Distribution Of Hand Preference Research Articles

A Study on Functional Cerebral Lateralization and the Distribution of Hand Preference among Gazi University Students

A Study on Functional Cerebral Lateralization and the Distribution of Hand Preference among Gazi University Students

Hand preference depends on posture in common marmosets

Postural conditions are known to affect hand use in many primate species. It remains to be examined how posture and task differences modulate, or interact with, hand use in common marmosets (Callithrix jacchus). Three experimental conditions were introduced to assess the occurrence of preferential hand use as a function of posture and size of aperture for the subjects to grasp and retrieve the food item bi- or unimanually: ground level condition for requiring quadrupedal posture with enough space for food reaching with both hands, large hole (4cm in diameter) condition for requiring upright posture with available space for both hands, and small hole (2cm in diameter) condition for requiring upright posture with available space for only one hand. While the distribution of hand preference did not significantly differ among the three conditions at the group level, eight out of twelve marmosets did not change hands when identical upright postures were required in large and small hole conditions. Some marmosets simultaneously used both hands when both hands were free to reach the food items; however, the number of left hand users increased when the marmosets were forced to use either hand to pass through the reduced hole size. Significant correlations in hand use between the upright posture conditions were observed, whereas no correlation was observed between the different posture conditions. These results suggest that, although preferential hand use was not found at group level, posture, but not size of aperture, has effects on hand use in individual common marmosets

The distribution of hand preference is discrete: A taxometric examination

The dominant genetic models of human handedness (Annett, 1985; McManus, 1985a) have contrasting views on its nature. Whereas Annett's model proposes that handedness is distributed continuously (following the distribution of performance asymmetries of the hands), McManus's model proposes that handedness is distributed dichotomously. The aim of this study was to investigate the nature of the underlying distribution. The taxonomy of hand preference was analysed by two independent taxometric procedures, 'mean-above-mean-below-a-cut' and 'maximum-eigenvalue', separately in two geographically, demographically, and culturally distinct samples; one of Australian adults (N=787), and the other of Serbian high school students (N=1,224). The analyses revealed a latent categorical structure in both samples, with estimated mean base-rates of a right-handed taxon of 0.80 and 0.94 from the two analyses of the adult sample and of 0.79 and 0.93 from the two analyses of the high school sample. Subsequent analyses showed that the initial right-handed class could be subdivided into consistent and inconsistent right-handed subclasses in both samples. A supplementary analysis, including a measure of hand proficiency in a subset of the sample of Australian adults (N=596), also revealed a latent categorical structure, showing evidence for a categorical latent structure from a continuous measure of hand performance. We conclude that the distribution of hand preferences in humans is discrete and not continuous.

Dynamics of Manual Skill: A Computerized Analysis of Single PEG Movements and Stochastic Resonance Hypothesis of Cerebral Laterality

Hand skill was analyzed using a computerized peg moving task. The durations of single hand movements (PMTs) were accurately measured in right-hand (RH) and left-hand (LH) writers. One trial consisted of 10 movements of the right hand and 10 movements of the left hand. Each participant performed five trials. Women showed significantly higher percentage than men in right-handedness; men showed higher percentage than women in left-handedness. This sex difference completely disappeared after taking the same height range in participants. The mean RH- and LH-PMTs decreased in 5 successive trials, even within a single trial during 10 successive hand movements, indicating a learning effect of repeated hand movements. The LH- minus RH-PMTs exhibited fluctuations within a single trial between positive (faster right hand) and negative (faster left hand) values. LH–RH PMTs were significantly greater than zero, in favor of right hand, in RH-writers, but not significantly different from zero in LH-writers, exhibiting a true fluctuating asymmetry. Participants with no familial sinistrality (FS-) were preponderantly right-handed (ca. 90%), those with left-handed mother and right-handed father (FS+1) showed stochastic distribution of hand preference (50:50). Participants with right-handed mother and left-hander father (FS+2) were not different from FS- individuals. LH–RH PMT was significantly greater than zero in FS- participants, almost equal to zero in FS+1 participants, and greater than zero in FS+2 participants exhibiting greater asymmetry than that in FS- participants. These results suggest a genetic inheritance of direction and degree of handedness, being a a X-linked trait originating from mother's genotype. It was suggested that fluctuating asymmetries may reflect interactions between stochastic resonance phenomena within right and left brains. This property of brain may genetically transmitted from mother's X chromosome; a net effect of stochastic interactions between hemispheres may result in right- or left-handedness, a predominantly unidirectional coupling creating right-handedness, in favor of left brain, and a stochastic bi-directional coupling between hemispheres would be a main trait of left-handers. This new “stochastic resonance hypothesis of cerebral laterality” concerns with stochastic fluctuations in hand-skill asymmetry and inter-hemispheric coupling through corpus callosum, and seems to be important for new developments in handedness research.

HAND PREFERENCE IN TURKISH POPULATION

The distribution of hand preference (self report) was studied in siblings and their parents originating from all parts of Turkey (N = 22,461). In total sample and siblings, there were significantly more right-handed women than men, and significantly more left-handed men than womenno significant sex difference for parents' handedness. The relative number for the right-handed parents significantly exceeded that for the right-handed siblings; the relative number for the left-handed siblings significantly exceeded that for the left-handed parents. It was concluded that there may be a sex difference in hand preference, but being only about 1% more left-handed men, and only about 1% more right-handed women; the right-handedness in new generation (siblings) is less than that in old generation (parents), due to freeing from cultural pressures against the left-hand use in everyday activities.

DIFFERENTIAL CONTRIBUTIONS OF RIGHT AND LEFT BRAINS TO PAW SKILL IN RIGHT- AND LEFT-PAWED FEMALE RATS

Paw preference and paw frequency was studied in female rats. Paw preference was assessed using a modified version of food reaching task in quadrupedal position. Of 68 rats, 56 (82.4%) were right-handed, 7 (10.3%) were left-handed, and 5 (7.4%) were mixed-handed. There were significantly more right-handers than left-handers. The distribution of right minus left (L) paw reach (R + L = 50) was not U-shaped, it was J-shaped like in humans. Estrus cycle was a significant factor influencing the right-paw entry scores: most of left-handers were in estrus and proestrus, most of left­-handers were in estrus, and most of mixed-handers were in postestrus. In right- and non-right-­handers, the frequency of right-paw usage (right-hand skill) increased linearly with testing days, but the frequency of left-hand usage (left-hand skill) did not show significant changes with the successive testing days. Controlling for body weight and estrus only accentuated these results. It was concluded that distribution of hand preference in rats is J-shaped and there is a right-sided population bias in handedness in rats like in humans. The results suggested that motor learning in paw skill is mainly involved the left brain in right- and mixed-handed rats, not the right brain: only the left brain has the inbuilt capacity for motor learning in female rats. Such an asymmetric cognitive control in an animal model may have a major impact in many aspects of biology in respect to normal functioning, superior talents, and disease (see Geschwind, 1985).­

The Relationship Between Handedness and Fine Motor Performance

The aim of this study was to re-investigate the relationship between handedness and asymmetry in hand performance, and the sex difference in motor asymmetry. Three-hundred and ten medical students volunteered as subjects. Handedness was assessed by a 13-item questionnaire adapted from Chapman and Chapman. Fine motor performance was measured using a finger tapping task. In this task, subjects were required to tap as rapidly as possible with their index finger on a mouse button for a period of 10 s. There was a significant correlation between handedness scores and the scores of the finger tapping task. In the total sample, the correlation between hand speed and the handedness score indicated that the distribution of hand preference is associated with left hand speed, but not right hand speed. Results confirmed that right-handed females tend to have more asymmetric motor function than right-handed males.

Left-Handedness and Longevity in Primates

In the present research we used the rhesus macaque to model the decline in the incidence of left-handedness that has been noted in the aged human population. We found a significant group-level bias towards use of the left hand among young-adult macaques, and a significant group-level bias towards use of the right hand among aged macaques. The distribution of hand preference across age classes cannot be explained through simple elimination of left-handed subjects in the aged population. Rather, our data are consistent with a maturational view positing increased use of the right hand with increased age. Similar findings across phylogenetically diverse primate taxa suggest that this phenomenon is an evolutionarily ancient trait. Greater use of the left hand in male versus female macaques indicates that sex differences in hand preference are also deeply rooted in our primate origins.

The distribution of hand preference in normal men and women.

The distributions of the hand preferences (Geschwind scores) were studied in men and women. The incidences of the right-, mixed-, and left-handers were 66.1, 30.5, and 3.4%, respectively. The left- and right-handers (LHs, RHs) were represented by two bars located at the opposite ends of a J-shaped histogram for the total sample, men, and women. The distributions for the total RHs, and male RHs were not J-shaped, but negatively skewed, the mode being close to the mean. The frequencies for the females increased linearly. The distributions for the LHs did not significantly deviate from normality. Except for the LHs, the percentage distributions of the Geschwind scores were J-shaped. The LHs were evenly distributed by chance to be expected in a random sample from a rectangular population. The incidence of weak right-handedness was significantly higher in men than women. The total RHs were more lateralized than the total LHs who showed a tendency toward weak left-handedness. In males, the incidence for weak left-handedness was significantly higher than that for strong left-handedness. The opposite was established for females. The probability of the consistent right-handedness was significantly higher in women than men. The LHs were less lateralized, and more widely dispersed than the RHs. The statistical analysis of the distributions indicated that females tended to be more lateralized, i.e., more right-handed, and more left-handed, than males.

Right- and left-hand skill I: Effects of age, sex and hand preference showing superior skill in left-handers.

Hand preference and hand skill were examined in relation to sex and age from 3 1/2 to 50+ years. The data were drawn from several samples which avoided volunteer bias, either by selecting children according to birth-date or by taking complete class groups. The distribution of hand preference and of asymmetry of skill gave no evidence of systematic changes with age. Younger children were more variable and showed larger absolute differences in favour of the right hand than older children but L-R times were similar over most of the age range. Time for peg moving decreased with increasing age to a minimum in the late teens, remained stable for the next three decades and increased slightly in the 50+ age group. Males were faster than females with the left hand in almost all age groups. Females tended to be faster than males with the right hand up to 10 years of age but males then equalled and surpassed females, to be faster in most older groups. Correlations between hands did not vary systematically with age or sex. Left-handers were faster than right-handers and right mixed-handers were intermediate for peg-moving time by the non-preferred hand, in both sexes and both sets of samples. Differences for the preferred hand were less clear but still favoured left-handers in several comparisons. The findings raise the possibility that left hemisphere specialization for language is achieved through a right hemisphere handicap and that left-handers escape this risk to cerebral efficiency.

Hand preference and skill in 115 children of two left-handed parents.

A second sample of children of L × L parents resembled a first sample (Annett, 1974) in the distribution of hand preferences and of hand skill. The mean difference between the hands in skill (L—R) was slightly but not significantly biased in favour of the right hand and 31 per cent were sinistral writers. Three tests were made on the combined samples of the hypotheses, derived from the right shift (RS) theory of handedness (Annett, 1972), that the L — R skills of the majority are not biased to either side, but that some are biased to the right hand like controls, in spite of being reared by two left‐handed parents. Children with a possibly pathologically sinistral parent, and children in families where neither left‐handed parent had a close sinistral relative, resembled controls more closely than the remaining children. The L — R distribution was compatible with expectations for three genotypes, as expected if the RS depends on a single gene (Annett, 19786).Analyses for sex differences found sons and daughters alike for hand, eye and foot preferences and for L—R skill. Analyses of reports of developmental problems of speech, reading, writing or spelling found an excess of affected males over females smaller than expected in the general population. The incidences of such reports in the sons and daughters of L × L families were almost identical, with incidences reported for the fathers and mothers, respectively, of dyslexics (Annett & Kilshaw, 19826). The findings were consistent with the view that sex differences in hand preferences, L — R skill and the risk of developmental language problems in the general population are all due to the more effective expression of the rs + gene in females than males, and that the gene is more often absent in the children of L × L families than in the general population.

Head Orientation Position during Birth and in Infant Neonatal Period, and Hand Preference at Nineteen Weeks

This study of lateral preferences of normal full-term infants found, as predicted, that infants who were delivered from a left occiput anterior or transverse birth position (head turned to the right) exhibited a neonatal right supine head orientation and a right-hand preference in visually guided reaching tasks at 19 weeks. Contrary to prediction, infants delivered from a right occiput anterior or transverse birth position (head turned to the left) did not exhibit a left-sided preference in either neonatal head position or hand preference. Results are discussed in relation to other research which found a right shift in neonates' head orientations and in the distribution of hand preference in the human population. The findings suggest further investigation into the relationship between prenatal and postnatal postural asymmetries and the continuing development of laterality.

Distribution of hand preferences in monkeys

The hand preferences of 58 monkeys ( Macaca mulatta) on two tactile discrimination tasks are analysed in the light of the binomial model proposed by Annett [1].