Left-hand Advantage Research Articles

Left-hand advantage in right-handers for spatial constant error: Preliminary evidence in a unimanual ballistic aimed movement

While the superiority of the right hemisphere for the processing of spatial relationships in normal right-handers has been largely accepted, it is surprising that evidence for an advantage of the left “nondominant” hand over the right “dominant” hand in spatial motor tasks is up to now almost totally lacking. We report preliminary evidence that normal right-handers perform open-loop ballistic aimed movements with a smaller constant error when using the left rather than the right hand. In addition, constant error is found to be minimal for movements directed toward the left half-field.

Dichhaptic laterality and field dependence

Relationships among laterality, field dependence, and sex were investigated using right handed subjects. Dichhaptic measures of laterality showed a significant left-hand advantage for the discrimination of irregular shapes. No significant relationships were found between laterality and sex or sex role perceptions nor between laterality and field dependence. A modality of response effect on the laterality task was interpreted in terms of the functional cerebral space principle.

Effect of Processing Mode on the Degree of Motor asymmetry in the Manual Stroop Test

In a reaction-time study using conflicting Stroop colour-word stimuli and unimanual-choice responses, Schmit and Davis (1974) have provided data incidentally showing a right-hand advantage for the verbal processing of the material, contrasting with a left-hand advantage for the chromatic processing of the same material. The present experiment successfully replicated the interaction effect, using a within-subject design and a simplified procedure. This effect indicates the preferential involvement of the left hemisphere in the verbal processing of the Stroop material. More interestingly, it shows that it may be efficient to use the very simple laterality factors of the output sphere — such as the hand used to make the response — for the study of hemispheric lateralization of cognitive function.

Problem-Solving Strategies and Manifest Brain asymmetry

The dichhaptic stimulation procedures developed by Witelson (1974) for the study of brain lateralization in children were modified and extended for use with adults. Consistent with findings in children, an overall left hand advantage was found under conditions of simultaneous or dichhaptic stimulation, although it was not found under conditions of monohaptic stimulation. The major purpose of the study was to determine whether in adults hand differences (assumed to reflect hemisphere utilization) could be influenced by the use of differential problem-solving strategies. Half the Ss were instructed to approach the haptic learning and recognition problems in a "sequential" or "analytic" manner, and half to approach them in a "holistic" or "Gestalt" manner. The results indicated that the degree of left hand superiority was indeed influenced by this manipulation, although it is to be noted that the actual basis of the effect is unclear. The results were consistent with the idea that brain lateralization must be defined, not strictly by tasks, but by strategies used by subjects to perform the tasks used to detect and study that lateralization. It is suggested that this immensely complicates the issue of interpreting the origin and basis of individual and group differences in laterality effects.

Handedness Effects in Kinesthetic Spatial Location Judgements

This experiment examines hemispheric assymetry in reproduction of spatial location in the kinesthetic modality. Using a dichotomous presentation technique, blindfolded, right-handed subjects moved both arms (arm positioning task) or the thumb (thumb positioning task) of each hand simultaneously to predetermined spatial locations and were subsequently asked to reproduce these locations. The results showed a marked left hand advantage only in the thumb positioning task suggesting that the right hemisphere was superior in performing this task. These data were discussed as they relate to other evidence pertaining to cerebral hemispheric specialization in motor activities.

Superiority of the Minor Hemisphere in Commissurotomized Man for the Perception of Part-Whole Relations

The capacity of the right and left cerebral hemispheres to do part-whole matching was independently examined in patients who had undergone cerebral commissurotomy. The ability of each hemisphere to choose from among three sizes of complete circle the one corresponding to a given arc was tested with three different procedures. These involved presentation of the sample arcs and array of circles respectively by a) unilateral touch and free vision; b) free vision and unilateral touch; and c) successive unilateral touch. Two control tests were also run in which the subjects matched circles to circles and arcs to arcs, using the same procedures as in the experimental task. Results show that in all three forms of the test the patients were significantly more accurate when using their left hand to match arcs to the appropriate size of circle, than when using their right, the right hands' scores generally not rising above the chance level. By contrast, on the two control tasks, where like stimuli were matched, both hands did equally well. Since these commissurotomized patients showed no ability to cross match the test stimuli between their right and left hands, the left hand advantage demonstrated in the experimental task apparently reflects a superiority on the part of the right hemisphere in generating a concept of the whole stimulus from partial information.