviewed. The role of conscious experience as a mechanism for appraising the environment and guiding behaviour has important implications for the interpretation of subjective reports. The view that psychometric measures do not conform to the requirements of truly ‘scientific’ measurement is discussed. Human judgement of subjective attributes is essentially ordinal and, unlike physical measures, can be matched to interval scales only with difficulty, but ordinal measures can be used successfully both to develop and test substantive theories using multivariate statistical techniques. Constructs such as fatigue are best understood as latent or inferred variables defined by a set of manifest or directly observed indicator variables. Both construct validity and predictive validity are viewed from this perspective and this helps to clarify several problems including the dissociation between measures of different aspects of a given construct, the question of whether physical (e.g. physiological) measures should be preferred to subjective measures and whether a single measure of constructs which are essentially multidimensional having both subjective and physical components is desirable. Finally, the fitness of subjective ratings to different purposes within the broad field of ergonomics research is discussed. For testing of competing hypotheses concerning the mechanisms underlying human performance, precise quantitative predictions are rarely needed. The same is frequently true of comparative evaluation of competing designs. In setting design standards, however, something approaching the level of measurement required for precise quantitative prediction is required, but this is difficult to achieve in practice. Although it may be possible to establish standards within restricted contexts, general standards for broadly conceived constructs such as workload are impractical owing to the requirement for representative sampling of tasks, work environments and personnel.

A method for measuring team skills

A method for identifying and measuring team skills, specifying team training objectives and the objective assessment of team performance is described. First, a theoretical model of team performance is outlined and then a version of Hierarchical Task Analysis specially adapted to analysing team tasks is described. The two are then combined into an event-related measurement scheme, which provides a set of objective criteria by which key team skills can be assessed. The method is illustrated by an example from a basic Anti-Submarine Warfare training exercise which forms part of the Principal Warfare Officers course at the Royal Naval School of Maritime Operations. The potential of the method is discussed, including the opportunities it may provide for the standardization of team performance assessment and in the use of new technology in the partial automation of shore-based and ship-board team training.

Handedness for Eating in Gorillas

Observations of spontaneous reaching for food in 31 captive lowland gorillas found a full range of hand preferences between strong left and strong right, with most animals showing intermediate levels of preference. There was a high degree of consistency between observations made on different occasions for the same animal, showing that degrees of relative preference tend to be stable in individuals. The findings agree with the majority of previous studies of apes and other primates in showing no species bias to one side, with about half the animals left and half right preferent.

The learning of motor skills: sports science and ergonomics perspectives

The paper describes some of the common origins of ergonomics and sports science in the UK with particular reference to research on motor learning. Attention is drawn to the value of analytical methods developed by ergonomists in deriving training prescriptions and their relationship with conventional learning theory is discussed. The cognitive revolution, which in the last 25 years has changed the face of psychology, has also had its impact on ergonomics and basic research on motor skills. The role of cognitive processes in motor learning is being reassessed and there is a renewed interest in topics such as verbal instruction, imitation, imagery, and mental practice which to earlier generations of behavioural scientists appeared beyond the scope of scientific investigation. The paper outlines some recent research into the role of imagery in motor learning illustrating these new approaches.

A note on the validity and reliability of ergonomics methods

The view that, by analogy, ergonomics methods should be subject to the same requirements of validity and reliability as are demanded of psychometric tests is shown to be an oversimplification. Two broad classes of method are distinguished. Analytic methods aim to produce a better understanding of the processes affecting complex human-machine systems, whilst evaluative methods are limited to the measurement of specific variables. The analogy with psychometrics applies to the latter type but is less appropriate to the former. Analytic methods depend heavily on the application of currently accepted theories of performance. Empirical data may be variable, but the expertise of the analyst may be more to blame than the method as such.

Transfer of Training: A Review of Research and Practical Implications

Abstract Some of the issues of broad‐based training, which is aimed at promoting transferability of skill, are examined and related to the concept of transfer of training. The classical research findings on transfer are summarized and some implications for training policy are drawn. The concept of transfer is re‐examined in the light of recent ideas in cognitive psychology and the psychology of individual differences, and suggestions are made for training methods which could be expected to enhance transfer and hence transferability. Finally, attention is drawn to problems to which future research should be addressed.

Recalling Demonstrated and Guided Movements Using Imaginary and Verbal Rehearsal Strategies

This study investigated the recall of movement patterns presented either by demonstration or guided movement with vision eliminated. Participants were instructed to rehearse and remember each of the 12 patterns using one of four strategies: imagery, verbal labeling, imagery and verbal labeling, or no rehearsal strategy (i.e., control condition). Recall was better for patterns that were demonstrated than for those presented via guided movement. In addition, more patterns were remembered if a combination of imagery and verbal labeling were employed as a rehearsal strategy compared to using imagery alone. These results are discussed using Annetts (1994) model showing the relationships between action, language, and imagination in the acquisition of motor skills.

Subjective rating scales in ergonomics: a reply

Comments on the target paper are acknowledged. Whilst there is still some concern that subjective rating scales are scientifically suspect, the general view is that verbal reports, including ratings, constitute objective data, which can be of considerable value in ergonomics research and practice. The main anxiety attached to their use is to ensure acceptable levels of reliability and validity. Quantification in the strict sense can be achieved by some measures but is by no means essential for all scientific and practical purposes. The value of ordinal and qualitative data obtained by subjective judgements should not be underestimated, especially in predicting future performance. Many commonly used constructs such as fatigue, stress, mental workload, usability, etc. are complex and multidimensional, often combining both ‘subjective’ and ‘objective’ measures. The validity of individual dimensions and complex constructs lies principally in their relationships with other variables of interest in the context of the specific investigation. The question of design standards based partly or wholly on such scales should therefore be treated with some caution.