Direction Of Hand Preference Research Articles

Hand preference and the corpus callosum: Is there really no association?

Originating from a series of morphometric studies conducted in the 1980s, it appears a widely held belief in cognitive neuroscience that the corpus callosum is larger in left or mixed handers than in right handers (RH). However, a recent meta-analysis challenges this belief by not finding significant differences in corpus callosum size between handedness groups. Yet, relying on the available published data, the meta-analysis was not able to account for a series of factors potential influencing its outcome, such as confounding effects of brain size differences and a restricted spatial resolution of previous callosal segmentation strategies. To address these remaining questions, we here analysed N = 1057 participants' midsagittal corpus callosum of from the Human Connectome Project (HCP 1200 Young Adults) to compare handedness groups based on consistency (e.g., consistent RH vs. mixed handers, MH) and direction of hand preference (e.g., dominant RH vs. dominant left handers). A possible relevance of brain-size differences was addressed by analysing callosal variability by both using forebrain volume (FBV) as covariate and utilising relative area (callosal area/thickness divided by FBV) as a dependent variable. Callosal thickness was analysed at 100 measuring points along the structure to achieve high spatial resolution to detect subregional effects. However, neither of the conducted analyses was able to find significant handedness-related differences in the corpus callosum and the respective effect-sizes estimates were small. For example, comparing MH and consistent RH, the effect sizes for difference in callosal area were below a Cohen's d = 0.1 (irrespective of how FBV was included), and narrow confidence intervals allowed to exclude effects above |d| = 0.2. Analysing thickness, effect sizes were below d = 0.2 with confidence intervals not extending above |d| = 0.3. In this, the possible range of population effect sizes of hand preference on callosal morphology appears well below the effects commonly reported for factors like age, sex, or brain size. Effects on cognition or behaviour accordingly can be considered small, questioning the common practise to attribute performance differences between handedness groups to differences in callosal architecture.

Performance on inhibitory tasks does not relate to handedness in several small groups of Callitrichids.

Brain lateralization, a trait ubiquitous in vertebrates and invertebrates, refers to structural differences between the left and right sides of the brain or to the left and right sides controlling different functions or processing information in different ways. Many studies have looked into the advantages of lateralized brains and discovered that cerebral lateralization confers a fitness advantage. Enhancing cognitive ability has been proposed as one of the potential benefits of the lateralized brain, however, this has not been widely validated. In this study, we investigated the handedness of 34 subjects from four groups of Callitrichids, as well as their performance in two inhibitory control tasks (the revised A-not-B task and the cylinder task). The subjects had strong individual hand preferences, and only a few zoo-born individuals were ambidextrous. Sex and generation influence the strength of hand preference. In the cylinder task, the subjects showed differences between groups, and the performance of the second-generation was better than that of the first-generation. We found that neither the strength of hand preferences (ABS-HI) or direction of hand preferences (HI) was linked with success on the two inhibitory tasks. That is, we were unable to support the enhanced cognitive function hypothesis. We believe that individual ontogeny and the type of cognitive task have an impact on the support of this hypothesis. The advantages of lateralized brain may be reflected in tests that require multiple cognitive abilities.

A longitudinal examination of perinatal testosterone, estradiol and vitamin D as predictors of handedness outcomes in childhood and adolescence

ABSTRACT The developmental origins of handedness remain elusive, though very early emergence suggests individual differences manifesting in utero could play an important role. Prenatal testosterone and Vitamin D exposure are considered, yet findings and interpretations remain equivocal. We examined n = 767 offspring from a population-based pregnancy cohort (The Raine Study) for whom early biological data and childhood/adolescent handedness data were available. We tested whether 18-week maternal circulatory Vitamin D (25[OH]D), and testosterone and estradiol from umbilical cord blood sampled at birth predicted variance in direction of hand preference (right/left), along with right- and left-hand speed, and the strength and direction of relative hand skill as measured by a finger-tapping task completed at 10 (Y10) and/or 16 (Y16) years. Although higher concentrations of Vitamin D predicted more leftward and less lateralized (regardless of direction) relative hand skill profiles, taken as a whole, statistically significant findings typically did not replicate across time-point (Y10/Y16) or sex (male/female) and were rarely detected across different (bivariate/multivariate) levels of analysis. Considering the number of statistical tests and generally inconsistent findings, our results suggest that perinatal testosterone and estradiol contribute minimally, if at all, to subsequent variance in handedness. Vitamin D, however, may be of interest in future studies.

Lion-tailed macaques show a stable direction and reinforcement of hand preference in simple reaching tasks over several years

Research on hand preference in non-human primates provides information about the evolutionary origin of population-level bias of human handedness. Human hand preference has been shown to remain stable throughout an individual's lifespan. However, the stability of hand preference and its change with age in non-human primates remains questionable. We recorded hand use in lion-tailed macaques (Macaca silenus) during simple reaching tasks in three time periods over six years. We tested the effect of age and body posture on the direction and strength of hand preference in 23 observed individuals. In a subsample of 13 individuals followed for two or three subsequent time periods, we assessed the stability of hand preference across study periods. The direction of hand preference was highly stable; we detected no individuals changing from a left- to right-, or right- to left- preference and repeated quantitative measures of hand preference were correlated among subsequent study periods. Hand preference was, however, reinforced in older individuals and an individual's hand preference was stronger in postures with both hands free for foraging. Stable hand preference at an individual level, and its reinforcement over an individual's lifetime, is emerging as a robust finding across the primate order.

Hand preference and Mathematical Learning Difficulties: New data from Greece, the United Kingdom, and Germany and two meta-analyses of the literature

ABSTRACT Increased rates of atypical handedness are observed in neurotypical individuals who are low-performing in mathematical tasks as well as in individuals with special educational needs, such as dyslexia. This is the first investigation of handedness in individuals with Mathematical Learning Difficulties (MLD). We report three new studies (N = 134; N = 1,893; N = 153) and two sets of meta-analyses (22 studies; N = 3,667). No difference in atypical hand preference between MLD and Typically Achieving (TA) individuals was found when handedness was assessed with self-report questionnaires, but weak evidence of a difference was found when writing hand was the handedness criterion in Study 1 (p = .049). Similarly, when combining data meta-analytically, no hand preference differences were detected. We suggest that: (i) potential handedness effects require larger samples, (ii) direction of hand preference is not a sensitive enough measure of handedness in this context, or that (iii) increased rates of atypical hand preference are not associated with MLD. The latter scenario would suggest that handedness is specifically linked to language-related conditions rather than conditions related to cognitive abilities at large. Future studies need to consider hand skill and degree of hand preference in MLD.

An examination of the influence of prenatal sex hormones on handedness: Literature review and amniotic fluid data

Competing theories have posited roles for foetal androgen exposure in the development of human handedness. However, due to practical and ethical considerations, few studies have used hormonal measures to examine this possibility. The current paper reviews this literature and reveals a generally inconsistent pattern of results. We also present data from a longitudinal study of prenatal sex hormone exposure and subsequent handedness. More specifically, we examine correlations between testosterone and estradiol measured from second trimester amniotic fluid and hand preference (Dutch language version of the Edinburgh Handedness Inventory) and hand skill asymmetry (pegboard task) measured at 15 years of age. Prenatal sex hormone exposure was not associated with the direction of hand preference in either males or females. However, in females, high levels of prenatal testosterone were associated with weaker lateralisation of hand skill, and high levels of prenatal estradiol were associated with weaker hand preference. In addition, high levels of prenatal testosterone were associated with increased task duration (i.e., slow hand speed) for the right and left hands of males. The pattern of results observed here is not entirely consistent with any of the main theories linking sex hormones with handedness, suggesting that an association between these variables may be more complex than initially thought.

Hand Preference in Rhinopithecus roxellana Infants: Is It Influenced by Familial Inheritance?

The Sichuan snub-nosed monkey (Rhinopithecus roxellana) is a typical arboreal group-living Old-World primate and has been studied broadly in hand preference. However, infants have not been tested independently from other immature individuals to date. The purpose of the present study was to investigate hand preference in a spontaneously unimanual feeding task in nine infants at 12 months and the relationship of hand preference with their parents in R. roxellanae. Most infants (89%) showed individual-level hand preference. No correlation was found in the direction of hand preference between infant and its parents, and a significant negative correlation in the strength of hand preference was found between infants and their mothers (r = −0.715, p = 0.03). Moreover, there was no sex difference in the direction and strength of hand preference both in infants and adults (i.e., parents). Meanwhile, the strength of hand preference in adults was stronger than that in infants. This study is a first and preliminary exploration for the expression of hand preference in R. roxellanae infants and whether their hand preference was influenced by familial inheritance.

Short and long-term temporal consistency of hand preference in sanctuary chimpanzees (Pan troglodytes) for unimanual and bimanual coordinated tasks

Longitudinal research on manual preferences in humans and non-human primates has mainly been conducted from a developmental perspective, with only a few studies exploring long-term stability of this trait during adulthood. Therefore, we investigated short-term (1 year) and long-term (10 and 11 years) consistency of hand preference in a naturalistic group of 19 juvenile and adult chimpanzees (Pan troglodytes) by using two experimental tasks, one unimanual (simple reaching) and one bimanual (tube task). The experimental sessions were conducted in 2007, 2008 and 2018. We found that the direction of hand preference (right vs. left) in the tube task remained stable after both short-time and long-time periods. Conversely, hand preference direction for simple reaching was not consistent after the longest period (11 years), but the handedness indices (HI) between 2007 and 2008 (1-year period) and between 2008 and 2018 (10-year period) were positively correlated. The comparison between tasks confirmed that all the chimpanzees were more strongly lateralised for the tube task. Interestingly, however, the strength of hand preference in the tube task showed an increasing trend in the long term. We hypothesize that this could be a consequence of practice and experience with a particular motor action.

Beyond frontal alpha: investigating hemispheric asymmetries over the EEG frequency spectrum as a function of sex and handedness

ABSTRACTFrontal alpha EEG asymmetry, an indirect marker of asymmetries in relative frontal brain activity, are widely used in research on lateralization of emotional processing. While most authors focus on frontal electrode pairs (e.g., F3/F4 or F7/F8), several recent studies have indicated that EEG asymmetries can also be observed outside the frontal lobe and in frequency bands other than alpha. Because the focus of most EEG asymmetry research is on the correlations between asymmetry and other traits, much less is known about the distribution of patterns of asymmetry at the population level. To systematically assess these asymmetries in a representative sample, we determined EEG asymmetries across the head in the alpha, beta, delta and theta frequency bands in 235 healthy adults. We found significant asymmetries in all four frequency bands and across several brain areas, indicating that EEG asymmetries are not limited to frontal alpha. Asymmetries were not modulated by sex. They were modulated by direction of hand preference, with stronger right-handedness predicting greater right (relative to left) alpha power, or greater left (relative to right) activity. Taken together, the present results show that EEG asymmetries other than frontal alpha represent markers of asymmetric brain function that should be explored further.

Children’s bilateral advantage for grasp-to-eat actions becomes unimanual by age 10 years

Studies have shown that infants tend to develop a lateralized hand preference for hand-to-mouth actions earlier than they do a preference for many other grasp-to-place or grasp-to-manipulate tasks, years even before direction of hand preference can be reliably determined. This observation has led to a series of studies contrasting the kinematics of grasp-to-eat and grasp-to-place actions in adults. These studies have described a robust kinematic asymmetry between left- and right-handed grasp-to-eat maximum grip apertures (MGAs) that has been interpreted as a right-hand advantage for feeding that may have led to right-handedness as observed on a global scale. The current study examines grasp-to-eat and grasp-to-place kinematics in two groups of typically developing children aged 7 to 12years. It was found that the previously described task difference is present in both hands among younger children and that the effect does not become lateralized until the end of the first decade of life. Additional kinematics of both the dominant and non-dominant hands are described in detail to augment a growing catalogue of reach-to-grasp action descriptions for typically developing children. The maturation of the right-hand advantage for grasp-to-eat actions is discussed in terms of an inherent right-hand/left-hemisphere bias for such actions that may have influenced the development of population-level right-handedness in humans.

Baboons' hand preference resists to spatial factors for a communicative gesture but not for a simple manipulative action

Olive baboons (Papio anubis) do acquire and use intentional requesting gestures in experimental contexts. Individual's hand preference for these gestures is consistent with that observed for typical communicative gestures, but not for manipulative actions. Here, we examine whether the strength of hand preference may also be a good marker of hemispheric specialization for communicative gestures, hence differing from the strength of hand preference for manipulative actions. We compared the consistency of individuals' hand preference with regard to the variation in space of either (i) a communicative partner or (ii) a food item to grasp using a controlled set-up. We report more consistent hand preference for communicative gestures than for grasping actions. Established hand preference in the midline was stronger for gesturing than for grasping and allowed to predict the consistency of hand preference across positions. We found no significant relation between the direction of hand preference and the task.

The Relation between Handedness Indices and Reproductive Success in a Non-Industrial Society

The evolution of handedness in human populations has intrigued scientists for decades. However, whether handedness really affects Darwinian fitness is unclear and not yet studied in a non-industrial society where selection pressures on health and handedness are likely to be similar to the situation in which handedness has evolved. We measured both hand preference and asymmetry of hand skill (speed of fine motor control, measured by a pegboard task, and accuracy of throwing), as they measure different aspects of handedness. We investigated the associations between both the direction (left versus right) and strength (the degree to which a certain preference or asymmetry in skill is manifested, independent of the direction) of handedness. We analyzed to what extent these measures predict the number of offspring and self-reported illness in a non-industrial society in Papua, Indonesia. As it is known that body height and fitness are correlated, data on body height was also collected. Due to low numbers of left-handers we could not investigate the associations between direction of hand preference and measures of Darwinian fitness. We found a positive association between strength of asymmetry of hand skill (pegboard) and the number of children men sired. We also found a positive association for men between strength of hand preference and number of children who died within the first three years of life. For women we found no such effects. Our results may indicate that strength of handedness, independent of direction, has fitness implications and that the persistence of the polymorphism in handedness may be ascribed to either balancing selection on strength of asymmetry of hand skill versus strength of hand preference, or sexual antagonistic selection. No relationships between health and handedness were found, perhaps due to disease related selective disappearance of subjects with a specific handedness.

The sound of one-hand clapping: handedness and perisylvian neural correlates of a communicative gesture in chimpanzees

Whether lateralization of communicative signalling in non-human primates might constitute prerequisites of hemispheric specialization for language is unclear. In the present study, we examined (i) hand preference for a communicative gesture (clapping in 94 captive chimpanzees from two research facilities) and (ii) the in vivo magnetic resonance imaging brain scans of 40 of these individuals. The preferred hand for clapping was defined as the one in the upper position when the two hands came together. Using computer manual tracing of regions of interest, we measured the neuroanatomical asymmetries for the homologues of key language areas, including the inferior frontal gyrus (IFG) and planum temporale (PT). When considering the entire sample, there was a predominance of right-handedness for clapping and the distribution of right- and left-handed individuals did not differ between the two facilities. The direction of hand preference (right- versus left-handed subjects) for clapping explained a significant portion of variability in asymmetries of the PT and IFG. The results are consistent with the view that gestural communication in the common ancestor may have been a precursor of language and its cerebral substrates in modern humans.

Cerebellar asymmetry in a pair of monozygotic handedness‐discordant twins

Increasing evidence for a cerebellar role in human cognition has accrued with respect to anatomically and functionally distinct lobules. Questions of laterality, however, have been largely overlooked. This study therefore introduced and applied a novel measurement protocol for comparatively bias-free analysis of cerebellar asymmetries. Volumetric measurements were performed on magnetic resonance images from a single pair of monozygotic handedness-discordant twins. Against a background of functional cortical asymmetry for verbal and visuo-spatial functional magnetic resonance imaging activation, which was mirrored in the left-handed twin (Lux et al. 2008), between-twin differences in cerebellar asymmetry are described. Interestingly, asymmetry measures for the whole cerebellum did not correspond to either the direction of hand preference or to the weaker (functional magnetic resonance imaging) lateralization of the left-handed twin. The twins both showed clockwise cerebellar torques. This mirrored a counter-clockwise cerebral torque in the right-handed twin only. Selected single cerebellar lobules V and VII displayed between-twin laterality differences that partially reflected their discrepant handedness. Whole cerebellum anatomical measures appeared to be unrelated to single functional cortical asymmetries. These analyses contribute further anatomical evidence pertaining to the existence of multiple structurally and functionally distinct cortico-cerebellar networks of the healthy human brain in vivo.

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preference and performance abilities, a cross-sectional sample of 548 children (ages 3–18) and adults (over 19) completed the Waterloo Handedness Questionnaire, the WatHand Cabinet Test (an observational test of hand preference), and the Annett pegboard. Findings revealed that while the direction of hand preference does not change significantly with age, the degree of hand preference does, such that younger children exhibit weaker hand preference than older children and adults. This pattern of hand preference was much more evident for lefthanded individuals, where consistent hand preference was not seen until 8 years of age. Similarly, performance differences between the hands did not emerge for left-handers until later childhood, while in comparison large performance differences were seen for right-handers at all ages. The implications for the development of handedness will be discussed.

DIRECTION OF HAND PREFERENCE: THE CONNECTION WITH SPEECH AND THE INFLUENCE OF FAMILIAL HANDEDNESS

Taking familial handedness into account, right- and left-handers with differing degrees of hand preference were monaurally presented with verbal stimuli (CVs) to which they responded using their right and left hands at separate times. This reaction time design was used to ascertain the relative cognitive functioning capacity of each hemisphere for verbal processing. However, the results disclosed more about the determination of direction of hand preference than about cognitive processing, per se. It was found that in both strong right-handers and strong left-handers with an incongruent hand preference (i.e., own handedness incongruent with family history of handedness) direction of hand preference is the result of suppression of the nonpreferred hand in the left hemisphere. Strong right- and strong left-handers with a congruent hand preference (i.e., hand preference congruent with family history of handed ness) appear to have a more direct hand preference-left hemisphere mechanism. The findings of the present study are used to form part of a new theory of hand preference determination.

Familial Influences on Hand Preference: Genotypic Variation Between Closely Related Primate Species

The emergence of hemispheric specialization has important implications for the development of higher order cognitive processes, including language and spatial skills. In this research we sought to further understand psychobiological processes associated with the development of hemispheric specialization by examining and comparing familial influences on hand preference in two closely related macaque species: rhesus macaques (Macaca mulatta) and pigtailed macaques (Macaca nemestrina). The results of our study indicate contrasting patterns of familial influence on hand preference in each species. For the rhesus macaque we found a positive correlation in the direction of hand preference between mothers and their juvenile offspring, and for the pigtailed macaque we found a negative mother-offspring correlation in the direction of hand preference. Fathers did not contribute significantly to the direction of hand preference in either species. There was a trend toward a positive correlation for strength and consistency of hand preference between parents and offspring in rhesus macaques but not in pigtailed macaques. These findings indicate that maternal influences on offspring hand preference vary between closely related primate species and lead us to question the generalizability of universal single-factor theories used to explain intergenerational transmission of hand preference in humans.

Familial Influences on Hand Preference: Genotypic Variation Between Closely Related Primate Species

The emergence of hemispheric specialization has important implications for the development of higher order cognitive processes, including language and spatial skills. In this research we sought to further understand psychobiological processes associated with the development of hemispheric specialization by examining and comparing familial influences on hand preference in two closely related macaque species: rhesus macaques (Macaca mulatta) and pigtailed macaques (Macaca nemestrina). The results of our study indicate contrasting patterns of familial influence on hand preference in each species. For the rhesus macaque we found a positive correlation in the direction of hand preference between mothers and their juvenile offspring, and for the pigtailed macaque we found a negative mother-offspring correlation in the direction of hand preference. Fathers did not contribute significantly to the direction of hand preference in either species. There was a trend toward a positive correlation for strength and consistency of hand preference between parents and offspring in rhesus macaques but not in pigtailed macaques. These findings indicate that maternal influences on offspring hand preference vary between closely related primate species and lead us to question the generalizability of universal single-factor theories used to explain intergenerational transmission of hand preference in humans.

Lateral Preferences Among Indian School Children

In the first study, 718 children from India, aged 4 to 11 years, were observed for their hand preference for ten common unimanual activities. The prevalence of left-handedness was found to be only 3.2 percent, i.e. one-third of that (9.6%) observed in a French study using a similar procedure. The degree (weak to strong) but not the direction of hand preference was found to be related to the children's age, with stronger preference among older children. The factor structure of handedness items was similar in France and India. In the second study, 400 schoolchildren from India, aged 6 to 18 years, were examined for handedness, footedness, eyedness, use of hand in space, and absolute and relative hand skill assessed by a peg-moving task and a dot-filling task. Prevalence of left-handedness was 4.2%. A sex difference was observed for handedness, footedness, use of hand in space, and relative hand skill, with higher proportions of right preferences and higher degree of lateralization (i.e., relative between hands asymmetry) in females. The degree of hand skill asymmetry increased with age. These results are discussed in relation to findings from previous studies in other countries using similar procedures.

Left Hand Preferences in Capuchins (Cebus apella): Role of Spatial Demands in Manual Activity

Sixteen capuchins (Cebus apella) participated in four tasks that differed in their exploration demands and availability of visual cues. The two explorative tasks required the monkeys to discover sunflower seeds hidden in crevices in objects of various shapes, with vision (Haptic-Visual task) or without vision (Haptic task). Two other tasks required the capuchins to grasp sunflower seeds directly on a flat support, with vision (Visual reaching) or without vision (Tactual reaching). The presence or absence of exploration demands had a significant effect on the direction of hand preferences. The group displayed greater left hand preferences for the Haptic and Haptic-Visual tasks than for the two reaching tasks. The strength of manual preferences did not differ significantly among the four tasks. These findings suggest that the manipulo-spatial demands of a task are of particular importance for the expression of left hand bias in a population of capuchins. It is argued that left hand preferences for the haptic tasks may reflect a right hemisphere specialisation to integrate the spatial and motor components of action.