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.

Summary. A random sample of right‐handed children and a population sample of left‐handed children, including over 100 subjects in each group, were assessed for vocabulary, drawing, maze tracing and for laterality of hand, eye and foot. Reading quotients were available for 145 children. The data were examined in two ways. The first compared the abilities of laterality groups over the total sample and found no significant differences. The second assessed the laterality of children at the lower extreme of the ability distribution and found a slight excess of left handers. A brief survey of the literature shows that a distinction between studies according to their resemblance to these two analyses could help to account for the coexistence of positive and negative findings. Possible causes of the excess of children with sinistral tendencies in groups selected for educational disabilities are discussed with special reference to a theory of the determination of handedness (Annett, 1972) which permits a restatement of the maturational lag hypothesis of developmental language delay.

No abstract

Process control teaks typically require the operator to diagnose and rectify failures on tho basis of parameters measured at different points in the plant and centrally displayed on a control panel. An i nvoat.igat.ion was carried out to discover what form of technical introduction would be most successful in training an operator accurately to recognize faults practised during training, and in addition provide a strategy enabling tho trainee to Book out relevant information in order to diagnose unfamiliar faults.Throe groups of subjects were trained using an adaptive cumulative-part technique to recognize eight fuulte displayed on a simulated control panel. Each group received a different introduction to the plant: (i) the t Theory' group were given it conventional description of the t Plant' and its functions; (ii} tho' Rules I group in addition were taught a sot of rules that would assist them in inferring failures from the panel array; (iii) the' No Story' group underwent training without any prior theoretical i.ntroduction.After cumulative-part training ell three groups performed equally well on the eight faults. However, the' Rules ' group were consistently the most proficient at diagnosing' unfamiliar' faults. Although tile' Theory' group initially were more able at recognizing' unfamiliar' faults, after intensive training their performance bud deteriorated to a level not significantly different from the I No Story' group.It is argued, therefore, that in an effective traini.ng regime, tho teaching of conventional 'Theory' alone is of limited value, and for versatile diagnostic performance, training should include generalizable rules of the kind described in this paper.