Right-hand Performance Research Articles

Sequential motor ability of left-handed inverted and non-inverted writers

Left-handed female subjects, categorized as using an inverted (LI) ( n=7) or non-inverted (LN) ( n=7) writing posture, were compared on performance of a motor task. Task parameters were manipulated to create four conditions varying in demand for sequential processing. Based on previously observed group differences in the direction and extent of hemispheric lateralization, non-inverted writers were predicated to exhibit superior left hand performance. An analysis of variance substantiated a performance superiority by the LN writers, however, post hoc analysis indicated the difference to exist only at the highest level of task difficulty. Analysis of right-hand performance revealed a significant group difference in favor of the LN writers and a group-by-sequential processing demand interaction. This interaction indicated that the decrement in performance of LI writers, relative to LN writers, increased systematically with increases in task demands for sequential processing. Since previous research indicated that inverted writers exhibit less hemispheric specialization of function, it is concluded that this bilateral representation is associated with an overall reduction in sequential processing ability.

The lateralized effects of concurrent cognitive and motor performance.

Subjects were required to simultaneously tap two button switches, at two different distances apart, while at the same time performing a running memory span (RMS) task of either words or faces. Performance on the button-pressing task was assessed in terms of both speed and consistency. When the switches were close together, both of these measures showed leftand right-hand performance to be selectively disrupted by concurrent performance of faces and words memory tasks, respectively. With the switches further apart, selective disruption of the contralateral hand occurred only with thespeed index. Using the consistency index, however, bilateral disruption was observed with both types of RMS tasks. Error and d’ performance on the words and faces RMS tasks was only disrupted by contralateral manual activity. Some implications of these results for neuropsychological models of brain lateralization of function are discussed.

The Influence of Brain Lateralization of Function on a Manual Skill

The present study considers the predictions of the brain lateralization of function hypothesis for the concurrent-task situation where the subject is required, to perform simultaneously a manual and a cognitive task. The manual task required the subject to successively press two keys with either the right or left hand, this being done concurrently with one of twelve different cognitive tasks. The cognitive tasks varied in terms of their verbal (left hemisphere) and non-verbal (right hemisphere) attributes. The results indicate that, for the concurrent verbal task conditions, only right-hand performance was disrupted while left-hand performance remained unchanged. For the non-verbal conditions both left and right hand performance was disrupted. These findings were interpreted in terms of brain lateralization of cognitive functions and possible hemispheric processes controlling manual performance.

A developmental study of the influence of cognitive activity on an ongoing manual task

The present study investigated developmental changes in the lateralized effects of concurrent cognitive activity on the performance of a manual task. Children aged 9, 10, 11 and 12 years were required to press a key continuously for 15 sec whilst at the same time engaging in three conditions involving cognitive activity (spatial, verbal and mixed spatial-verbal probelem solving) and a control condition. The nature of the concurrent cognitive activity was found to produce differential effects on left- and righthand performance with spatial-cognitive activity being a more effective disruptor of an ongoing, left-handed manual task at the age of 9 years. Above that age verbal and spatial activity appear to have comparable disruptive effects.

Handedness, Body Orientation, and Performance on a Complex Perceptual-Motor Task

Previous experiments (Grant & Kaestner, 1955; Miles & Lewis, 1956; Provins, 1956) have shown no consistent differences attributable to handedness in performance on perceptual motor tasks. Grant and Kaestner (1955) found interaction between handedness and difficulty of task. The purpose of this experiment was to examine left- and right-handed performance on a complex motor task (Humphries & Shephard, 1955). On the basis of Humphries' model (1958) for predicting performance on the Toronto Complex Coordinator (TCC) for various control-display-subject relations, the predicted performance in each of three subject orientations was examined using left and right handed Ss. METHOD The task was 'out of phase' (CD-3) on the Toronto Complex Coordinator (Shephard, 1955). Ss practiced in Positions B-3, B-6, or B-9. The control stick projected toward S and was parallel to the floor. Ss were 15 left-handed and 15 right-handed randomly selected male university students. An S was considered left-handed if he did any two tasks (eating, writing, or throwing a ball) with his left hand (Miles & Lewis, 1956). The experimental design was a 2 X 3 factorial one (two preferred hands, three body orientations) with 6 independent cells, each one consisting of 5 independent observations. Each S was given standard instructions and demonstration and then performed for one period of 5 min. Ss were run randomly as to both position and handedness. Measures were total number of matches, error-match ratio, and error persistencetotal error ratio. These measures are described elsewhere (Shephard, 1955).