Non-right Handedness Research Articles

The relation between lateralisation, early start of training, and amount of practice in musicians: A contribution to the problem of handedness classification

This study investigates the influence of extensive bimanual training in professional musicians on the incidence of handedness in the most basic form of right-handedness (RH) and non-right-handedness (NRH), according to Annett's “right shift theory”. The lateralisation coefficients (LCs) of a total sample of 128 bimanually performing music students were calculated for speed, regularity, and fatigue of tapping by using the speed tapping paradigm. Additionally, the accumulated amount of practice was recorded by means of retrospective interviews. The proportion of designated right-handers (dRH) and non-right-handers (dNRH) in hand performance was identified by binary logistic regression from LCs. A proportion of 30.8% designated NRH in the group of musicians was found, while in the control group of non-musicians (matched for age range) a proportion of 21.7% designated NRH was observed. Incidence of dNRH was higher in string players (35.6%) than in pianists (27.1%). As an effect of the extensive training of the left hand, tapping regularity increased and tapping fatigue decreased among those participants who evidenced an increased amount of accumulated practice time on the instrument. However, speed difference between hands (as indicated by LCs) remained uninfluenced by bimanual training. This finding is in contrast to those of Jäncke, Schlaug, and Steinmetz (1997). Finally, our study provides a more reliable (statistical) classification as an external criterion for future genetic analyses of handedness.

Safety of ultrasonography in pregnancy: WHO systematic review of the literature and meta‐analysis

In the context of the planned International Society of Ultrasound in Obstetrics and Gynecology-World Health Organization multicenter study for the development of fetal growth standards for international application, we conducted a systematic review and meta-analysis to evaluate the safety of human exposure to ultrasonography in pregnancy. A systematic search of electronic databases, reference lists and unpublished literature was conducted for trials and observational studies that assessed short- and long-term effects of exposure to ultrasonography, involving women and their fetuses exposed to ultrasonography, using B-mode or Doppler sonography during any period of pregnancy, for any number of times. The outcome measures were: (1) adverse maternal outcome; (2) adverse perinatal outcome; (3) abnormal childhood growth and neurological development; (4) non-right handedness; (5) childhood malignancy; and (6) intellectual performance and mental disease. The electronic search identified 6716 citations, and 19 were identified from secondary sources. A total of 61 publications reporting data from 41 different studies were included: 16 controlled trials, 13 cohort and 12 case-control studies. Ultrasonography in pregnancy was not associated with adverse maternal or perinatal outcome, impaired physical or neurological development, increased risk for malignancy in childhood, subnormal intellectual performance or mental diseases. According to the available clinical trials, there was a weak association between exposure to ultrasonography and non-right handedness in boys (odds ratio 1.26; 95% CI, 1.03-1.54). According to the available evidence, exposure to diagnostic ultrasonography during pregnancy appears to be safe.

Mixed handedness prevails among children and adolescents with infantile asthma and diabetes

Non-right handedness has been associated with allergic diseases and asthma. Infantile diabetes, too, has been associated with non-right handedness but, to date, data are more consistent on a link between left handedness and asthma than on diabetes. We surmised that mixed handedness, as an indicator of neurodevelopmental disturbance of brain laterality, rather than left handedness is more prevalent among children with asthma and diabetes mellitus. A total of 100 families with a child or an adolescent diagnosed with infantile asthma (n = 50) or diabetes mellitus type 1 (n = 50) attending the Paediatric Clinic of the 'Brotzu' Hospital in Cagliari (Italy) in 2006 agreed to participate in the study. The Annett Hand Preference Questionnaire was used to test handedness. Compared with 99 same-age and -sex controls, cases were marginally less likely to be right handed (71% vs. 86%; OR = 0.82, 95% CI = 0.54-1.25), and statistically more likely to be mixed handed (20% vs. 6%; OR = 3.30, 95% CI = 1.27-8.56) than controls: chi(2) = 8.84, d.f. = 2, p = 0.01. Children with asthma or diabetes did not differ from controls by season of birth; however, mixed-handed (n = 12, 46%) and left-handed (n = 6, 35%) children were statistically more likely to be born in winter as against the other seasons than those who were right handed (n = 36, 23%). Severity was also marginally related to the chance of being classified as non-right handed. People with a genetic predisposition to immune disorders could be more likely to have been negatively affected by infection and inflammation during fetal life, thus developing a deviation in handedness during neurodevelopment, as well as suffering the consequence of disordered immunity during childhood, such as allergic reactions (asthma) and immune-mediated damage to specific internal organs (diabetes type 1).

Medial Position and Counterclockwise Rotation of the Parietal Scalp Hair-Whorl as a Possible Indicator for Non-Right-Handedness

The objective of our study was to assess the association between position and swirling direction of the parietal whorl (PW) and handedness. In 519 patients of a pediatric practice, PWs were located and the swirling direction determined. Of those patients, handedness could be specified in 217. The right-sided PW (n = 347; 70.8%) and the clockwise (CW) swirling type (n = 411; 83.9%) of all participants were predominant in children with one PW. Non-right-handedness (NRH) was found in 40 (18.4%). Medial position of the whorl per se increases the chance for NRH, indifferent of the swirling direction. In patients with counterclockwise (CCW) swirling, the chance of NRH increased 3.5-fold for the right-sided, 5.4-fold for the left-sided, and 12.9-fold for the medial-positioned whorl. We conclude that NRH is associated with the position (medial!) and the swirling direction (CCW!) of the PW.

Neurodevelopmental Correlates of Paraphilic Sexual Interests in Men

The etiology of anomalous, or paraphilic, sexual preferences in men is unclear although a growing literature points to their prenatal neurodevelopmental ontogenesis. The present study explored whether this was also apparent in a community sample of 200 heterosexual men by examining their sexual fantasies using the Wilson Sex Fantasy Questionnaire (WSFQ) and several demographic and somatic neurodevelopmental markers, including sibling sex composition, handedness, maternal and paternal age at birth, second to fourth finger length ratios, and fluctuating asymmetry of finger lengths and wrist widths. Responses to the WSFQ were used to quantify the extent of paraphilic interest by computing a variance-quotient (or VQ) previously shown to differentiate paraphilic from conventional heterosexual males. High paraphilic scorers had a significantly greater number of older brothers, higher right-hand 2D:4D, and a trend for lower Edinburgh Handedness Inventory (EHI) scores compared to low-paraphilic scorers. Correlational analysis revealed a significant positive association of VQ scores with number of older brothers and significant negative associations with number of younger brothers and EHI scores (elevated paraphilic interests were correlated with elevated non-right handedness). Correlations between VQ scores and other variables were not significant. It is suggested that processes such as developmental instability and maternal immunity may play a role in variant sexual preferences among otherwise healthy heterosexual men.

Creativity and Psychopathology

Creative people have been found to score higher on psychopathologic scales in standardized tests, particularly on the scales that measure traits of psychoticism, and to be more likely to report an excess of nonright handedness compared with controls. However, results are inconsistent across surveys and methodologies, and the contribution of substance abuse has rarely been measured. In this study, 80 creative artists were compared with 80 matched noncreative controls on the Annett Hand Preference Questionnaire (HPQ), the Peters et al. Delusions Inventory, and the General Health Questionnaire. Creative artists were statistically more likely to admit the use of the left hand on the HPQ, with more widespread left hand use reported by artists involved in the creative activities traditionally associated with the right hemisphere (music and painting). They also scored higher on the Peters et al. Delusions Inventory independently from the level of psychopathology (measured with the General Health Questionnaire), from their laterality score (measured with the HPQ), and from their higher use of both licit and illicit drugs.

Handedness and schizotypy in non-clinical populations: Influence of handedness measures and age on the relationship

This study aimed to evaluate the relation of handedness to schizotypal personality, with the influence of different handedness measures and age on the relationship investigated as well among representative samples of school students and community adults in Taiwan, where social pressure against certain left-handed actions was strong. In a total of 175 primary school students, 1020 junior high-school students, and 342 adult participants aged 20 to 65 years, all the participants completed the 12-item Annett handedness questionnaire, and the latter two groups further completed the Schizotypal Personality Questionnaire (SPQ) and the Perceptual Aberration Scale (PAS). There was a trend of increasing non-right handedness with younger age groups. Two classification methods in handedness, Annett's or Briggs-Nebes’ three-category classification, led to very different frequency distribution and relation to schizotypy. For the adolescents, either Annett's classification or quantitative measures (Hand Preference Index and either-hand use scores) in handedness exhibited an association with schizotypy, whereas for the adults the either-hand use score was the only measure that did so. In contrast, no such difference was found using the Briggs-Nebes’ classification method. The association of the non-right or mixed handedness was more consistent and of greater magnitude with the positive aspect of schizotypy, especially the PAS and the Cognitive-perceptual Dysfunction of the SPQ. The results highlight the potential of adolescents for future investigation on certain common causes underlying atypical cerebral lateralisation and positive schizotypy.

Genetic and Environmental Influences on the Handedness and Footedness in Japanese Twin Children

The purpose of this study was to examine the genetic contribution to handedness and footedness in childhood using one of the largest available databases of Japanese twins. The participants were 1131 twin pairs, 1057 males and 1205 females, of 11 or 12 years of age (6th grade of secondary school in the Japanese education system). All data were gathered by questionnaire. The prevalence of left (nonright) handedness was 15% in males and 13% in females. The prevalence of left (nonright) footedness was 13% in males and 11% in females. The similarities between twin pairs, estimated by concordance rates and tetrachoric correlations, suggested a slight genetic effect on male handedness, no genetic effect on female handedness, and no genetic effect on footedness in either sex. Structural equation modeling showed small genetic factors (11%) in male handedness and no genetic factors in female handedness. As to footedness, no genetic factors were observed in either sex. The effects of nonshared environmental factors were large (85%) in males and moderate (44%) in females. Moreover, handedness and footedness tended to be concordant irrespective of sex, with polychoric correlations over r = .70. The results of bivariate genetic analyses were not necessarily satisfactory. For males, no model fit. For females, shared and nonshared environmental factors explained the concordance of handedness and footedness. It was concluded that the genetic effects on handedness and footedness are relatively small, as is their association; moreover, considerably large twin samples are needed to obtain stable and appropriate results.

Hair whorls and handedness: Informative phenotypic markers in nonsyndromic cleft lip with or without cleft palate (NS CL/P) cases and their unaffected relatives

Cleft lip with or without cleft palate (CL/P) is a complex disorder with a range of phenotypic manifestations and a birth prevalence that varies by population (1/500-1/2,000). Investigators have postulated that CL/P cases may have abnormal brain development, citing structural brain differences, and cognitive impairments in affected individuals. Previously, increased levels of non-right handedness (NRH), a marker for abnormal brain lateralization, have also been demonstrated in CL/P cases. Atypical hair whorls, more direct markers of altered brain development, may be related to NRH. To date, neither hair whorl patterns nor their relationship to NRH have been studied in a CL/P population. In the current study, we investigate the hypothesis that altered brain development is part of the phenotypic spectrum of NS CL/P by assessing NRH and atypical hair whorls in CL/P families. The study population included 49 nonsyndromic CL/P cases and 116 of their unaffected relatives; 21.8% of the study population was NRH compared to the 10% population estimate (P < 0.0001). Counter-clockwise hair whorls (CCW) were found in 12.7% of all subjects compared to a population rate of 9.9 %. Of all subjects, 11% of the NRH individuals had CCW, which was similar to the frequency of CCW in right-handed individuals. Approximately 80% of the whorls were placed on either the right or center of the scalp. No significant associations were found between the type of cleft and handedness, hair whorl rotation, or placement. These results suggest that certain phenotypic markers of abnormal brain development may comprise part of the extended phenotype of orofacial clefting.

Fluctuating asymmetry, second to fourth finger length ratios and human sexual orientation

Sexual orientation in humans may be influenced by levels of prenatal sex steroids which canalise neurodevelopment along sex-typical (heterosexual) or sex-atypical (homosexual) lines. Some evidence for sexual-orientation-related differences in putative somatic markers of prenatal sex hormones supports this view. A competing theory asserts that human homosexuality is due to developmental instability (DI) because it represents a shift from the species-typical pattern of heterosexual orientation. Evidence for elevated rates of non-right handedness among homosexuals provides limited support for this account. The current study tested both theories by examining nine bilateral somatic traits in 120 healthy heterosexual and homosexual men and women in order to compute second to fourth finger length ratios (2D:4D), a measure ascribed to levels of prenatal sex steroids, and fluctuating asymmetry (FA), a measure of DI. Homosexual men and women had significantly lower right hand 2D:4D ratios (even after controlling for handedness, height and weight differences) in comparison to heterosexuals, but sexual orientation did not relate to composite FA scores. The findings constrain the number of possible neurodevelopmental pathways responsible for sexual orientation in humans.

Hand preference and hand skill in families with schizophrenia

Direction and degree of handedness in humans are variable between individuals and thought to be in part inherited. Several studies have shown an increase in non-right handedness among patients with schizophrenia, and some have included unaffected relatives. The present study was designed to determine whether reduced right handedness is more frequent among individuals with schizophrenia as compared with their well relatives and whether it clusters within families having multiple ill members. A total of 259 families comprising 418 individuals diagnosed with schizophrenia or schizoaffective disorder, 54 individuals with other psychoses, 145 family members with depression and other minor diagnoses, and 288 unaffected individuals were included. Hand preference was assessed by the Annett Scale and right relative to left hand skill measured using the Tapley-Bryden test. For all assessments of hand preference and hand skill, females were significantly more lateralised towards the right than males. Those individuals with schizophrenia or schizoaffective disorder had significantly less right hand preference than their unaffected relatives when measured as a quantitative index of items from the Annett Scale (p = .019), but not categorically (right, left or mixed). In contrast, there was no difference in hand skill between diagnostic groups. Hand preference was significantly correlated among male-male affected sibling pairs (p = .01) and similar results were found for hand skill among the total group of affected pairs (p = .001). Although these results only partially support a relationship between handedness and schizophrenia, they nevertheless draw attention to sex differences in hand preference and the familial aspects of hand preference in this disorder. More direct approaches to the genetics of cerebral dominance and psychosis are required.

Sinistrality in schizophrenia

Sinistrality characterized by an excess of non-right handedness has been reported in schizophrenic patients. Two factors, sex and kind of evaluation of handedness have contributed to major discrepancies across studies. Aim: The hypothesis tested was that schizophrenic patients show a sinistral shift in handedness compared to controls taking into account the sex and using a continuum scoring system for evaluating handedness. Methods: Seventy-three (73.1% males) schizophrenic patients (DSMIV) and 81 (64.2% males) controls were evaluated with the Edinburgh Handedness Inventory (EHI [Neuropsychologia, 9 (1971) 97]). Results: The EHI score mean difference between patients with schizophrenia and control group was not significant when sex was taken into account. Conclusion: Schizophrenic patients taken as a whole did not show a sinistral shift in handedness even if the sex and the continuum score for handedness were considered.

Handedness, criminality, and sexual offending

A very large database was used to investigate whether men with a history of criminality and/or sexual offending have a higher incidence of nonright-handedness (NRH) relative to a control sample of nonoffender men. The sample ( N>8000) comprised interviews by investigators at the Kinsey Institute for Sex and Reproduction in Indiana. The general offender group and a subsample of sex offenders (e.g. pedophiles) had a significantly higher rate of NRH relative to the control (nonoffender) men. In addition, evidence was found that the general criminality/NRH relationship might result from increased educational difficulties that some nonright-handers experience. In contrast, education was unrelated to the handedness/pedophilia relationship, suggesting that there may be a different mechanism underlying the handedness/pedophile relationship than the handedness/(general) criminality relationship. Finally, as a cautionary note, it is stressed that the effects are small and that NRH should not be used as a marker of criminality.

Associations among dissociative experiences, handedness, and demographic variables in a nonclinical population.

Handedness is considered an indirect marker for bilateral language capacity in the brain. The Edinburgh Inventory for Handedness and the Dissociative Experiences Scale (DES) were administered to 297 nonclinical volunteers. Female sex, young age, and non-right handedness accounted for 24% of the total variance on the DES, including both pathological and nonpathological dissociative experiences. This is consistent with the hypothesis that cerebral lateralization indicating handedness is a predisposing factor for dissociative episodes especially in female subjects.

Predicting Combinations of Left and Right Asymmetries

This paper explains how combinations of asymmetries for pairs of laterality variables may be predicted. It shows that many pairs combine as expected by chance, plus the influence of the RS+ gene hypothesised by Annett (1978, 1985). These include: eye dominance with writing hand, with throwing hand, and with foot for kicking; nonright handedness with planum temporale asymmetry, with asymmetry of the parietal operculum, and the association between these two anatomical asymmetries. Handedness for writing and throwing, and hand and foot preferences are more strongly associated, suggesting the presence of an additional influence. The reliability of the present analyses was supported by replication, especially in findings for hand preferences for writing and throwing described by Gilbert and Wysocki (1992). The relative frequencies of discordant patterns of preference, LR (writing, throwing) versus RL, are a function of the frequencies of the two variables in the population. These differ between age groups and also with the classification of ‘either’ hand preferences. Patterns of preference for writing, throwing and eye-dominance (RRR, RRL etc) are related in an orderly manner to differences between the hands for peg moving time. The success of the present application of the RS theory strengthens the argument that individual differences for hand preference depend on a continuous distribution of asymmetry, not on the ‘types’ commonly assumed in the literature.

Excess of non-right handedness among individuals with intellectual disability: experimental evidence and possible explanations.

Seventy-three subjects with mild and moderate intellectual disability (ID) of an unknown/idiopathic nature, who had no record of specific deficits in motor control, and 73 normal controls, matched for chronological age and sex, underwent evaluation of handedness. The results confirmed the previously reported excess of non-right handedness among subjects with ID, and suggested that this finding might be indicative of a deviant cerebral organization or atypical lateralization of cerebral representation of function in this group. However, it was noted that further research is needed to clarify how far this is a function of level of motor skill and how far is a syndrome-specific pathological phenomenon.

Routine ultrasound screening in pregnancy and the children's subsequent handedness

Objective: To study a possible association between ultrasound screening in early pregnancy and altered cerebral dominance measured by the prevalence of non-right handedness among children, particularly boys. Methods: Follow-up of 8 to 9 year old children to women who participated in a randomised controlled trial on ultrasound screening during pregnancy in 1985–1987. The children were followed up through a questionnaire sent to their mothers. The dominant hand of the child was assessed by eleven questions. The dominant foot by one question. Results: No differences were found in non-right handedness between children in the screening and non-screening group. In separate analyses on ultrasound exposure and non-right handedness among boys a significant difference was found (odds ratio 1.33; 95% confidence interval 1.02–1.74). Conclusion: This study could not rule out a possible association between non-right handedness among boys and ultrasound exposure in early fetal life. The association was, however, confined to analyses comparing exposed and non-exposed boys and no associations were found when the comparisons were performed according to the randomised groups.

Mixed handedness and schizotypal personality in a non-clinical sample—The role of task demand

The present study examined the link between schizotypal personality traits and manual hand preference for ‘skilled’ and ‘less skilled’ tasks in a non-clinical sample of college students. The results are consistent with previous findings regarding the higher proportion of non-right handedness among college students who score high on the Schizotypal Personality Questionnaire (SPQ), a self-report measure of schizotypal traits. A significant correlation between hand preference for ‘skilled’ tasks and particular schizotypal traits associated with cognitive—perceptual deficits was noted. The analyses also indicate that unlike schizophrenic patients who exhibit a higher incidence of mixed handedness for ‘less skilled’ tasks (see Nelson, Satz, Green & Cicchetti, 1993), individuals who score high on the SPQ exhibit a higher incidence of non-right handedness for ‘skilled’ tasks. Examination of the stability of non-right handedness over time in this population indicates that at least some of the schizotypes did not maintain their non-right handedness upon retesting, supporting the role of situational variables on lateral dominance in this population.

Predicting Rate of Cognitive Decline in Probable Alzheimer's Disease

Recent attempts to identify predictors of rate of decline in Alzheimer's disease (AD) have been extremely variable in choice of outcome variables, predictor variables tested, timing of assessments, and statistical approaches. In this study, a random effects regression model was applied to seek predictors of decline on the Mini-Mental State Exam in 132 patients with probable AD reassessed every 6 months for up to 7.5 years. Potential predictor variables at baseline were of three types: patient characteristics, clinical variables, and cognitive performances. The final multivariate analysis indicated that the following characteristics predicted more rapid cognitive decline: more education, history of dementia in a first degree relative, non-right handedness, better performances on Boston Naming Test, Gollin Incomplete Figures Test, and Benton Visual Retention Test-Delay, and worse performances on Responsive Naming Test, WAIS-R Block Design, and Benton Visual Retention Test-Copy.

Nonright‐handedness, central nervous system and related pathology, and its lateralization: A reformulation and synthesis

A theoretical analysis of the associations between nonright‐handedness (NRH) and various neurodevelopmental disorders, psychopathology, and related medical conditions is presented. Fourteen disorders and conditions are reviewed in which elevated NRH has been alleged. Impaired noradrenergic activity and, to a lesser extent, serotonergic dysfunction are common to most of these disorders but are not always associated with elevated NRH. In contrast, dysfunction of the labyrinth, its neural projection areas, or both, apparently exists in all cases involving a proven elevation in NRH, but not in other disorders associated with neurochemical imbalances but normal percentages of right‐handedness. It is theorized that inputs from the vestibular system to the locus coeruleus, raphe nucleus, and other brainstem structures are critical to the development of motoric dominance and the lateralization of monoaminergic activity in the central nervous system, whereas the contribution of vestibular dysfunction to overall central nervous system neurochemical imbalances is considerably less significant.