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Relation of handedness with season of birth of professional baseball players revisited.

We reexamined the relationship between month and season of birth and handedness in male professional baseball players listed in Lahman's Baseball Archive Vol. 4.5 database. The sample of 8,016 individuals (left-handed = 1,658; right-handed = 6,358) played major league baseball between 1900-2001. A slightly higher, but statistically significant, percentage of left-handed players were born in June compared to other months, and in the winter-spring months, but we were unable to corroborate Rogerson's spring and early summer categorization of handedness as related to birth season. The data did not support the hypothesis that the prevalence of left-handedness is related to season of birth.

Baseball↗

Hemispheric differentiation and dream recall: subjective estimates of sleep and dreams in different handedness groups.

Previous investigations pointed to a relationship between hemispheric asymmetry and dream recall. Since handedness may reflect the extent to which cerebral organization is lateralized, it was hypothesized that differences in dream recall might exist between different handedness groups. A selected sample of 78 college students (38 right-handers, 25 left-handers, 15 mixed-handers) completed a seven-day sleep and dream diary upon final awakening, at home. Results showed that significantly more dreams are recalled by females compared to males and by right-handers compared to mixed-handers and left-handers. The latter finding is tentatively interpreted as due to a more direct access to aspects of oneiric material structured in the left hemisphere by right-handers, whose language centers are located in the same hemisphere. Unexplained findings of the only other investigation concerning handedness and sleep variables (Hicks, Pellegrini & Hawkins, 1979), which showed greater variability of sleep duration in mixed-handers, were not confirmed by the present study.

Dominance, Cerebral↗

The left brain determines the degree of left-handedness.

The contribution of right- and left-hand skills to left-handedness was studied in 42 left-handed male subjects. Hand preference was assessed by the Edinburgh Handedness Inventory. Hand skill was assessed by a peg-moving task; 10 trials were given to each hand. Peg-moving times decreased linearly with each trial (visuomotor learning). Both hands exhibited equal learning capacities. The learning curves were the same for the left-hands of left-handers with and without familial sinistrality (FS). The right-hand of left-handers with FS was found to be slower than that without FS. The right- and left-hand skills and their learning curves were about the same in left-handers with right-hand writing, exhibiting no difference from the left-hand skill and learning curve of left-handers with left-hand writing. Right-hand skill decreased linearly as left-hand preference increased from -40 to -100; left-hand skill was not related to hand preference. Right-minus left (R-L) time for peg moving increased linearly with hand preference from -40 to -100. R-L time for peg moving linearly decreased as the right-hand skill increased; the left-hand skill was not associated with R-L time for peg moving. It was concluded that the right hand (left brain) determines left-handedness; the neural structures only on the left side exhibit pronounced plastic changes to genetic and environmental influences in left-handers.

Adult↗

Does physical activity behavior vary by handedness?

PURPOSE: Explore whether adults'physical activity behavior or their use of physical activity behavior-change strategies, as derived from the Transtheoretical Model, differed by handedness. METHODS: A cross-sectional survey of 151 adults' hand preference (i.e., handedness: right, left, ambidextrous) and their use of the behavioral and cognitive processes of change, decisional balance scores (i.e., pros minus cons), self-efficacy, and their stage of change for physical activity involvement. RESULTS: Left-handers showed significantly less use of the behavioral and cognitive processes of change compared to right-handers (M = 46.9 vs. M = 40.5 and M = 46.9 vs. M = 40.5, respectively). Left-handers were also significantly more likely to be in the earlier (i.e., inactive or irregularly active) stages of change relative to right-handers (84.6% vs. 48.1%, respectively). DISCUSSION: Handedness may be a previously unrecognized, heritable correlate of physical activity behavior and the use of physical activity behavior-change strategies.

Adolescent↗

[Latent handedness and individual hemisphericity].

An attempt was made to see the relationship of latent handedness (Luria, 1966) with individual hemisphericity, which was evaluated by a version of Hemisphericity Test (HT) devised by Ogura & Hatta (1983) and Cognitive Mode Questionnaire (CMQ; Sakano & Ohgishi, 1983). Subjects were 125 undergraduates (69 males and 56 females). In males, one of those three criteria for latent handedness, i.e. arm-folding subtest, showed a connection with HT; right-arm-uppermost subjects (R group) preferred verbal to nonverbal stimuli more often than left-arm-uppermost subjects (L group). These results support Sakano's hypothesis that the arm-folding subtest reflects individual hemisphericity (Sakano, 1982). Also, HT scores differed significantly between those two groups classified by CMQ. This result indicates the connection between CMQ and individual hemisphericity, whereas those subtests for latent handedness did not show any relation with CMQ. In females, no significant relation could be found among those three tests. Possibly these sex differences are related with those sex differences responsible for the degree of cerebral asymmetry.

Adolescent↗

[Does left-handedness affect the pattern of cerebral blood flow during cognitive activity?].

In most people the left hemisphere of the brain is dominant for language functions. Because of an increased incidence of atypical language lateralisation in the right hemisphere of left-handed neurological patients, more systematic studies on handedness and cerebral asymmetry of language have been undertaken. The present study is aimed at clarification of the relationship between handedness and language dominance in healthy subjects. Lateralisation was measured directly using functional transcranial Doppler sonography in left-handed subjects. Twenty-six individuals participated in the study. Three kinds of tasks were used, differing in the material involved and in appropriate strategies to be employed by the subjects. Two important parameters of the MCA blood flow were analysed: mean relative increase in the blood flow velocity (MDV) and specific patterns of cognitive task performance (i.e. performance profiles). Our results indicate that the incidence of the right hemisphere dominance for language depends on the degree of handedness, since only in the group of consistent left-handers language was right lateralised. In other left-handers both cerebral hemispheres were functionally equivalent. The measurement of MCA blood flow velocity changes using transcranial Doppler ultrasonography seems to be a simple and non-invasive method of assessing the functioning of the two hemispheres of human brain.

Adult↗

Independent dimensions of hand preference: reliability of the factor structure and the handedness inventory.

Healey, Liederman, and Geschwind (1986) suggested that handedness is not a unidimensional trait. They devised a questionnaire with 55 handedness items and 6 familial hand preference items and administered it to 290 adults. Their analysis identified four independent factors underlying hand preference. In the current study, the reliability of all but one of the items on the original inventory was established by retesting 83 of the original subjects. An additional analysis revealed that approximately 2% of the population could be considered to have "ambiguous" handedness in the sense that they indicated unstable hand preference according to the criteria suggested by Soper and Satz (1984). The reliability of the factor structure was evaluated by factor analyzing data from a new sample of 487 subjects, demographically similar to those in the original sample. All four factors reappeared with minor shifts in item loadings. The original and second samples were then combined, and four factors were again found, even when the sample was reconstructed so that there were equal numbers of males and females. On the basis of these new analyses our initial conclusion was confirmed: hand preference must be characterized along more than one dimension.

Journal Article↗

Handedness and the bilateral asymmetry of the jugular foramen.

This paper examines the proposed association of bilateral asymmetry of the jugular foramen as an indicator of handedness observable from cranial morphology. The jugular foramina of 54 subjects were observed for size asymmetry during routine autopsy procedures. Hand preference data were collected on each subject from family members. Of the 54 subjects, 47 were documented as being right-handed and 7 as being left-handed. These values approximate the average percentage of right-handed versus left-handed individuals from larger populations. Jugular foramen asymmetry was qualitatively identified for 36 subjects (66.7%) and was judged equivocal for the other 18 (33.3%). Of the 36 subjects exhibiting asymmetry, 28 (77.7%) showed positive correlation between the asymmetry direction and handedness. This moderate level of congruence, coupled with the result that 4 of the 7 left-handers exhibited dominant right-side foramina, casts doubt on the reliable use of jugular foramen asymmetry for estimating handedness.

Adolescent↗

[Analysis of investigative data for hand-clasping, arm-folding and handedness in Han, Hui and Mongolian ethnic groups].

In this paper, authors re-calculated the data of ZHENG Lian-bin et al. in 1996 (Hand-clasping, Arm-folding and Handedness) by log-linear model. The results demonstrated both agreement and disagreement with the published data. The results show as follows: (1) There are no relations between hand-clasping and populations, sex; (2) There are obvious correlation between arm-folding and sex, but no relation between arm-folding and populations; (3) There are three factorial effects among handedness, populations and sex; (4) In our study, we found association between handedness and hand-clasping, arm-folding and non-association between hand-clasping and arm-folding.

English Abstract↗

Prevalence of the three categories of handedness among Malawian school children.

A cross sectional study of prevalence of left, right and mixed handedness was made on 512 Malawian school children (240 boys and 272 girls) aged 6-17 years. Handedness was assessed using questionnaire incorporating questions on hand preferred for eight unimanual activities. Interviews with guardians, pupils and teachers were conducted to assess the pressure experienced by children to use right hand for unimanual activities. The overall prevalence of left-, right- and mixed-handers was 3.9%, 90.4% and 5.7%, respectively. Association between handedness and age or gender of children was nonsignificant. 96.2% of guardians and 92.7% of teachers were insistent upon use of right hand for unimanual tasks. Most of non-right handed children indicated that they had experienced pressure to use right hand for unimanual activities but they were still using left hand for one or more manual tasks. 28 pupils indicated that they stopped using left hand under the pressure from guardians and teachers.

Adolescent↗

Handedness and the laterality of breast cancer in women.

In a pilot study of 138 women with mastectomies that explored the consistent finding of more left breast cancer in American women, associations were found among handedness, initial breast cancer laterality, and age. To test these findings further, 889 subjects were added to the original sample. The resulting sample of 1,027 consisted of 861 right-handed, 94 ambihanded, and 72 left-handed subjects aged 21 to 84. A chi-square test showed a statistically significant association between ipsilateral breast cancer before age 45 and contralateral breast cancer after age 44 in right-handers, chi 2 (1, n = 861) = 4.169, p less than .05. The association was also significant for left-handers, chi 2 (1, n = 72) = 4.036, p less than .05. In addition, a chi-square test showed a statistically significant association between handedness and earlier development of breast cancer, chi 2 (1, n = 933) = 13.9, p less than .01. Almost twice as high a percentage of left-handers as right-handers developed breast cancer before age 45. Log-linear analysis demonstrated no significant associations of nodes with either handedness or age. Overall, there was no statistically significant association between the laterality of breast cancer and a history of breast cancer in a primary relative, chi 2 (1, n = 1,024) = 1.38, p greater than .05. In some presently unknown way, lateral asymmetries of neurotransmitters may contribute to an explanation of the findings.

Adult↗

Handedness distribution in a residential population with severe or profound mental retardation.

Handedness within a sample of mentally retarded subjects was assessed using a procedure that includes a large number of items appropriate for lower functioning subjects, with multiple presentations within and between sessions one week apart. Results revealed a dramatic shift from the normal right-handed bias primarily due to the presence of a large mixed-handedness subtype, which proved to be ambiguously handed in that these subjects showed inconsistent hand preference within items. Reasons why this subtype has not been reported previously were discussed, and a model was postulated to explain the resultant handedness distribution in terms of probable central nervous system substrate.

Adult↗

Bilateral asymmetry of long arm bones and jugular foramen: implications for handedness.

The analysis of asymmetry of the arm long bones and of the cranial jugular foramen has been used to suggest handedness in humans. However, because of the unavailability of documented skeletal material, neither criterion has been systematically tested. If both criteria are associated with handedness, they should also be intercorrelated within individuals. Data were collected from skeletal material of 125 males and 57 females to test whether this intercorrelation exists. According to Chi-square analysis, no statistically significant association was identified. After examining several hypotheses, it was concluded that until further substantiation, neither criterion is related to handedness to a degree appropriate for forensic science identification from skeletal remains.

Adult↗

Handedness, language dominance and aphasia: a genetic model.

A simple two-allele Mendelian model of the genetics of handedness is described and fitted to data in the literature. The model proposes that there are two alleles, D (dextral) and C (chance), the homozygous DD genotype producing only right-handers (directional asymmetry), the homozygous CC genotype producing a racemic mixture of 50% right-handers and 50% left-handers (fluctuating asymmetry), and the heterozygote, DC, being intermediate between the homozygotes and producing 25% left-handers, and 75% right-handers. It is also suggested that the true population incidence of left-handedness is 7.75%, deviations from this figure being due to either criterion shifts or selection biases. The same model is then fitted, by means of a number of minor conceptual extensions, to data from the literature on the relationship of handedness to language dominance, acute and permanent aphasia, and visual processing dominance.

Aphasia↗

Handedness in musicians.

In order to study the prevalence of left- or mixed-handedness in musicians, we decided to examine a population of professional musicians. We assessed the handedness pattern of 382 members of 7 orchestras. The prevalence of non-right-handedness in musicians was found to be much the same as in the general population. Similar results emerged from a study of young music school pupils. We conclude that brain structural tomographic imaging should ideally be performed, and the pattern of cerebral asymmetry analysed in order to assess cerebral lateralization in musicians.

Brain↗

Handedness in first-episode psychotic patients and their first-degree biological relatives.

We evaluated the handedness of 58 schizophrenia patients and 54 of their relatives, 23 patients with major depression with psychosis and 24 of their relatives, 36 patients with bipolar psychosis and 33 of their relatives, and 119 nonpsychiatric subjects and 42 of their relatives. Computerized tomography measures were also available for a subset of the psychotic patients. The schizophrenia patients were significantly more left-handed than any of the other groups, and increased sinistrality was also associated with larger lateral ventricle to brain area ratios. The relatives of the schizophrenia patients did not significantly differ on handedness from either the relatives of the affective psychosis patients or the nonpsychiatric subjects. Our findings do not support the notion that left-handedness in schizophrenia is genetically influenced. More research with larger family member data sets is warranted to further explore this possibility.

Adolescent↗

Regional distribution of cerebral arteriovenous malformations. Interactions with sex and handedness.

On the basis of clinical observation and a developmental theory of cerebral laterality, Geschwind and Galaburda suggested that cerebral arteriovenous malformations (AVMs) are more common in the left hemispheres of male patients. We tested this hypothesis by examining interactions among sex, handedness, and location of lateralized, supratentorial AVMs. Data from 112 cases were analyzed by log-linear procedures. We found that (1) females had a greater proportion of left-hemisphere AVMs, whereas males showed an opposite trend; (2) there were no interactions between sex and handedness; and (3) nondextrals showed a higher proportion of AVMs located in frontal regions, regardless of the hemispheric side of the lesion. Although these findings appear to be inconsistent with the Geschwind-Galaburda hypothesis, the inconsistency may be attributable to the embryonic stage at which this developmental abnormality occurs. In addition, the unexpected findings may also reflect our use of multivariate statistical procedures, which control for interaction effects.

Adolescent↗

The asymmetrical genetic determination of laterality: flatfish, frogs and human handedness.

The determination of the left-right body axis is unlike that of the two other axes because left-right positional information is not required to specify mirror-image structures on the two sides. When the left and right sides of the body are not mirror symmetrical such positional information is required, as is a mechanism for reading that information. There are several possible gradient schemes for left-right information, including symmetrical gradients from which the information is extracted by spatial differentiation. The genetic mechanisms for the control of handedness are not known. There is no evidence for 'left-handed' and 'right-handed' genes, only for mutations that can interfere with handedness in a non-specific manner. Such mutations never produce situs inversus with a frequency greater than 50%. The situs of individual organs shows a strong correlation, suggesting a global mechanism such as a gradient of left-right positional information. Many asymmetries in vertebrates follow a pattern in which growth on the left is favoured over growth on the right. This may be related to the 'dexiothetism' of chordate ancestors postulated by Jefferies.

Animals↗