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At least 19 recordsLinked to original sources

A large-scale study of handedness and pregnancy/birth risk events: implications for genetic theories of handedness.

Whether left-handedness is due to genetic factors or to pregnancy and birth stress events is an important question for models that attempt to explain the origins and distribution of human handedness. Major genetic theories of handedness, such as those of Annett (1985) and McManus (1981), allow for a nondetermination of some left- or right-handedness by "chance", but they hold that "pathological left-handedness", specifically, is of minimal influence. On the other hand, theorists such as Bakan (1971) and Coren (1995) take the view that right-handedness is a universal human characteristic, presumably due to a polygenic influence, and that left-handedness is essentially always the product of pregnancy and birth risk factors. Research attempting to find associations of left-handedness and unfortunate pregnancy and birthing events has produced very inconsistent results. We report a large-scale study that employed handedness for writing as the criterion for handedness, mothers' reports regarding the occurrence or nonoccurrence of a large number of possible pregnancy and birth stress events, and mothers' reports regarding the handedness of the biological parents and of their offspring. Of the 25 potential stressors studied, only maternal age showed a significant association with left-handedness of offspring. Further, this relationship was quite weak and would account for no more than 1/84th of the approximate 11% incidence of left-hand-edness in the general population. Implications for theories of handedness are discussed.

Adult↗

Maternal age and parity correlates of handedness: gender, but no parental handedness modulation of effects.

Mothers supplied information on the handedness of a total of 1079 children (238 left handed, 841 right handed), and also reported information on the handedness of the biological parents, parental ages when each child was born, parity, and birth complications. A MANOVA, employing offspring handedness and parental handedness (presence versus absence of at least one left handed) as the bases of classification, and parity, maternal age, paternal age, and a birth stress composite score as dependent measures, was applied to the data of female and male offspring separately. For females, there was a significant multivariate effect for handedness, but no effect of parental handedness nor any interaction of the handedness and parental handedness factors. Univariate ANOVAs, following the multivariate analysis, showed significant effects of handedness for the maternal age and parity measures, but not for paternal age or birth stress composite score. The analysis for males showed no significant multivariate or univariate effects. The data suggest, that in the absence of high risk parity and maternal age over 32, only about 7.8% of females are left handed. This implies that as many as 29% or so of female left handers may owe their sinistrality to factors associated with high risk parity and maternal ages over 32.

Adult↗

Handedness conversion in children and parental handedness.

In order to find out which factor, genetic or environmental, is more involved in determining hand usage, the distribution of handedness in Japanese senior high school students and the success of their parents' attempts at conversion of handedness was investigated with respect to four pairings of parental handedness. When a child's handedness was related to that of the parent, children of a left-handed parent were more likely to be non-right-handed than those of both right-handed parents. There was no significant relation between parental handedness and the rate of handedness conversion of children. The results are in favor of the view that human handedness is genetically rather than forcibly determined by parents, although environmental factors such as parents' interference are involved in decreasing the incidence of non-right-handedness in Japan.

Child Rearing↗

On the evolution of handedness: a speculative analysis of Darwin's views and a review of early studies of handedness in "the nearest allies of man".

Scientists today who seek clues into the evolutionary origins of human handedness make extensive use of evidence from comparative studies, that is, studies that ask whether handedness occurs in other species, especially apes and monkeys, as the Darwinian principle of continuity would seem to imply, or whether it is uniquely human. Early investigations had the same goal and drew on much the same kind of evidence. In this article, I review studies of animal handedness in the period before 1859, when Darwin published On the Origin of Species, and afterward, through the 1st decade of the 20th century. Inasmuch as Darwin's published writings contain hardly any statements about handedness and none at all about its evolution and continuity across species, I also speculate about what Darwin himself might have said on the subject. To do this, I draw on his statements on related matters, such as the form and structure of the hand and the transition from a quadrupedal to bipedal stance, on other writers' reports and opinions about handedness with which he was familiar or likely to have been familiar, and finally, on clues from his own and only statement about animal handedness in an unpublished letter. I conclude by asking whether and how early investigators, lacking any statement by Darwin on the evolution of handedness, invoked his theory of evolution and his views on related matters in the interpretation of their findings.

Animals↗

Effects of culture, sex, and age on the distribution of handedness: an evaluation of the sensitivity of three measures of handedness.

The present study examined the effects of culture, age, and sex on three measures of handedness: writing hand, Annett's primary handedness items, and a measure based on hand preference for 11 activities. Using data from a large international study, the relationship between the culture in which participants learned to write (as defined by Hofstede's cultural dimensions) and adult handedness was examined. Participants who learned to write in formal cultures were less likely to be classified as left-handed than those who learned in less formal cultures. Older participants and those who learned to write in formal cultures were more likely to be classified as left-handed by the Annett and 11 item measures than by the writing hand classification. Across measures females were less likely to be classified as left-handed than males. Handedness for writing was found to be more sensitive to cultural influences than the other measures. These results suggest that some measures of handedness may be more sensitive to specific handedness aetiologies than others.

Adolescent↗

Pathological left-handedness. Left-handedness correlatives in adult epileptics.

Factors associated with left-handedness were examined in a large sample of adults who suffered with epileptic seizures (n = 446) in an attempt to delineate the concept of pathological left-handedness. Three main pathological factors were found associated with left-handedness: (i) right-hemiparesis of early onset; (ii) cognitive deficit; (iii) evidence of left-hemisphere disease on clinical examination. Familial sinistrality was also associated with left-handedness, independently of the above-mentioned pathological factors. Results support a clear-cut distinction between normal and pathological left-handedness. This distinction seems presently important for the evaluation of the great number of anomalies proposed to be associated with left-handedness.

Adult↗

Inventory-derived task handedness preferences of nine professions and their associations with self-report global handedness preferences.

The handedness preference (laterality) of 1,196 professionals grouped in nine professions previously reported using self-reported global handedness and scores on a modified Edinburgh Handedness Inventory was further defined by evaluating the association between profession and the 10 manual tasks of the inventory. The previously reported ranking of professions in order of increasing righthandedness of laterality score arose from the handedness of specific inventory tasks. A similar association was found for self-reported global handedness. The evidence continues to support the hypothesis of an association between handedness preference and specific aptitudes or skills in this sample of professional persons.

Aptitude↗

Handedness, cerebral lateralization, and measures of "latent left-handedness".

Two surveys were conducted to investigate the relationship between handedness and various variables that have been considered to be either more fundamental indices of an underlying laterality than handedness or have been proposed as moderating the relationship between handedness and cerebral lateralization. In the first survey (N = 686), sighting eye dominance was found to be related to handedness. In the second (N = 799), arm folding and leg crossing, but not hand clasping or spreading the fingers, were found to be related to handedness. Although these variables are correlated with handedness, they do not have the properties that would make them likely to improve prediction of cerebral lateralization.

Female↗

Pathological left-handedness and ambiguous handedness: a new explanatory model.

A new model is presented which attempts to explain three pathological handedness phenotypes: pathological left-handedness (PLH), pathological right-handedness (PRH) and ambiguous handedness (AH). Revisions in the original model of PLH were prompted in order to account for reports of a raised incidence of both manifest left-handedness and AH in more severely retarded and/or brain-injured populations--namely, autistic. The new model generates specific predictions on the likelihood of different etiological subgroups within these disorders.

Autistic Disorder↗

Two measures of laterality in handedness: the Edinburgh Handedness Inventory and the Purdue Pegboard test of manual dexterity.

This study investigated the relationship between a paper-and-pencil measure of laterality in handedness, the Edinburgh Handedness Inventory, and a test of manual dexterity, the Purdue Pegboard test. Individuals of extreme handedness based on the Edinburgh Handedness Inventory (laterality Quotients of +90 to +100 and -100 and +54; 50 each) were recruited to complete the Purdue Pegboard test of manual dexterity. Subjects in the sinistral group had significantly smaller mean discrepancy scores in performance between their hands [t80 = 5.12, p = .0001] and much greater variance in performance than dextral subjects (F1,98 = 2.85, p = .0001). These findings suggest that paper-and-pencil measures of lateral preference for handedness may not identify proficiency of subgroups within a sinistral group.

Functional Laterality↗

The octave illusion in relation to handedness and familial handedness background.

The octave illusion is produced by a dichotic sequence of tones that alternate in frequency between 400 and 800 Hz, such that when the right ear receives 400 Hz the left ear receives 800 Hz; and vice versa. Most listeners obtain the illusion of a single high tone in one ear alternating with a single low tone in the other ear. Further, most right-handers hear the high tone on the right and low tone on the left. The present study examined localization patterns in this illusion as a function of handedness and also of familial handedness background. The effect of handedness was highly significant: the tendency to hear the high tone on the right and the low tone on the left was lower among mixed handers and left-handers than among right-handers. The effect of familial handedness background was also highly significant: the tendency to hear the high tone on the right and the low tone on the left was lower among those with a sinistral familial background than among those with a purely dextral familial background. These findings are discussed in relation to the hypothesis that perception of the illusion serves as a reflection of the direction of cerebral dominance in most individuals.

Adult↗

Handedness and language among the mentally retarded: implications for the model of pathological left-handedness and gender differences in hemispheric specialization.

The relationship between handedness and language was examined among 238 mentally retarded subjects representing the four DSM III classification ranges of mental retardation. Language ability was found to be significantly related to handedness, with an increased prevalence of left-handedness among those individuals with language deficits. In addition, both expressive and receptive language ability interacted with gender, with the main effects of each language variable being stronger for females than males. Although no main effects were found for severity of retardation, a significant interaction was found between severity and gender. Results support the model of pathological left-handedness and are discussed within the context of this theory, as well as with regard to gender differences in cerebral lateralization of language and cognitive functioning.

Adolescent↗

Birth order and left-handedness revisited: some recent findings in chimpanzees (Pan troglodytes) and their implications for developmental and evolutionary models of human handedness.

This paper examines the relationship between parity, pregnancy outcome, and handedness in a sample of captive chimpanzees (Pan troglodytes). The relation between parity, maternal age and positive or negative pregnancy outcome was assessed from life history data for 536 chimpanzees housed at the Yerkes Regional Primate Research Center. The incidences of negative pregnancy outcome (notably spontaneous abortions and stillbirths) were significantly higher in parities of 8 or higher compared to all other parities. In a sub-sample of 165 chimpanzees, the relation between parity, maternal age and handedness was assessed to determine whether left handedness may serve as a marker of prenatal pathology. These analyses indicated that left-handedness was more prevalent in 1st and 8 or higher parities compared to parities between 2 and 7, respectively. Possible prenatal hormonal and periparturitional factors are discussed as possible mechanisms for the observed findings.

Animals↗

Hemispheric asymmetries of visual evoked potentials in relation to spatial frequency, handedness and familial left-handedness.

The effects of handedness and of familial left-handedness on the asymmetry of the cerebral hemispheres were investigated by means of visual evoked potentials. Square gratings of different spatial frequencies were presented, at 1 Hz in ON-OFF mode to 60 subjects: 30 right-handers and 30 left-handers, 15 with familial handedness and 15 without in each group. The results show that the patterns of hemispheric asymmetry differ in right- and left-handers. They also show that in left-handers these patterns depend on the presence or absence of familial left-handedness, whereas in right-handers the role of this genetic factor is less evident.

Adolescent↗

Handedness in children at school entry: does the 'Mesker test' provide a valid method for testing writing handedness?

The 'Mesker test', an experiment devised after the psycho-motor dominance test described by the Dutch paediatrician Mesker, was evaluated as a method for testing writing handedness in 145 children at school entry in Crewe Health Authority. Also included in the assessment was if, and how these children know their laterality. Positive outcome was measured as Mesker test result corresponding to spontaneous hand-preference in symbol copying. The correct indication of right arm or leg was evaluated in relation to the outcome by chance. The Mesker test could not confirm hand-preference in children at school entry. There was no significant relation to the child's maturity and no significant consistency in test performance. The sub-group of right-handed writers who confirmed their handedness showed an almost significant level of consistency. No more children who thought they knew the right side indicated the correct limb then could have been arrived at by chance. This was not significantly related to having been taught, writing handedness or maturity. It is concluded therefore, that at school entry age children don't have a good knowledge of their body's laterality. Although the Mesker test does not confirm writing handedness at school entry, it may be useful in older children with inconsistent laterality.

Child, Preschool↗

Handedness as a continuous variable with dextral shift: sex, generation, and family handedness in subgroups of left- and right-handers.

Percentages of left-handed relatives were compared between subgroups of left-handers and of right-handers to test the prediction that the subgroups are ordered for probability of carrying the rs +/gene (hypothesized by the right-shift theory of handedness). Data included families of undergraduates and Open University students who described their children as well as other relatives. Linear relationships were found between subgroup order and percentage of left-handed relatives. In agreement with previous evidence that some right-writers with weak sinistral preferences (class 2) are in fact more dextral than consistent right-handers (class 1), class 2 tended to have fewer left-handed relatives than class 1 in both samples. Left writers with weak dextral tendencies (class 7) tended to have more left-handed relatives that consistent left-handers (class 8). Comparisons of the distribution of subgroup handedness in undergraduates and their parents revealed strong effects for sex and for generation. In both cases, the main contrasts were not between left-handers and right-handers but between left-handers plus right-handers with weak dextrality and right-handers with strong dextrality. The findings are consistent with the theory that the relevant factor is not handedness as such but, rather, the absence or presence of the rs +/gene.

Adolescent↗

Left handedness and handedness switch amongst the Chinese.

The incidence of left handedness amongst the Chinese, as in the case of people with more traditional cultures, is reported to be low. However, there is a group of native left handers, often unrecognized as such, who use the right hand for writing and drawing but the left hand for most other tasks. They had experienced pressure during childhood to shift their preferred hand from left to right. This paper compares the handedness profile, eyedness, footedness, and finger tapping performance of right handed, left handed, and handedness switch Chinese subjects.

Adult↗

Handedness of handedness researchers.

This study tested the hypothesis that laterality and handedness researchers are more likely than other researchers to be left-handed. A questionnaire assessing hand preference was sent to authors of articles which either dealt with handedness (N = 50) or other aspects of laterality (N = 100) or did not concern laterality (N = 50). The proportion of left-handers was highest in the handedness group (12.9%) and lowest in the non-laterality group (5.0%), but this difference did not reach significance.

Awareness↗