Left-hand Superiority Research Articles

A left-hand superiority for the implicit detection of a rule

We set out to test the hypothesis of right-hemisphere superiority for the implicit detection of a rule. Forty healthy men provided speeded manual responses to randomly presented digits from 1 to 6 (left hand to 1–3, right hand to 4–6). Red digits on trial n signaled that the response on trial n+1 should be made with one hand, blue digits with the other hand. White digits gave no signal (control trials). Half the participants were told that the stimulus color conveyed a rule that could be exploited to improve performance, the other half were not. After completing the first run, participants' awareness of the presence and nature of the rule was assessed and all were debriefed. Participants then performed a second run with identical stimulus conditions. In Run 1, none of the participants reported being aware of the nature of the rule. Reaction times (RTs) were longer after signal than no-signal trials, but only for the left hand. Participants informed about the presence of a rule tended to have longer RTs, irrespective of hand. In Run 2, RTs were shorter after signal than no-signal trials, and there were no differences between hands. The observed RT effect for the left-hand points to a right-hemisphere superiority for the detection and application of a rule in the absence of verbal awareness. Longer (instead of shorter) RTs in the signal trials are discussed in the framework of interhemispheric inhibition.

Motor Preparation of Manual Aiming at a Visual Target Manipulated in Size, Luminance Contrast, and Location

We conducted two experiments to investigate whether the motor preparation of manual aiming to a visual target is affected by either the physical characteristics (size or luminance contrast) or spatial characteristics (location) of the target. Reaction time (RT) of both finger lifting (ie stimulus-detection time) and manual aiming (ie movement-triggering time) to the onset of the target was measured. The difference of RT (DRT) between two tasks (ie the difference of task complexity) was examined to clarify the temporal characteristics of manual aiming per se during visuomotor integration. Results show classical characteristics: RT decreased as either the target size or luminance contrast increased. Furthermore, the task-complexity and target-location factors significantly interacted with each other, where the aiming RT was longer than the finger-lifting RT and the effects of target location on RT differed for each task. However, the task factor did not interact with either the size or luminance-contrast factor, implying that the motor preparation of manual aiming is associated with the spatial characteristics rather than the physical characteristics of the target. Inspection of DRT revealed that the time needed for motor preparation for an ipsilateral target was significantly shorter than that for a contralateral target. This was the case both for the left and for the right hand. Foveal targets required longer processing time, implying a disadvantageous function of motor preparation for the gazed target. The left-hand superiority for the target appearing in the left visual field was also observed. Such lateralised effect and left-hand advantage to the left visual field in manual aiming suggest that visuospatial information processing is activated during the preparation of aiming action, with faster processing in the right hemisphere.

Concurrent Counting and Typing: Lateralized Interference Depends on a Difference Between the Hands in Motor Skill

In previous demonstrations of differences between left- and right-handers in dual-task performance, participants' hand preference has been confounded with asymmetry of manual skill. The present study was designed to disentangle those two factors as sources of lateralized interference in the concurrent-task paradigm. Forty-eight normal adults (24 females and 24 males) counted backward by ones or by twos while typing an easy or difficult sequence of letters with either hand. When participants were grouped according to self-reported hand preference, both groups showed bilaterally symmetric slowing, relative to single-task conditions. However, when the same participants were grouped according to manual asymmetry in the baseline condition, the cognitive task interfered significantly more with the faster hand than with the slower hand. Baseline typing rate, averaged across hands, did not influence dual-task interference. Both self-reported left-hand preference and left-hand superiority in baseline typing were associated with reduced interference on the cognitive task, and the reduced interference in those groups seemed to reflect relatively loose coupling between manual and cognitive tasks. The results support and extend Caroselli et al.'s (1997) findings regarding the effect of baseline manual asymmetry on the pattern of dual-task interference. Irrespective of the participant's hand preference, the presence or absence of baseline asymmetry may be sufficient to determine whether dual-task interference is lateralized.

Tactile line-bisection in normal subjects.

The effects of spatial position, handedness, and hand of performance were assessed in 36 normal subjects using a tactile line-bisection task described in 1980 by Bowers and Heilman. An interaction between hand of performance and spatial position indicated that both hemispace and anatomical pathways determine laterality effects. Neither the left-hand superiority nor the leftward error in the midline condition by both hands found in an earlier study could be observed here. Only right-handers were influenced by starting condition, which in this setting acted as a spatial cue. Finally, some subjects used nonspatial strategies, a confounding factor that needs evaluation in further studies.

Sensory and motor aspects of pseudoneglect, hemifield, and hemispace in the tactile modality

Two experiments were conducted with right-handed adult subjects to investigate motor and sensory components of a tactual line bisection task performed under three conditions: at midline, in the left, and in the right hemispaces. In the sensory experiment we found a left-hand rather than a right-hand superiority under the midline condition and, in the motor experiment, a right-hand rather than a left-hand superiority. The results were discussed with respect to hemispheric specialization and hemispace theories. Furthermore, we found a pseudoneglect (subjects bisected to the left of the midpoint) in the sensory experiment and a surprising reversed pseudoneglect (subjects bisected to the right of the midpoint) in the motor experiment.

Hemispheric Specialization in Visual, Tactile and Crossmodal Assembling Tasks

There is ample evidence that the right or non-language related hemisphere of the brain is superior in processing of spatial information. This issue appears less clear when a task involves elaborate mental operations that require the integration of spatial information at a stage beyond mere perceptual discrimination. Examples are block design tasks, which are frequently used as estimates of general intelligence. Results of these tests have been contradictory as to whether there is a right hemispheric advantage for their execution. This study was aimed to look at a possible hemispheric preponderance in block design tasks comparing visual, tactile and crossmodal spatial performance. A two-dimensional template had to be reproduced by arranging cubes with surfaces different in both colour and texture. In the visual condition the template was given in the visual modality and the cube arrangement was under visual control. In the tactile condition the template was presented tactually and the cube assembly had to be done under entirely tactual control. In the crossmodal condition the template was presented visually and the assembly was restricted to tactual control. Task completion time (TCT) and number of correct responses (NCR) were compared between right hand and left hand responses. Only in the crossmodal condition a constant left hand superiority of performance was found. Non-crossmodal tasks did not show a constant hemispheric preponderance. In the tactile condition allowing for easy differentiation of input to one or the other hemisphere TCTs varied only according to the compatibility of side of afferent input and side of assembling action irrespective of the hemisphere engaged.It is concluded that mental operations requiring spatial assembling not necessarily engage the non-dominant hemisphere to a larger extent than the language .

Influence of cognitive style and interstimulus interval on the hemispheric processing of tactile stimuli.

16 adult subjects performed a tactile recognition task. According to our 1984 study, half of the subjects were classified as having a left hemispheric preference for the processing of visual stimuli, while the other half were classified as having a right hemispheric preference for the processing of visual stimuli. The present task was conducted according to the S1-S2 matching paradigm. The standard stimulus was a readily recognizable object and was presented tactually to either the left or right hand of each subject. The comparison stimulus was an object-picture and was presented visually by slide in a tachistoscope. The interstimulus interval was .05 sec. or 2.5 sec. Analysis indicated that the left-preference group showed right-hand superiority, and the right-preference group showed left-hand superiority. The notion of individual hemisphericity was supported in tactile processing.

Learning effects of piano playing on tactile recognition of sequential stimuli

To examine the effect of learning experiences of piano playing on a tactile sequential recognition task, two experiments were conducted. In the first experiment, pianists and control subjects were given sequential tactile stimuli and were asked to report the simulated fingers and the order. The pianists showed a left hand superiority and performed better than the control group. In the second experiment, the skilled pianists and the control subjects were given both sequential tactile stimuli and auditory stimuli (unrelated melodies) simultaneously. The sequential stimuli recognition of the skilled pianists was interfered with by the presentation of the unrelated melody, and this tendency was more prominent in their left hand, while the performance of the control subjects was not affected by the presentation of the melody. These results suggest that pianists employed a special strategy, such as transforming tactile stimuli into something like a melody to improve their performance. Based upon these results, effects of learning experiences on hemisphere function were discussed.

Tactile spatial ability: Lateralized performance of deaf and hearing age groups

Hearing adults, 8- and 6-year-old children, together with deaf 9-year-old children, were tested on a unimodal haptic matching task. One additional group of adults was tested with a shorter stimulus presentation time. Data indicated that left-hand superiority was most evident in the performances of the older hearing children, and of the adults with the shorter presentation time. Hemispheric specialization was less noticeable for the younger hearing group, but the task may have been too difficult. A slight right-hand superiority was found in the performance of adults with long presentation time. This may reflect the simplicity of the task for these subjects. Deaf children did not show any clear hand differences, but were superior in overall performance to hearing children.

Braille reading and left and right hemispace

Twelve blind adults were timed in locating phonologically and semantically defined targets in Braille lists. The “reading” hand was placed either out from or across the body, i.e. in ipsilateral or contralateral hemispace. Despite strong and consistent, if idiosyncratic, hand superiorities for all types of list, contrary to two previous reports there was no evidence of either a general left-hand preference or an overall left-hand superiority. Moreover neither the magnitude nor the direction of hand superiorities changed when hands were tested in contralateral hemispace. At least in this complex continuous task, hemisphere-hand connections appear more important than hemisphere-hemispace relationships. Left-hand (or left-hemispace) superiorities in tactual tasks of a verbal nature may only occur with novel, unfamiliar or perceptually degraded materials.

左利きおよび右利き成人の触認知機能における大脳半球機能差

A tactile recognition test was conducted to examine the laterality differences in the adult left and right handers. In one condition (Non-rotation condition), tactually presented nonsense figures were matched to the visually presented recognition display. In another condition (Rotation condition), tactual stimuli were presented in various direction so that subjects matched the stimuli to the visual display by means of mental rotation. The results obtained from the right handers showed that there was no hand difference in the Non-rotation condition while significant left hand superiority was revealed in the Rotation condition. Left handers did not show any hand difference in both conditions. These results suggest that hemisphere difference in tactile recognition of the left handers is not identical to that of the right handers.

Evidence for a Right Hemisphere Superiority and for a Serial Search Strategy in a Dot Detection Task

In Experiment I the subjects manually signaled whether a solid dot was present or not in an array of empty dots presented either in the right or in the left visual field. The dots were either three or six and the target could appear in any of the possible locations. The results showed (a) a left visual field superiority; (b) a left hand superiority; (c) faster responses to three-dot than to six-dot displays, and (d) an effect of the location of the target in the display. Experiment II exactly replicated the previous experiment with the exception that the stimuli were centrally projected. The results showed: (a) a left hand superiority; (b) an effect of the number of dots in the display. These results can be interpreted to indicate: (a) a right hemisphere specialization in a simple feature detection task without any spatial component; (b) the compatibility of a right-hemisphere advantage with a serial search strategy.

Perception of numerical stimuli felt by fingers of the left and right hands.

Three experiments are reported in which blindfolded right-handed adults felt numerical stimuli with the middle fingers of their left or right hands. These stimuli consisted of collections of raised dots in random arrangement to be enumerated (Experiment I), collections of evenly spaced raised dots in a straight line to be enumerated (Experiment II), and raised digits to be identified (Experiment III). Differences between hands were only found in Experiment I. The left hand was faster, apparently reflecting specialisation of the right cerebral hemisphere for the analysis of complex spatial stimuli. A fourth experiment, in which collections of raised dots in random arrangement to be enumerated were felt through a piece of cloth by subjects who were not blindfolded, confirmed the left hand superiority and demonstrated that it had not arisen from loss of sight of the movements of the dominant hand.

Differential Finger Movements and Hand Preference

In an attempt to replicate a study by Kimura and Vanderwolf (1970), normal left-handed and right-handed subjects were asked to flex a single finger or pairs of fingers at the middle joint. Both hands were found to be equally proficient at this task and no differences between right- and left-handers were found. When left-handers were divided into inverters and non-inverters according to hand-writing posture, a left hand superiority was a found for the right-handed and the left-inverted subjects, while the left-non-inverters showed a right hand superiority. Paired finger flexion was found to be more useful in discriminating between the handedness groups. These findings support the idea that the neural mechanism for hand preference is not based on an asymmetry in the control of fine movement. They also support the theory that two separate groups of left-handers exist, and the they can be differentiated by their handwriting postures.

Handedness and hemispheric asymmetry in the control of movements.

This study investigated the influence of hemispheric specialization of function on the motor performance of the hands. Right-handed (n=7), ambidextral (n=21), and ambisinistral (n=12) subjects performed Fitts' (1954) reciprocal tapping task under two conditions with each hand. Conditions had the same index of difficulty but differed in movement precision. The left hand of right-handers was superior in the condition requiring the greatest amount of preprogramming. Conversely, the right hand was not superior in the condition having the greatest demand for feedback control. For ambidextrals, left-hand superiority in the relatively preprogrammed condition was also revealed. Ambisinistrals showed no significant difference between conditions with either hand. The results partially support the hypothesis that the motor performance of the hands mirrors the dominant processing mode of their contralateral hemisphere. Failure to find supportive evidence in ambisinistrals is consistent with the contention that they lack hemispheric specialization of 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.

Dichhaptic hand-order effects with verbal and nonverbal tactile stimulation

The palms of normal right-handed subjects were stimulated dichhaptically, i.e., with competing, bimanually presented tactile stimuli consisting of pairs of letters, pairs of digits, or pairs of line orientations. The subjects were required to identify both stimuli in a particular order, and order of report was compared between hands and across stimulus materials. Results indicated right-hand superiority for letters and left-hand superiority for lines; no hand differences occurred for digits. However, observed differences between hands appeared with second reports only, suggesting that measures of tactile storage are more sensitive to laterality differences than measures closer in time to actual stimulation.

Lateral differences in tactile directional perception

Between-hands differences in the tactile perception of direction were assessed in normal righthanded subjects by a unimodal tactile matching task. The left hand superiority found in earlier studies employing a crossmodal tactile-visual matching procedure was again shown in this investigation. Thus the indications of hemispheric asymmetry in the mediation of tactile-spatial performances coming from studies which have utilized tactile-visual matching tasks cannot be ascribed to the crossmodal component in these tasks. The problem posed by the occurrence of “exceptional cases” in investigations of hemispheric asymmetry of perceptual function is raised.

利手の實驗的研究

1. Problem of Handedness: Men are mostly right-handed, and left-handedness is exceptional, and as such it becomes a problem of interest and scientific research. But no definite theory of its origin and real nature has been established. The question of handedness has to be considered from two different angles. They are unilateral preference and unilateral superiority. Though they are inseparably united in the actual cases, one refers to native tendency of using one hand in preference to the other, if it is native at all; and the other to the combined results of such tendency and post-natal practice.This study aims to approach this question of handedness through the survey of the actual difference in the capacities of the two hands. And this question can be treated under three main headings.(1) The actual. facts of bilateral difference and the frequency and degree of handedness.(2) The causes of handedness.(3) Physical and mental characteristics of the left-handed.2. Experiment: We chose five different kinds of tests-(1) grip, (2) tapping for 30 seconds, (3) peg-board for 1 minute, (4) tracing a star drawn with double lines (3 mm apart) with pencil, and (5) cutting with scissorsand administered to the entire group of children of one primary school, 801 in all, of whom 416 were boys and 391 were girls.3. Results and Conclusions: This report includes only the first three tests mentioned above, The percentage of the capacities of the left hand to the right hand (i.e. L/R×100) was calculated and we called this an index of left-handedness.(1) The average of motor capacities of each school year for boys and girls are given in Tables 1, 2 and 3.(2) According to the average of. the capacities of both hands the relative efficiency of the left to the right is as follows. Grip Tapping Peg Board Boys 96.58% 86.50% 91.54% Girls 93.71% 87.17% 90.87%(3) The percentage of children who show the left-hand superiority is as follows. Index of Grip Tapping Peg Board Left-handedness No. % No.% No.% above 101 Boys 1 19 31.32 29 7.60 70 18.92 above 101 Girls 92 25.20 21 5.74 56 15.56(4) The number of individuals who show left-band superiority in one, two, or three kinds of tests is 43.31 for boys and 38.25 for girls.(5) The number of children reported as left-banded by teachers in charge is 30 (7.2 %) for boys and 20 (5.1%) for girls.(6) There is no difference of the total capacity of both hands between the right-handed and the heft-handed children.(7) For one hand only the order of efficiency is as follows-1st right hand of the right-handed, 2nd left hand of the left-handed, 3rd right hand of the left-handed, and 4th left hand of the right-handed.(8) The difference of the two hands is most marked in the speed of movement and not so marked in the strength.(9) The difference of the two hands is greater with girls than with boys(10) This research indicates that the frequency and degree of handedness do not regularly increase or decrease with the age-level.