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4. MOTOR SKILLS
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4.1 Studies ot Multitask Performance (Brown, McLeod)(Project No. 8)
Under what conditions can one do two things at once? The answer to this question is of theoretical significance since it has obvious implications for our understanding of attentional processes, and is of practical importance in job design. Brown (27) has reviewed dual-task techniques for measuring mental load, while McLeod has shown that a variety of auditory/vocal output tasks such as the identification of words and tones, or mental arithmetic, can be performed without interfering with the timing of a concurrent task involving manual responses to visual stimuli (112; 113). This has important implications for procedures currently used to measure mental load, since it implies that effects which have so far been attributed to central attentional limitations are crucially dependent on the particular responses required.
A novel method of measuring response interference has been developed which has thrown light on the age-old controversy of whether simultaneous independent motor responses are controlled sequentially or in parallel (114). Similarity of the muscular action required to execute responses on the two tasks appears to be a crucial factor. (113; 115)
4.2 Keyboards etc. (Dennett, Long, Nimmo-Smith)(Project No. 10)
This research has a wide brief and addresses problems as and when they arise from applied contexts, primarily from the Post Office. For example, Long (90; 94) evaluated the effect of delaying auditory and visual feedback occasioned by the introduction of buffer storage into a terminal. These studies led to the consideration of the function of visual feedback, for typing in isolation. Two priuary functions were observed (92): error correction (by means of sight of the printed copy) and referencing the hands (by means of sight of the keyboard). Other research is motivated by likely future needs rather than current problems; an example is the evaluation of a proximity or pointing device for the entry of numerical data by naive users as an alternative to the conventional keyboard (101).
Work is not restricted r.c keyboards or alternatives. Long, Dennett, Marcel and Wing have evaluated the effects on estimated waiting time in the context of telephone usage in future electronic networks of class of call, distance of the called party and dialling time (100; 206). Large effects of the first two factors were recorded.
Work by Logie, and Nimmo-Smith has included ihe development of statistical rjcasureraent techniques for evaluating skilled performance (102). Other work is expected to tccus on the needs of the very naive user in interactive data retrieval systems (94).
4.3 Handwriting (Baddeley, Wing)
Research by Wing has focused on both the movement control aspect and the more linguistic aspects of writing. There has been computer programme development for the purposes both of collecting precise and detailed information on the skill of writing, and also for the storage and subsequent analysis of large amounts of data. Dutch workers have already demonstrated the importance of timing control in handwriting. A model of timing control of successive strokes in handwritten letters has been developed on the basis of data collected from extensively practised subjects writing single letters (204; 205; 207). This is currently being extended to the analysis of timing control in writing words, where contextual factors become an important factor. Since both left and right handers are included in the sample, it is hoped to investigate gross differences in cerebral organisation.
At a more applied level, we are exploring the use of handwriting as an index of motor performance which may be sensitive to stress; both alcohol (209) and Sleep loss have so far been shown to affect handwriting (53). Other applied problems include the constraints often placed on the writer in filling in forms where the requirement to write in specified locations has been shown to impair performance (208).
Work on slips of the pen by Wing and Baddeley (210) has shown the distribution of errors is not random throughout the sentence, the distribution of such slips being different from that of spelling errors. Further analyses of a corpus of material stored by computer are now under way to throw light on the mechanisms underlying the production of such slips.