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PubMed1990

Early age at menopause among left-handed women.

Associations have been suggested between handedness, autoimmune disorders, and reproductive hormonal changes. The purpose of this study was to test a proposed relationship between handedness and age at menopause. Two national survey data sets were used to compare recalled ages at menopause. Mexican-American women, ages 35-74, naturally postmenopausal for at least 1 year, were selected from the Hispanic Health and Nutrition Examination Survey (HHANES). White and black women were selected from the National Health and Nutrition Examination Survey (NHANES-I) using similar criteria. The mean age at menopause was found to be earlier among left-handed women than right-handed women from the NHANES-I data set. In the HHANES data set, the mean age at menopause was significantly earlier among left-handed women than in right-handed women (t = 2.35, P less than .05). Early age at menopause among left-handed women may result from misclassification of handedness among older women or differential mortality among left-handed individuals. Alternatively, the association may be related to possible correlations between left-handedness and autoimmune disorders, which may include reactions against hormone receptor sites and oocytes.

Adult↗
PubMed1977

Motoric laterality imbalance in schizophrenia. A possible concomitant of left hemisphere dysfunction.

Two hundred schizophrenics were compared to 200 normal controls on a measure of laterality that included handedness, footedness, and eye dominance scales. Schizophrenics showed more left-sidedness on the laterality score. The established relationship between motoric and cognitive aspects of functional brain asymmetry, found in neurological and normal populations, suggests that the leftward tendency of schizophrenics may be manifested in cognitive and conative functions as well. These results seem to corroborate previous findings indicating that schizophrenia might be related to left hemisphere dysfunction. No relationship was found between handedness and eye dominance either in the schizophrenic or the normal groups. This finding questions the assumption that eyedness-handedness nonconcordance is a pathological sign.

Adolescent↗
PubMed2002

Patterns of lateralized hand use in an arboreal primate, Simias concolor.

Studies of hand use in nonhuman primates suggest that several species exhibit hand preferences for a variety of tasks. The majority of studies, however, focus on the lateralized hand use of captive nonhuman primate populations. Although captive settings offer a more controlled environment for assessing hand preferences, studies of wild populations provide important insights into how handedness is affected by natural environmental conditions and thus potential insights into the evolution of handedness. To investigate handedness in a population of wild nonhuman primates, we studied patterns of lateralized hand use during feeding in four simakobu monkeys (Simias concolor), an arboreal species inhabiting the Mentawai Islands, Indonesia. Our data show that individual variation in hand preferences for feeding existed among our study animals. In addition, each simakobu expressed a significant hand preference for supporting itself on a branch during feeding, an uncoordinated bimanual task. This bias was most prevalent when the branch used for support was a main branch rather than a terminal branch. When both hands were employed in a coordinated bimanual feeding activity (bimanual manipulation), only two subjects showed a significant bias for feeding. Our data suggest that these individuals are more likely to express significant hand preferences when feeding from stable, rather than precarious, positions within the canopy.

Animals↗
PubMed2006

Lateral preferences in children with intellectual deficiency of idiopathic origin.

The goal of this study was to evaluate lateral preferences in a population of children with intellectual deficiency of idiopathic origin, compared with those of typically developing (TD) children. Two groups of children with mild or moderate intellectual deficiency were observed. Handedness (using a 10-item test and Bishop's card-reaching task), eyedness and footedness were studied. The younger group consisted of sixteen 10- to 11-year olds; the older group comprised fourteen 12- to 14-year olds. A control group of fifteen TD children was matched for age with the younger group of intellectually deficient (ID) children. The results show that the occurrence of left-handedness is not higher in children with ID of unknown origin than in age-matched TD children. However, we observed a marginally reduced tendency toward right-handedness in ID than in TD children: more mixed-handers among ID than TD children; test-retest consistency of hand preference significantly lower in the 10- to 11-year-old ID children than in the age-matched TD children; greater tendency of ID children to use their nonpreferred left hand when the card was presented to the left, as compared with TD children. Left-eyedness and crossed hand-eye preference were also more frequent in ID than in age-matched TD children. No age-related difference in laterality was found in ID children. These results partially support other studies indicating that less rightward asymmetry is associated with intellectual deficiency in children.

Adolescent↗
PubMed1981

Right-hand preference facilitated by rightward turning biases during infancy.

A rightward turning bias is the earliest human asymmetry and may be a precursor of handedness. Head-turning affects arm position as part of the Asymmetric Tonic Neck Reflex (ATNR). The hypothesis was tested that turning biases operate in coordination with the ATNR to promote handedness by measuring reflex behavior during turns in the preferred vs nonpreferred direction. Twenty infants were filmed during spontaneous movement and during the following factorial design: head turned left vs right; voluntarily vs passively; 30 degrees vs 70 degrees. The incidence, strength, and duration of the ATNR were least when the child turned toward his/her preferred side. When right-preference children turned rightward, the occurrence of the ATNR was no better than chance. Thus, a child can orient toward the right hand with minimal intrusion of the ATNR upon limb position, perhaps promoting right-handedness.

Elbow Joint↗
PubMed1988

Evidence for a maternal effect on infant hand-use preferences.

Left-handed offspring occur more frequently when one or both parents are left-handed. Among parental pairs with discordant handedness, left-handed mothers have more left-handed offspring than do left-handed fathers. No previous study has looked for this maternal effect in the hand-use preferences of infants. Handedness of 42 infants (21 females) 6-13 months of age (M = 10 months) was assessed by a reliable and valid procedure that provides hand-use preference scores separately for reaching and unimanual manipulation of objects. Equal numbers of age-matched male and female infants were formed into three groups representing different patterns of parental handedness: neither parent left-handed, father left-handed, mother left-handed. Infants of left-handed mothers showed more left hand-use than infants of left-handed fathers or infants of right-handed parents. Indeed, 64% of infants with left-handed mothers had significant left hand-use preference scores whereas none of the infants in the other groups had significant left hand-use preference scores. Possible mechanisms for this maternal effect on infant hand-use preferences are discussed.

Child Development↗
PubMed1994

Evaluating the empirical support for the Geschwind-Behan-Galaburda model of cerebral lateralization.

The Geschwind-Behan-Galaburda (GBG) model of cerebral lateralization provides a complex but testable theory of the origins and associates of cerebral lateralization. An overall evaluation of the model suggest that it is not well supported by empirical evidence and that in the case of several key theoretical areas, the evidence that does exist is inconsistent with the theory. In particular: the concept of "anomalous dominance" is shown to be theoretically and methodologically flawed; a meta-analysis of the relationship between handedness and immune disorders finds a marginal overall association, and while three conditions (allergies, asthma, and ulcerative colitis) do show significant associations with left-handedness, two other conditions (myasthenia gravis and arthritis) show significant negative associations with left-handedness. Finally, a review of the origins of the neural crest, and its associations, suggests there is almost no empirical support for the GBG theoretical model in this area.

Autistic Disorder↗
PubMed1995

Sex and familial sinistrality differences in cognitive abilities.

Cognitive functioning was assessed in 69 left-handed males and females with a positive family history of left-handedness and in 77 left-handed and 55 right-handed males and females without familial left-handedness. Compared to females, males performed better on numerical reasoning and on two visuospatial tasks involving spatial manipulations (Figure Rotation and Surface Development). Within the group of left-handers, the multivariate effect for Familial Sinistrality was significant. Left-handers with familial left-handedness exhibited better scores on numerical reasoning, on verbal reasoning, and on two visuospatial tasks involving visual closure (Hidden Figures, Picture Completion) than did left-handers without left-handed relatives. The nonfamilial left-handers also exhibited lower scores on both inductive reasoning tasks when they were compared to their right-handed counterparts. The outcome runs contrary to the prevalent conclusion that left-handers with left-handed relatives are more likely to exhibit lower performances on visuospatial tasks than left-handers without such relatives.

Adolescent↗
PubMed1996

Hand preference and hand skill in children with autism.

Hand preference and hand skill was assessed in two broad age groups of children with autism, children with learning disabilities, and control schoolchildren. The first group comprised children ages 3-5 years and the second group of children ages 11-13 years. Degree of handedness remained relatively stable across age groups, particularly within the autistic and learning-disabled populations. The main difference was between the subject groups, with the normal controls more lateralized than either the children with autism or children with learning disabilities. As with degree of handedness, consistency of handedness also differed significantly between subject groups with the normal controls more consistent in their hand preference than the other two groups. In addition, younger children were less consistent in their hand preference than older children. However, the present study found no evidence of a dissociation of hand skill and hand preference in children with autism compared to children with learning disabilities and normal developing children.

Adolescent↗
PubMed1988

Brain modulation of the immune system: association between lymphocyte responsiveness and paw preference in mice.

An association between handedness and immune disorders has been described in man, left-handers being more susceptible to autoimmune or allergic diseases. However, this correlation was established between handedness and clinical signs of immune disorders without studying immune functions. Using an animal model, we demonstrated for the first time an association between handedness and lymphocyte reactivity. Left-handed mice were shown to exhibit higher mitogen-induced T lymphocyte proliferation than right-handed animals.

Animals↗
PubMed1982

The origin of left hand preference: pathological and non-pathological influences.

Models of the origin of left hand preference were tested with prospective data. Infants with and without a history of perinatal complications, matched for age, sex and parental handedness, were filmed at 6 weeks of age. Children with a history of perinatal complications lacked the rightward headturning bias of those children without a history of perinatal trauma. Children with a history of perinatal complications were also deviant with reference to the duration of a postural reflex and its degree of lateralization. Perinatal complications may delay the establishment of volitional hand use as well as increase the probability of left-handedness. The data were interpreted as supporting SATZ's (Cortex 8, 121-135, 1972) rather than BAKAN et al.'s (Neuropsychologia 11, 363-366, 1973) model of "pathological" left-handedness.

Birth Injuries↗
PubMed1983

Incidence of left-handed writing in a college population with reference to family patterns of hand preference.

Hand preference data were obtained for 1816 university students, 4793 siblings and 3632 parents. Results support the following conclusions. (1) There is currently a 13.8% incidence of left handedness among young adults, representing a dramatic increase over past generations. (2) Left and right-handed respondents do not differ in terms of familial sinistrality. (3) Mother's left-handedness is associated with an increase in the incidence of sinistrality for sons and daughters, while father's left handedness is related only to sons.

Adult↗
PubMed1987

The dual task paradigm: speech dominance or manual dominance?

Two hundred and sixty monolinguals divided into subgroups based on gender, handedness, and familial left-handedness, were given a concurrent task, verbal-manual interference paradigm. The primary purpose of the study was to test whether the dual task interference effects were more related to hemispheric speech or manual dominance factors. The dominant hand, regardless of handedness, underwent relatively more tapping interference than the nondominant hand. The obtained results seriously question the basic assumptions underlying the interpretation of the dual task paradigm as an assessment index for hemispheric language lateralization. A possible explanation of this result that is in keeping with known hemispheric language representation proportions in left-handers is offered based on left hemisphere ipsilateral control of the left hand.

Female↗
PubMed1988

Comments on Lindesay: laterality shift in homosexual men.

The raised incidences of strong left-handedness and of mixed-handedness in homosexual men, as in dyslexics, are mutually consistent under the normal distribution function, as expected by the right shift theory of handedness. It is argued that atypical laterality in these groups is better described as a "reduction of right shift" than as a "left shift".

Differential Threshold↗
PubMed1996

Laterality and types of dyslexia.

The right shift theory of handedness and cerebral specialization suggests that there is an underlying substrate of random lateral asymmetries in all higher animals and a specific factor in humans which increases the probability of left hemisphere advantage. The specific factor displaces the random distribution along a continuum of asymmetry in favour of the left hemisphere and the right hand. The distribution of handedness in families can be explained if the shift to dextrality depends on a single gene, rs +, when the frequency of the gene is estimated from the proportion of dysphasics with unilateral lesions of the left versus the right hemisphere. The gentoype proportions suggested a genetic balanced polymorphism with heterozygote advantage for laterality and ability. Application of the model to developmental dyslexia led to the hypothesis that both homozygotes (rs -- and rs ++ genotypes) are at risk for reading. The critical question was whether the type of cognitive problem differs as expected, speech based processing for the rs -- and non-speech based for the rs ++. The former should include more left and mixed handers, while the latter should be more strongly dextral than controls. Evidence for this double dissociation between type of cognitive disability and type of handedness has been found in poor readers and in other samples.

Cognition↗
PubMed1995

The effect of lateral asymmetries on breast feeding skills: can midwives' holding interventions overcome unilateral breast feeding problems.

OBJECTIVE: to determine whether the three human lateral asymmetrical behaviours (maternal handedness, maternal preferred cradling side, neonatal preferred head turning) affected the development of a unilateral breast feeding problem (UBP). DESIGN: quasi-experimental comparing 32 postnatal women who reported a UBP with 28 who did not. SETTING: maternity unit in the south of England. PARTICIPANTS: 60 mother/baby pairs where it was the mother's first attempt at breast feeding, there were no structural abnormalities of the breasts or nipples, no obstetric abnormalities, and where the mother had had no more than 100 mg pethidine in labour. The babies had to be less than 72 hours old at recruitment, show no abnormal behaviour, such as floppiness or irritability, and weighed 2500 g or more. MEASUREMENTS AND FINDINGS: handedness test, preferred cradling side established, neonatal preferred head turning established, demographic data. The two groups of women did not differ on demographic characteristics, but multiparous women were less likely to report a UBP or a neonatal preferred feeding side and more likely to be feeding at six weeks post delivery. Neither dominant handedness nor maternal preferred holding side alone were associated with a UBP but when the dominant hand was different from the preferred holding side, the women were more likely to have a problem side and to report a preferred feeding side. A neonatal head turning preference was associated with a UBP but not with success/failure of breast feeding at six weeks post-delivery. There were no associations between the holding interventions used by midwives and the successful continuation of breast feeding until six weeks post-delivery. KEY CONCLUSIONS: there is no conclusive evidence associating the management of a UBP with differing intervention holds. IMPLICATIONS FOR PRACTICE: there is a need of further research to select the most appropriate intervention to help an individual mother and baby.

Breast Feeding↗
PubMed1988

Systemic lupus erythematosus: learning disability in the male offspring of female patients and relationship to laterality.

Systemic lupus erythematosus (SLE) is a multisystemic disease that predominates in women during the childbearing years. One system frequently affected is the central nervous system. Seizures and psychoses are criteria useful in the diagnosis of SLE. The effects of this disease on disorders of learning and handedness in both patients and first degree relatives are the subject of the present report. Dyslexia and other disorders of learning were present in 45% (24/55) of male offspring of female SLE patients. Ten percent of male siblings of female SLE patients were learning-impaired. Dyslexia and other disorders of learning are also common in women with SLE (dyslexia 12.5%) and men with SLE where the proband is one of two or more cases of SLE in the same family (dyslexia 27.6%). Tests for handedness in the lupus population indicated that there were slightly more patients (mostly women) (p = 0.08) who were lefthanded by the Oldfield laterality test compared to normal volunteers. Handedness did not correlate with the degree of dyslexia in either the patients or their first degree relatives.

Adult↗
PubMed2005

Hand preferences for unimanual and coordinated bimanual tasks in baboons (Papio anubis).

This study examined hand preference in baboons in a sample of 94 subjects for a unimanual task and in a sample of 104 subjects for a bimanual task. For the unimanual task, handedness was assessed by observing simple reaching for grains. For the bimanual task, tubes lined with peanut butter inside were presented to the baboons. The hand and the finger used to remove peanut butter were recorded. Population-level right-handedness was found for the bimanual but not the unimanual task. In addition, test-retest correlations showed consistency in hand use across time for the coordinated bimanual task but not the simple reaching task. No significant effects of age and sex on the direction and strength of hand preferences were found for either task. These are the first evidences of population-level handedness in baboons and the results are discussed in the context of evolutionary theories of cerebral dominance.

Analysis of Variance↗