Handedness is modulated by sex and self-perception

The distribution of handedness is different for men and women. Less pronounced right- or left-handedness in men is well established and often attributed to direct effects of genetic factors. Many studies observing this sex difference assessed handedness via questionnaire. It may therefore be influenced by a sex-specific bias in self-perception. Permanent inadequate self-perceptions are key characteristics of hypochondriasis. The study therefore tested 1017 participants (614 females) on two standard questionnaires to assess handedness and hypochondriasis: the Edinburgh Inventory and the Whiteley Index. Effects of sex, hypochondriac traits and the direction of handedness (left-handers; right-handers) on the degree of handedness (DH; the strength of lateralisation) were tested with multivariate linear regression. In confirmation of previous results, the DH is lower (less pronounced) in right-handed males than right-handed females, but is similar across sexes in left-handers. Regression analyses showed that for right-handers, male sex and higher hypochondriac traits are independent predictors of lower DH. For left-handers, main effects of sex and hypochondriac traits are not significant whereas a significant interaction of these two factors indicates that in left-handed men higher hypochondriac traits are associated with a differentially stronger shift towards lower DH compared to left-handed women. In conclusion, the DH is modulated by sex-specific effects of self-perception for left-handers but not right-handers. The implications of this finding on current theories of the inheritance of handedness are discussed. The assessment of hypochondriac traits might be useful to control response bias in questionnaire-based studies of human handedness.     

Manual asymmetry in a complex coincidence-anticipation task: Handedness and gender effects

This study investigated the effects of handedness and gender on manual asymmetry in the performance of a complex coincidence-anticipation task. Left-handed (N=63) and right-handed (N=93) undergraduate students (78 males, 78 females) were required to press six buttons sequentially in conjunction with visual stimulation provided by a coincidence-anticipation apparatus. Participants were further separated into subgroups based on the degree of hand preference. Timing accuracy (AE, CE, VE) and timing response (IT, MT, AT) were analysed. Results showed that, concerning accuracy, (i) strong left-handers were more accurate than the other groups; (ii) performance with the preferred hand was superior to that of the non-preferred hand; and (iii) males outperformed females. Concerning timing response, (i) the preferred hand was faster than the non-preferred hand for movement time and (ii) males were faster in initiating the movement than females. These findings indicate that coincidence-anticipation competence appears to be influenced by hand preference, performing hand, and gender. In addition, findings are discussed in the framework of the hemispheric functional lateralisation for the planning and organisation of movement execution.     

Language dominance, handedness and sex: Recessive X-linkage theory and test

The possibility is investigated that cerebral dominance for language and handedness share a common X-linkage and that the relation between the two is therefore a function of sex. In particular, an X-linked recessive account is shown to predict an overall configuration of language dominance, handedness and sex within which there is a sex effect in the pattern of language dominance among right-handed but not left-handed people. The recent accurate determination of cerebral dominance among relatively large samples of the general population by means of functional transcranial Doppler ultrasonography makes it possible to test this new theory rigorously, and its parameter-free pattern of predictions is found to be supported.     

Examining the relationship between lateralisation for processing emotional faces,depression, and sex

It is now relatively well established that the right hemisphere is specialised for processing facial emotion; however, there is variability in this pattern of lateralisation. One factor that has been examined is atypical lateralisation in individuals diagnosed with clinical psychological conditions. To date the evidence regarding the neuropsychological processing of emotional stimuli in individuals with depression is contradictory. In this study 160 participants completed the Beck Depression Inventory and the chimeric faces test, a test of lateralisation for the processing of facial expressions of each of the six basic emotions. A negative relationship between depression and lateralisation was found for females only, showing that women with higher depression scores tend to be less strongly lateralised to the right hemisphere, or even lateralised to the left hemisphere, for processing facial emotion. The strength of this relationship also varied across the different emotions with the clearest results for the processing of anger, disgust, and fear. There were no significant findings for males. The possible reasons for there being a sex difference in our findings and an attempt to reconcile the disparate findings within this area of research are discussed.     

Handedness and depression: Evidence from a large population survey

There is a considerable body of research arguing for an association between psychotic disorders and atypical brain lateralisation—where non-right-handedness is usually taken as a marker for the latter. By contrast, there has been less attention given to a possible link between handedness and affective disorders (particularly major depression) and, unlike the case of psychosis, there is no a priori reason for such a link. There are very few studies of the relationship between depression and handedness in normal populations. This paper uses a new large population survey from 12 European countries to measure the association between handedness and depression. It is found that, using three different measures, left-handers are significantly more likely to have depressive symptoms that right-handers. For example left-handers are about 5% more likely to have reported having ever experienced symptoms of depression compared to about 27% of the total sample.     

Hand preference and hand performance: Cross-sectional developmental trends and family resemblance in degree of laterality

The first aim of the study was to compare developmental trends in the degree of laterality (independent of direction) observed in two handedness tasks. The second aim was to assess family resemblance in the degree of laterality using the same two tasks. The sample was comprised of 186 left-handers and 302 right-handers aged from 6 to 66. Some of the sample were members of the same families. Bishop's card-reaching task was used to assess hand preference, and Annett's peg-moving task to assess manual performance. For the card-reaching task, children aged 7 to 10/11 recorded more midline crossings than the other age groups (both younger and older). No general age-related trend was observed for the Annett pegboard. For the card-reaching task, family resemblance was very low and not significant. The degree of laterality, assessed with the peg-moving task, showed a small but significant resemblance in father–offspring pairs (sons and daughters). Putative involvement of a maternally suppressed gene on chromosome 2p12 and of the androgen receptor was discussed.     

Handedness prevalence in the deaf: Meta-analyses

An under-investigated aspect of handedness, a biological proxy for cerebral laterality for language, is its prevalence amongst deaf individuals. We present four sets of meta-analyses on studies measuring handedness prevalence in deaf individuals, comprising 31 data sets and totaling 5,392 participants (4,606 deaf, 786 hearing). Deaf individuals were found to be 2.61 times more likely to be non-right-handed and 2.25 times more likely to be left-handed compared to their hearing counterparts. When handedness was measured by means of manipulative actions, the weighted estimates of handedness prevalence for deaf populations were 17.70% and 14.70% for non-right- and left-handedness respectively; when handedness was measured by means of sign actions, the prevalence was 10.60% and 9.70%, respectively. Yet, when comparing studies that measured handedness in the same deaf individuals using both manipulative and sign actions, no difference was found in their handedness prevalence. This pattern is taken to suggest that the higher prevalence of atypical handedness in the deaf population may be linked to delayed language acquisition.     

Handedness and intellectual achievement: an even-handed look

Evidence from a large-scale study of 11-year olds in Britain suggests that ambidextrous individuals may be disadvantaged in tests of verbal, nonverbal, reading, and mathematical skills relative to right- and left-handers, but this basic finding was not replicated in another study of younger boys in Germany. Here, we present data based on a television show in which members of the public were given an IQ test. Some individuals were also asked to state whether they wrote with the left hand, right hand, or either hand. The data support the earlier finding that ambidextrous individuals perform more poorly than left- or right-handers, especially on subscales measuring arithmetic, memory, and reasoning, and extend that finding to adults.     

Handedness, dichotic-listening ear advantage, and gender effects on planum temporale asymmetry--a volumetric investigation using structural magnetic resonance imaging

Previous research has often examined whether the asymmetrical structure of the planum temporale (PT) represents an anatomical correlate of lateralized language-processing functions, gathering diverging empirical evidence by comparing PT asymmetry in subjects with differing handedness, gender, or speech lateralization. Apart from other methodological problems, direct comparisons between studies are hampered by insufficient assessment and consideration of all three potential determinants of structural cerebral asymmetry. Based on volumetric assessment of structural Magnetic Resonance Imaging (MRI) scans of 104 healthy subjects, the present study replicated earlier observations of an overall leftward PT asymmetry, which was found to prevail irrespective of handedness, gender, or dichotic-listening ear advantage. However, the mean magnitude of this leftward asymmetry was not determined by either one of these factors in itself, but varied depending on their specific combination. A clear correspondence between structural and functional asymmetry was only observed among right-handed males. In this particular subgroup, more pronounced structural asymmetry was associated with an enlarged PT on the left side, while the enhanced leftward asymmetry of female sinistrals resulted from smaller adjusted volumes of their right PT. The existence of such complex interactions suggests that future research in this area can only be expected to overcome past inconsistencies by adequately considering handedness, gender, and speech lateralization.     

Interbrains cooperation: Hyperscanning and self-perception in joint actions

The aim of the present study was to investigate the neural bases of cooperative behaviors and social self-perception underlying the execution of joint actions by using a hyperscanning brain paradigm with functional near-infrared spectroscopy (fNIRS). We firstly found that an artificial positive feedback on the cognitive performance was able to affect the self-perception of social position and hierarchy (higher social ranking) for the dyad, as well as the cognitive performance (decreased error rate, ER, and response times, RTs). In addition, the shared cognitive strategy was concurrently improved within the dyad after this social reinforcing. Secondly, fNIRS measures revealed an increased brain activity in the postfeedback condition for the dyad. Moreover, an interbrain similarity was found for the dyads during the task, with higher coherent prefrontal cortex (PFC) activity for the interagents in the postfeedback condition. Finally, a significant prefrontal brain lateralization effect was revealed, with the left hemisphere being more engaged during the postfeedback condition. To summarize, the self-perception, the cognitive performance, and the shared brain activity were all reinforced by the social feedback within the dyad.     

Handedness and schizotypy in non-psychotic relatives of patients with schizophrenia

Existing studies have found the relationship between handedness and schizotypy to be inconsistent, and had limited generalisability since only highly homogeneous groups have been investigated. This study aimed to examine the relation between handedness and the four schizotypal factors identified from a previous confirmatory factor analysis in a population of high familial loading for schizophrenia. Study participants consisted of non-psychotic first-degree relatives (850 parents and 334 siblings) of sib-pairs who were co-affected with schizophrenia. All participants were interviewed with the Diagnostic Interview for Genetic Studies, which contains a section of the modified Structured Interview for Schizotypy, and the Annett handedness questionnaire. Both categorical and continuous indicators for handedness were examined. Non-right-handed siblings of schizophrenia patients displayed more positive schizotypal features than their right-handed counterparts when the two-way Annett's handedness classification was adopted. No association was found when handedness was treated as continuous. The relationship between handedness and schizotypy was insignificant for parents probably due to the strong social pressure against left-handedness. We concluded that categorical non-right-handedness was associated with positive schizotypy in non-psychotic siblings of schizophrenia patients. The results indicate that an atypical cerebral lateralisation underlying non-right-handedness may be also a contributing factor to positive schizotypy.     

Handedness, eyedness and nasal cycle in children with autism

OBJECTIVE: Autism is referred to as cerebral lateralization abnormality. In this study, the possible relationships among handedness, eyedness and nasal cycle in autism have been investigated. MATERIALS AND METHODS: Thirty-seven children with autism and 20 controls were included in the study. The patient group included 27 boys and 10 girls who ranged in age from 5 to 20 years. For hand preference, hand used to write and throw a ball was accepted as dominant hand. For eye preference or dominance, eye used to look through keyhole of a door was accepted as dominant eye. Nasal dominance was assessed by a method of measuring the nasal airflow. RESULTS: The rates of left-handedness and left-eyedness were higher in children with autism compared to normal populations. A majority of children with autism had left nasal dominance. CONCLUSION: Autism and early language impairment may be associated with left handedness, eyedness and nasal dominance.     

Handedness, laterality and the size-weight illusion

The goal of this study was to determine how handedness and lifting hand influence the way in which we lift objects and perceive their weights. To this end, we examined the fingertip forces and perceptual judgements of 30 left-handers and 30 right-handers during lifts of specially constructed ‘size-weight illusion’ (SWI) cubes with their left and right hands. All participants completed a series of lifts first with one hand and then the other, so we could additionally examine asymmetries in the retention and transfer of force information between the limbs. Right-handers experienced a larger illusion with their left hand than they did with their right hand, whereas left-handers showed no such asymmetry in their illusions. The perceptual illusion’s independence from the application of fingertip force was highlighted by an unexpected lack of asymmetry in terms of fingertip force scaling. Left- and right-handers showed no dominant hand advantage in this task – they were no more skilled at correcting their fingertip force errors with their preferred hand than they were with their non-preferred hand. In addition, although no asymmetries were observed with regard to the most efficient direction of intermanual transfer, the right-handed individuals transferred force information between the hands more effectively than the left-handers. Overall, these findings indicate that hand dominance does not affect the control of the fingertip forces, suggesting that existing models of cerebral laterality must be re-visited to consider kinetic (i.e., related to forces), as well as kinematic (i.e., related to movement) variables.     

女性急性脑梗死患者内源性性激素和血脂变化的研究

目的 探讨女性急性脑梗死（ＡＣＩ）患者血清性激素水平的变化及其对血脂的影响。方法 应用酶联免疫吸附法、酶比色法和直接测定法检测女性ＡＣＩ患者的血清雌二醇（Ｅ２）、睾酮（Ｔｅ）、Ｅ２／Ｔｅ及血脂含量并与健康人比较。结果 女性ＡＣＩ患者有性激素失衡及血脂异常,Ｅ２、Ｔｅ、ＨＤＬ含量降低,以Ｅ２降低更为明显（Ｐ〈０．０１、Ｐ〈０．０５、Ｐ〈０．０５）,而Ｅ２／Ｔｅ无显著性差异（Ｐ〉０．０５）,ＬＤＬ、ＴＣ含量较对照组明显升高,均有显著性差异（Ｐ〈０．０１）。结论 性激素水平紊乱是女性急性脑梗死患者的危险因素之一,并影响脂质代谢。     

Handedness for grasping objects and pointing and the development of language in 14-month-old infants

The goal of this study was to evaluate the relationship between object-related handedness and handedness for communicative gestures. We observed 22 infants aged 14 months on a baby laterality test consisting of grasping objects in different conditions, on a pointing task with targets placed out of reach at different spatial positions from left to right, and on word understanding and word production. Results show that 77% of infants pointed to the left, middle, and right targets. The majority of infants were right-handed for pointing—except for the far left target—and, to a lesser extent, for grasping objects, but there was no significant relation between the two measures of handedness. The frequency of pointing tended to be related to the number of words understood, and infants right-handed for pointing understood and produced significantly more words than non-right-handed pointers. These results are interpreted as confirming the link between pointing and language development, and as showing that communicative gesture lateralisation is not a mere consequence of object-related handedness, at least during development. Whether lateralised communicative gesture reinforces a pre-existing tendency to use the right hand to interact with objects remains an open question.     

Handedness in preterm born children: a systematic review and a meta-analysis

It has been proposed that left and/or non-right handedness (NRH) is over-represented in children with a history of preterm birth because such births are associated with a greater incidence of insult to the brain. We report an approximate two-fold increase in left and/or non-right handedness based on a systematic search of the literature from 1980 to September 2010 for English-language articles reporting handedness status in preterm children compared with fullterm controls either as a main focus of the study or as a secondary finding. In total, thirty articles met the inclusion criteria. However, there was a great variation between the included studies in terms of objectives, population characteristics, sample size and methodologies used. While the majority of studies reported a higher incidence of NRH in preterm than fullterm children, this was not a consistent finding. A quality assessment was made to explore the differences in overall study quality and handedness assessment methodology between studies. A random-effects model meta-analysis was then performed to estimate the accumulated effect of preterm birth on handedness (18 studies; 1947 cases and 8170 controls). Preterm children displayed a significantly higher occurrence of NRH than fullterm children (odds ratio [OR]: 2.12; 95% confidence interval [CI]: 1.59-2.78). Sources of heterogeneity were investigated by supplementary meta-analyses considering studies with high or low overall and handedness assessment quality. Publication bias was assessed by Egger's test of the intercept and Duvall and Tweedie's trim-and-fill method. The outcomes of these procedures did not jeopardize the overall finding of reliably increased OR for NRH in preterm children. The present review suggests that a preterm birth is indeed associated with a greater than two-fold likelihood of NRH. Several studies also explored the relationship between handedness and neuropsychological functioning (cognition mainly) with an array of methods. Although not without disagreement, this association was found to be concordant. Studying handedness in preterm children, therefore, is a potentially important index of hemispheric organization and cognitive and sensory-motor functions following neurodevelopmental disturbance.     

Handedness and lower face variability: Findings in three national surveys

Lower face variability in modern humans has been associated with a series of phenotypic characteristics including body architecture and handedness. The aim of this study was to provide a systematic review of lower face variability and handedness in national health surveys conducted in the United States. Three informative surveys with a total of 13,663 participants were identified. Lower face variability was described as one of six facial phenotypes and related to handedness using logistic regression models while adjusting for sex, ancestry, geography, and income. The results on 13,536 participants with complete information showed that bilateral retrognathism—a marker for a lower face phenotype characterized by a convex facial profile and slender jaws—was associated with a 25% increased odds for non-right-handedness (odds ratio, 1.250; 95% confidence interval: 1.076–1.453, p-value?相似文献   

Episodic odor memory: influences of handedness, sex, and side of nose

It is not known whether, or to what degree, odor memory is influenced by lateralized brain processes. In this study, we administered a 12-item match-to-sample odor memory test separately to the left and right sides of the nose of 30 left- and 30 right-handed subjects of equivalent age, sex distribution, and overall general smell ability. For each test item, one of three delay intervals (10-, 30-, and 60-s) was interspersed between smelling the target stimulus and smelling the first of four response alternatives. Women, but not men, performed significantly better on the left than on the right side of the nose, conceivably reflecting greater reliance upon left-hemisphere semantic processes. Subjects who received the first test on the right side of the nose outperformed those who received the first test on the left side of the nose. As in previous work, an age-related decrement in odor memory test scores was present. These data contribute to the debate on the role of lateralized brain processes in episodic odor memory, and suggest that performance on a standardized match-to-sample odor memory task is influenced by a number of interacting factors.     

Handedness and developmental coordination disorder in Portuguese children: Study with the M-ABC test

This study aimed to examine the probable developmental coordination disorder (DCD) and to identify differences in motor performance according to handedness, sex and age in typically developing Portuguese children not engaged in out-of-school sports. The Movement Assessment Battery for Children (M-ABC) was applied to a convenience sample of 154 right-handed and 119 left-handed children (n = 273), aged 4–12 (mean age = 7.96 years, SD = 2.38). The results suggest that the occurrence rate of probable DCD was 25.3% for right-handers and 36.1% for left-handers. This study showed a significant effect of handedness in age band 2, left-handers exhibited a higher prevalence of probable DCD than right-handers. Sex produced a significant effect, with girls performing better in manual dexterity in age band 1 and boys performing better in ball skills in age bands 2 and 3. The lower motor performances were observed in older children. These findings reinforce for Portuguese children and particularly for left-handers, the need for further investigation involving longitudinal studies and children of different handedness in the motor coordination domain. Moreover, we highlight the importance of developing physical education programmes that emphasize motor coordination parameters, especially in left-handed children.     

Of mice and men - and lopsided birds

The article by Zucca and Sovrano (2008, this issue) represents part of a new wave of studies of lateralization in nonhuman species. This work is often in conflict with earlier studies of human cerebral asymmetry and handedness, and the associated claim that these asymmetries are uniquely human, and perhaps even a result of the "speciation event" that led to modern humans. It is now apparent that there are close parallels between human and nonhuman asymmetries, suggesting that they have ancient roots. I argue that asymmetries must be seen in the context of a bilaterally symmetrical body plan, and that there is a balance to be struck between the adaptive advantages of symmetry and asymmetry. In human evolution, systematic asymmetries were incorporated into activities that probably are unique to our species, but the precursors of these asymmetries are increasingly evident in other species, including frogs, fish, birds, and mammals - especially primates.