Left-handed Persons Research Articles

DO LEFT-HANDED COMPETITORS HAVE AN INNATE SUPERIORITY IN SPORTS?

This study assessed handedness distributions among (a) sporting competitors (n = 1,112) and nonsporting university students (n = 1,112), (b) sporting competitors engaging in interactive (n = 576) and in noninteractive sports (n = 536), and (c) sporting competitors engaging in direct interactive (n = 219) and indirect interactive (n = 357) sports. Chi-squared showed that there were statistically significant differences in proportions of left-handed persons in (a) sporting competitors and nonsporting university students, (b) sporting competitors engaging in interactive and noninteractive sports, (c) sporting competitors engaging in interactive sports and nonsporting university students, and (d) sporting competitors engaging in direct interactive and indirect interactive sports. It appears that left-handers are more common among those who engage in competitive manual activities. This superiority of the left-handers may be fully explained by a consideration of tactical or strategic factors associated with handedness during sporting interactions. The results with important implications for the measurement and evaluation of handedness are discussed in the light of the current findings on laterality.

Improvement of Functional Magnetic Resonance Imaging by a Novel Fibre-Optic Device and 3D Software

This report describes three years of clinical experience with a new set of devices aimed at improving functional MRI of speech areas. They provide a valuable tool for pre-operative definition of hemispheric localization and spatial extension of these areas, especially in left-handed persons. The fibre-optic device described here transmits stimuli for cognitive tasks to patients undergoing MR investigations. Cognitive tasks elicit a defined brain activity lasting for several minutes. The resultant metabolic changes are detectable by functional MRI. The software (FIT ware) applied to process raw data allows semi-automated segmentation of the brain so as to obtain 3D images. Furthermore it allows the superposition of functional data. The effectiveness of the equipment was assessed on the basis of data from 140 fMRI studies. Intra-operative verification in eight patients with tumours located in the speech areas showed that the new set-up identified the speech-dominant side in each case and located speech areas in accordance with electrophysiological procedures.

Inheritance of randomness

The mouse mutant iv is characterized by ‘a random determination of a developmental process‘ in that 50 rather than 100% of the homozygotes have situs inversus. The same explanation is given to the inheritance of situs inversus in the human immotile-cilia syndrome. There are probably two alleles of the responsible gene, one for control of the proper asymmetry and one without control and hence resulting in equal numbers of situs solitus and situs inversus in the homozygote. Left-handedness may be similarly inherited; furthermore, because of its high prevalence (around 10–12%) it has been assumed that there is an advantage of carrying both alleles (‘balanced polymorphism’). With these two assumptions, a prevalence of left-handedness of 12.5% is expected, a 50% chance of left-handedness in matings between two left-handed persons, and equal numbers of discordant and left-handed concordant monozygotic twins. These values are close to those actually found. As the values for (female) homosexuality are similar to those of left-handedness a similar inheritance is proposed.

Asymmetries of manual motor response in relation to age, sex, handedness, and occupational activities.

Questions about left- and right-hand asymmetries require the analysis of preference and manual skill with respect to handedness. Hand preference and hand skill were examined in relation to sex, age, and occupational activities. 512 adults from manual, mixed, and intellectual activities and 253 children were tested for their manual preferences and performance. Analysis of variance followed by Scheffé post hoc tests, for right-handed adults, indicated significant effects for occupational activity and sex in dexterity and strength. Manual workers, under technological pressure, seemed more consistent in their manual preferences than their peers. For left-handed persons there were no significant effects. Dexterity and strength were also related to sex and age, suggesting different cultural opportunities for both sexes in relation to motor activities.

Left-handedness and mortality.

We examined mortality associated with handedness in two ways. A simulation using national data suggests that lower mean age at death among left-handed persons, previously offered as evidence of higher mortality, can be explained exclusively by the age distribution of laterality. Second, empiric evidence from a 6-year cohort study of 3774 older adults from East Boston, Massachusetts, demonstrates that left-handedness is not associated with mortality (relative odds = 1.04, 95% confidence interval = 0.79, 1.36).

Cephalic muscle tenderness and pressure pain threshold in a general population

Tenderness and pain thresholds in pericranial muscles were studied in a general population. A random sample of 1000 adults aged 25–64 years was drawn as part of the Glostrup Population Studies, and 740 adults were examined. This study was part of a multifacetted, epidemiological study of different headache disorders according to the new headache classification. Manual palpation and pressure pain threshold with an electronic pressure algometer were performed by observers blinded to other information such as the person's history of headache, previous illness and mental state. The muscles most commonly tender to manual palpation were the lateral pterygoid (55%), the trapezius (52%), and the sternocleido-mastoid muscles (51%). Females were more tender than men in all the muscles examined by manual palpation. In total, the young age group was more tender than the old age group ( P = 0.03). Pressure pain thresholds on temporal muscles showed lower thresholds in women than in men ( P < 10 −3), and in the total population thresholds increased with age ( P < 0.05). No side-to-side difference in tenderness by manual palpation was found, while the right side showed increased pain thresholds in right-handed individuals ( P < 10 −4). No side-to-side difference was found in left-handed persons. This study provides data about the normal population and forms the neccesary basis for evaluating the importance of muscle tenderness in headache subjects and other selected groups.

Grip strength and hand dominance: challenging the 10% rule.

The purpose of this study was to test the utility of the 10% rule in hand rehabilitation. The 10% rule states that the dominant hand possesses a 10% greater grip strength than the nondominant hand. This rule has been used for many years to assist therapists in setting strength goals for patients with injured hands. The sample for this study consisted of 310 male and female students, faculty, and staff from a small, private liberal arts college located in Pennsylvania. Grip strength was measured with a factory-calibrated Jamar dynamometer. Results showed an overall 10.74% grip strength difference between dominant and nondominant hands. This finding verified the 10% rule. However, when the data were separated into left-handed and right-handed subjects, a 12.72% difference for right-handed subjects and a -0.08% difference for left-handed subjects was found. In conclusion, this study showed that the 10% rule is valid for right-handed persons only; for left-handed persons, grip strength should be considered equivalent in both hands.

Left-handedness and field-independence

Left-handed persons have been reported to show less field-independence than right-handed persons. Using a large sample of left-handers (96), a replication attempt was made and the opposite result was obtained. Left-handers were found to be more field-independent than right-handers. Results from previous studies were probably due to the use of extremely small samples of left-handers (four and 10). Different instrumentation was ruled out since the Embedded Figures Test and the Group Embedded Figures Test are essentially the same.

Alcohol use among right- and left-handed persons in a small community.

SUMMARY. Left-handed men under age 40 were heavier consumers of alcohol than right- handed men (ronsignificant difference). Differences by handedness are not as great in women; however, a greater proportion of right-handed women abstain. Several studies suggest a relationship between handedness and drug use. Harburg et al. (1) noted that there is a greater tendency toward smoking among left-handers and that left-handed smokers tend to smoke more than right-handed smokers. Bakan (2) reported a high proportion of left- handers among 47 men alcoholics in a general hospital alcoholism ward. Both studies suggest that further inquiry into the differences between left- and right-handers in the use of such substances as alcohol, tobacco and coffee might yield significant results. Recent large-scale studies of alcohol consumption (3-5) have not considered handedness differences. The present study compares the alcohol consumption of a sample of right- and left-handers in Teeumseh, Michigan, considering differences in age and weight between the two groups. Men and women are analyzed separately. METHOD

Perception of Musical Stimuli by the Dichotic Listening Test Comparative Study between Japanese and French

Musicians and nonmusicians were tested in the recognitions of four kinds of dichotically presented music stimuli : recorded tones, chords, rhythms and melodies. Nonmusicians were 18 subjects (A), who worked in fireman's agency in Paris, France, whose ages ranged from 18 to 28 years (average : 20.2 years) and whose years of musical experiences ranged from 0 to 5. Musicians were 8 students in musical college (Conservatoire national supérieur de Musique de Paris): 5 right-handed (B) and 3 left-handed persons (C), whose ages ranged from 18 to 25 years (average : 21.8 years), whose years of musical experiences ranged from 10 to 18 (average: 12.8 years). 1) In the tone test, the mean score for right and left ears were nearly the same for both A and B. 2) The chord test revealed a significant left ear superiority for A, and the tendency of the higher score in left ear was seen for B. 3) In the rhythm test, the score for the right ear had a tendency to be higher than the one for the left ear, both in A and B. 4) In the melody test, the score showed a tendency of left ear superiority for A, but the tendency of right ear superiority was seen for B. Bever and Chiarello (1974) found a right ear reference in the detection of musical stimuli when they used musicians as subjects. Johnson made the dichotic listening task involving violin for musicians and nonmusicians. The musicians demonstrated a right ear superiority, while the nonmusicians performed better with the left ear. He interpreted that musicians mainly used the left hemisphere to process musical stimuli, while nonmusicians used the right hemisphere. The results of Bever and Chiarello, and Johnson nearly agree with the results of our musical dichotic listening test for nonmusicians and musicians in France as well as the results of our former studies for pupils of chorus club in elementary school, stdents of philharmonic club in senior high school and students in musical college in Japan.

Handedness and Temperament

Answers to a questionnaire from members of the Tecumseh Community Health Study showed a relationship of handedness and temperament, especially for younger persons. Left-handed persons rated themselves more emotional than right-handed persons, and younger sinistral males appear less extraverted than dextrals.

Handedness and smoking.

This article reports the observation that proportionately more left-handed persons smoke than dextrals, and a greater proportion of left-handers than right-handers smoke 10 or more cigarettes daily, regardless of sex, race, stress of residence (or social class), and prior history of smoking. This association is especially strong among males and persons residing in residence areas of high stress (low income, low education), and weak among black females and persons who smoke 30 or more cigarettes daily. The sample was drawn from four census areas in Detroit differing by race, socioeconomic levels, and crime rates. Respondents and their spouses were 25 to 60 yr. old, married, and had relatives in the metropolitan area (N = 1496).

Cerebral laterality and verbal processes.

Research suggests that we process information by way of two distinct and functionallly separate coding systems. The localization of these two processing systems appears to be somewhat dependent on cerebral laterality, which has been shown to vary in right-handed and left-handed persons. To test the dual coding model, right-handed and left-handed subjects learned lists of abstract and concrete words under various conditions of visual and tactile interference. Right-handed subjects showed a significant superiority in the remembering of highly concrete items, while total recall did not differ reliably between groups.

Functional asymmetry in the face.

The possible existence of one-sided dominance in the face, similar to the phenomena of handedness and footedness, has been investigated by studying smiling pattern, movements of the angles of mouth, winking, platysma contraction, raising and everting the upper lip with dilatation of the nostril, and vertical wrinkling of the forehead, on 300 right-handed and 30 left-handed persons. The conclusions are as follows: 1. The large majority of persons investigated do not use the two sides of face equally. 2. Facial ambilaterality is a rare feature. 3. There is no clear-cut correlation between handedness and the dominant side of the face. 4. The greater percentage (58.66%) of right-handed persons show a left-sided smile and find it more convenient to perform almost all exercises with the left side of the face. A still greater percentage (73.33%) of left-handed persons shows a right-sided smile and a better performance of all exercises with the right side of the face. The contralateral relationship of handedness to the dominant side of the face is significant in the right-handed and more so, in the left-handed persons.

Strength of Left-Handedness and Facial Recognition Ability

Facial recognition ability was tested in groups of left-handed and right-handed subjects; strength of handedness was assessed by a hand-usage questionnaire and by dexterity testing. Weakly left-handed persons scored significantly lower in facial recognition ability than all others. The results support the general hypothesis that decreased cerebral lateralization of function is associated with slight impairment of non-verbal, visual-spatial skills of the minor hemisphere.

The objectivation of verbal discrimination ability further investigation

The aim of this investigation was to observe basic variables which might be of significance for objective speech audiometry. Contrary to our former experiments, the near-threshold stimulation with indicative test words leads to contingent negative variation (CNVs) which are equal to or even smaller than the CNVs after supra-threshold stimulation. Thus the CNV can be used for objective testing of verbal discriminatory ability only as a qualitative, but not as a quantitative parameter.Independent of whether the presentation was monaural or binaural, the distribution of CNV and the complementary waves were symmetrical over the two hemispheres. Selective concentration of attention on one ear produced particularly strong but symmetrical CNV. No evidence was found for a hemispheric predominance in either right-handed or left-handed persons; but it is still possible that predominance might occur in pathological conditions.The CNV may be used very well as a qualitative test, e.g. in examining cases of aphasia, bu...

A Case of “Pure Alexia”

(1972). A Case of “Pure Alexia”. International Journal of Mental Health: Vol. 1, Current Trends in Western European Neuropsychology, pp. 8-11.

Left-Handedness

The left-handed child or adult lives in a right-handed world. The entire structure of our society assumes right-handedness and by assumption we punish. When a left-handed person writes, his very posture looks awkward and oftentimes will make a watcher uncomfortable. The writing product of a left-handed person is sometimes totally illegible to the right-handed person. One wonders what would occur if we had two distinct methods for teaching writing—a technique for the right-handed and a technique for the left-handed. The following is a technique for the left-handed.—C.C.E.

Recognition and recall of dichotically presented verbal stimuli by right- and left-handed persons

Twelve left-handed and twelve right-handed subjects performed dichotic listening tasks using three different types of verbal materials as stimuli; meaningful words, function words, and nonsense words. Of the three types of verbal stimuli, the function words were most successfully repeated following dichotic presentation, and the nonsense words were least successfully repeated. When the mean scores at the left ear were compared with those at the right ear, higher mean scores were consistently obtained at the right ear by both of the handedness groups on all three types of verbal stimuli. Furthermore, it was found that the absolute difference scores between the two ears for the left-handed subjects tended to be smaller than those for the right-handed subjects. These latter results may be interpreted as supporting the theory of greater hemispheric equi-potentiality for left-handed subjects than for right-handed subjects.

Reliability of Profile and Front-Facing Directions in Children's Drawings

The reliability and various hypotheses associated with facing direction of drawn figures were investigated utilizing 1305 children in grades 4, 5, and 6 in a large public school system. Front-view drawings were highly reliable. Right-profile drawings were highly unreliable and left-profile drawings were reliable for boys but not for girls. Machover's contention that girls draw more front views than boys was supported. Boys drew more right-facing profiles than girls but left-facing profiles revealed no sex differences. The frequency of profile drawings did not change with grade level, which seems to indicate that profile drawings were not related to maturity, at least for the age range used in this study. The drawing of profiles facing right or left could not be accounted for by handedness alone. Other variables seemed to be operating. Several hypotheses have arisen concerning the interpretation of the direction in which a drawn figure is facing. Machover (2, p. 93) felt that the drawing of profiles is related to evasiveness. She contended that profiles appear more frequently in the drawings of boys than girls and concluded that females are less evasive than males. She implied that females are, therefore, more sociable than males. Another hypothesis presented by Machover (2, p. 93) was that profiles are seldom found in the drawings of very young children and, when they appear, indicate maturity. A third hypothesis suggests that right or left profile facing is related to handedness. Machover (2, p. 94) pointed out that right-handed persons, when drawing profiles, tend to draw them facing the left side of the page while left-handed persons tend to draw profiles facing right. This study was an attempt to measure the reliability of profile and frontfacing drawings by normal children and also to gather data which would shed some light upon the above hypotheses.