Strength Of Hand Preference Research Articles

The evolution and biological correlates of hand preferences in anthropoid primates.

The evolution of human right-handedness has been intensively debated for decades. Manual lateralization patterns in non-human primates have the potential to elucidate evolutionary determinants of human handedness, but restricted species samples and inconsistent methodologies have so far limited comparative phylogenetic studies. By combining original data with published literature reports, we assembled data on hand preferences for standardized object manipulation in 1786 individuals from 38 species of anthropoid primates, including monkeys, apes, and humans. Based on that, we employ quantitative phylogenetic methods to test prevalent hypotheses on the roles of ecology, brain size, and tool use in primate handedness evolution. We confirm that human right-handedness represents an unparalleled extreme among anthropoids and found taxa displaying population-level handedness to be rare. Species-level direction of manual lateralization was largely uniform among non-human primates and did not strongly correlate with any of the selected biological predictors, nor with phylogeny. In contrast, we recovered highly variable patterns of hand preference strength, which show signatures of both ecology and phylogeny. In particular, terrestrial primates tend to display weaker hand preferences than arboreal species. These results challenge popular ideas on primate handedness evolution, including the postural origins hypothesis. Furthermore, they point to a potential adaptive benefit of disparate lateralization strength in primates, a measure of hand preference that has often been overlooked in the past. Finally, our data show that human lateralization patterns do not align with trends found among other anthropoids, suggesting that unique selective pressures gave rise to the unusual hand preferences of our species.

Age, but not hand preference, is related to personality traits in common marmosets (Callithrix jacchus).

The proximate mechanisms underlying animal personalities, i.e. consistent inter-individual differences in behaviour, are a matter of discussion. Brain lateralization, expressed as the preferred use of the contralateral limb, has been suggested as one of these mechanisms. In this study, we measured a proxy of brain lateralization in captive common marmosets (N = 28) by testing hand preference in a simple food-reaching task and evaluated personality by coding a wide range of behaviours observed in daily situations. We explored the links between personality and both direction and strength of hand preference, as well as age and sex, using linear models. Principal component analysis revealed that the stable behavioural variables were organized in three personality dimensions: Agreeableness, Extraversion and Neuroticism. Regarding hand preference, 14 individuals were left-handed, seven were right-handed and seven were ambilateral. Contrary to our predictions, we did not find any relationship between personality scores and hand preference or sex. Instead, age was a significant predictor of personality scores, with older individuals being more agreeable and less extraverted. The link between brain lateralization and personality seems to be equivocal and dependent on personality and brain lateralization assessment methods. Further examinations of other proximate mechanisms, such as physiology or (epi)genetics, may elucidate what drives personality variation in common marmosets.

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.

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.

Differential Ageing of the Brain Hemispheres: Evidence from a Longitudinal Study of Hand Preferences in Common Marmosets

This paper is concerned with decreasing asymmetry of motor control in ageing. It discusses age-related changes in humans and reports a longitudinal study of hand preferences in common marmosets. An annual assessment of hand preference for holding food was recorded throughout the lifespan of 19 marmosets that lived for at least 9 years, and half of those lived for at least 11 years. Those with a left-hand preference showed a gradual reduction in the strength of their hand preference throughout adult life. No significant change in the strength of hand preference was found in right-handed marmosets. Hence, ageing has a specific effect on motor control by the right hemisphere.

Between-task consistency, temporal stability and the role of posture in simple reach and fishing hand preference in chimpanzees (Pan troglodytes)

Studying hand preferences in chimpanzees can provide insights into the evolutionary origins of human hemispheric specialization. Research on chimpanzee hand preference requires careful examination of important factors such as between-task consistency, temporal stability and posture although few studies have investigated all of these factors in combination. We investigated hand preference in simple reach and fishing behaviours in a group of 19 chimpanzees at Chester Zoo in the UK. Simple reach was defined as extending a hand to grasp a small object, then flexing the limb in a continuous motion, and was examined in quadrupedal, sitting and climbing postures. Fish in hole was defined as inserting a stick into a hole in the wall with one hand and then extracting it with the same hand. Between-task consistency of hand preference was assessed by comparing simple reach and fish in hole, while temporal stability was assessed by comparing simple reach from two points in time: 2017 and 2019. The data showed no significant influence of posture on the strength of hand preference, which contrasts with previous research. The findings of this study show temporal stability in simple reach, although only partial between-task consistency. Overall, the results indicate that simple reach elicits laterality at the individual level and is consistent across postures and stable over time, which is consistent with the literature. These results suggest that posture stability may be important in affecting hand preference. Further, whilst there was overall stability in hand preference across time periods, some individuals changed their preferred hand, suggesting there may be individual-level temporal instability of hand preference for certain tasks.

Hand preference for a bimanual coordinated task in captive hatinh langurs (Trachypithecus hatinhensis) and grey-shanked douc langurs (Pygathrix cinerea)

Right-handedness in humans reflects the functional brain specialisation of the left hemisphere. To better understand the origins of this population-level tendency, it is crucial to understand manual lateralisation in other non-human primate species. The aim of this article is to present a first approach to the hand preference of two primates from Vietnam, the endangered hatinh langur (Trachypithecus hatinhensis) and the critically endangered grey-shanked douc langur (Pygathrix cinerea). Eighteen individuals from each species (N = 36) were evaluated by means of the bimanual coordinated tube task and their responses were recorded in terms of manual events and bouts. Our results showed that subjects presented strong individual-level preferences but not lateralisation at the group-level. No sex differences were detected within species. The index finger was used in all of the extractions during this bimanual task, alone (86 %) or in combination with other fingers (14 %). In addition, hatinh langurs exhibited a greater strength of hand preferences than grey-shanked douc langurs, pointing to a possible higher manual specialisation during the leaf-eating process. These findings help to broaden our scarce knowledge of manual laterality in Asian colobine monkeys and confirm the bimanual tube task as a sensitive measure for assessing manual laterality in non-human primates.

The Influence of Target Animacy and Social Rank on Hand Preference in Barbary Macaques (Macaca sylvanus)

Brain hemispheres have different functions and control the movements of the contralateral side of the body. One of these functions is processing emotions. The right hemisphere hypothesis suggests that the right hemisphere of the brain is responsible for emotional processing, so the left side of the body is activated in emotive contexts such as social interactions. In contrast, the valence hypothesis proposes that both hemispheres are involved in emotional processing, with the left hemisphere processing positive emotions and the right hemisphere negative emotions. We investigated whether and how interaction with inanimate and animate targets affected manual laterality in 12 zoo-housed Barbary macaques (Macaca sylvanus). We focused on the direction and the strength of hand preference and tested the effect of social rank on lateralization. We used continuous focal animal sampling to record bouts of hand preference when interacting with inanimate targets (fourteen 15-min samples) and animate targets (during social and self-directed behaviors, fourteen 2-h morning samples and 14 90-min afternoon samples) and recorded social interactions to measure rank. At the individual level, six of nine lateralized macaques were significantly right-handed when interacting with inanimate targets, whereas only three subjects showed a significant (right) lateralization when interacting with animate targets. Thus, inanimate targets seem to elicit manual laterality to a greater extent than animate targets. At the group level, we found no hand preference for actions directed toward inanimate or animate targets in general but we found a right-hand bias for affiliative behaviors. There was no effect of social rank on lateralization. Despite the limitations of a small sample size, our results suggest that both hemispheres influence hand preference during social interactions, supporting the valence hypothesis.

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.

Personality and lateralization in common marmosets (Callithrix jacchus)

Specialization of the left and right hemispheres to control behavioural responses may represent one of the mechanisms underlying individual differences in personality structure, as well as the preferential use of one hand. The present study investigated the relationship between personality and hand preference in common marmosets (Callithrix jacchus), a little New World monkey that presents highly consistent and stable individual hand preferences for simple reaching. To address this issue, data on 56 different behaviours from the species’ behavioural repertoire were measured in 10 different laboratory tests and during observations under social conditions on 16 adult common marmosets. Stable behavioural variables were aggregated a priori into 13 personality traits. Exploratory Factor Analysis (EFA) on personality traits was carried out to verify the presence of major personality factors, and their relationship with direction and strength of individual hand preferences was assessed by multiple regression, taking into account sex and age of the subjects. The largest number of species-specific behaviours so far investigated in this species was taken into account and robust temporal stability between two testing periods was verified. We confirm that common marmosets are characterized by specific and stable personality profiles. A single personality factor, accounting for about 38% of the total variance, was found by EFA, that describes the interest towards unusual and new experiences and resembles the human Openness domain. The strength of the hand preference was found to be predicted by this personality factor, that we named Inquisitiveness. Present results highlight common marmoset as a useful primate model for the study of the relationship between personality and lateralization.

Stage 2 Registered Report: There is no appreciable relationship between strength of hand preference and language ability in 6- to 7-year-old children

Background: Weak or inconsistent hand preference has been postulated to be a risk factor for developmental language delay. Following on from our Registered Stage 1 report this study assessed the extent to which variations in language skills are associated with the strength of hand preference. Methods: Data are drawn from a large sample ( N = 569) of 6- to 7-year-old children unselected for ability, assessed at two time points, 6 months apart. Hand preference was assessed using the Quantitative Hand Preference (QHP) task and five uni-manual motor tasks. Language skills (expressive and receptive vocabulary, receptive grammar, and morphological awareness) were assessed with standardized measures. Results: We found QHP scores did not distinguish children with weaker language skills from those with stronger language skills and the correlation between QHP scores and language ability was negligible in this study. Hand preference on the QHP task was significantly stronger among right-handed than left-handed children and left-handed children were typically inconsistent in the hand used across different tasks. Conclusions: The findings presented here fail to provide any support for the theory that weak cerebral lateralisation (as assessed here by the QHP task) places children at risk of language difficulties . Stage 1 report: https://doi.org/10.12688/wellcomeopenres.15077.1

Stage 2 Registered Report: There is no appreciable relationship between strength of hand preference and language ability in 6- to 7-year-old children.

Background: Weak or inconsistent hand preference has been postulated to be a risk factor for developmental language delay. Following on from our Registered Stage 1 report this study assessed the extent to which variations in language skills are associated with the strength of hand preference. Methods: Data are drawn from a large sample ( N = 569) of 6- to 7-year-old children unselected for ability, assessed at two time points, 6 months apart. Hand preference was assessed using the Quantitative Hand Preference (QHP) task and five uni-manual motor tasks. Language skills (expressive and receptive vocabulary, receptive grammar, and morphological awareness) were assessed with standardized measures. Results: We found QHP scores did not distinguish children with weaker language skills from those with stronger language skills and the correlation between QHP scores and language ability was negligible in this study. Hand preference on the QHP task was significantly stronger among right-handed than left-handed children and left-handed children were typically inconsistent in the hand used across different tasks. Conclusions: The findings presented here fail to provide any support for the theory that weak cerebral lateralisation (as assessed here by the QHP task) places children at risk of language difficulties . Stage 1 report: https://doi.org/10.12688/wellcomeopenres.15077.1.

Preferential hand use by captive chimpanzees (Pan troglodytes) in manual and tool digging

Digging for underground storage organs of plants has been reported in various populations of wild chimpanzees (Pan troglodytes). However, it is unknown so far whether chimpanzees display lateral biases in manual digging as direct observations of this behavior are still lacking. It was therefore the aim of the present study to assess, for the first time, hand preferences for digging in a group of nine captive chimpanzees. We found that with only one exception, all individuals engaged in manual digging for buried food. Five individuals displayed a significant right-hand preference, two a significant left-hand preference, and one was ambidextrous. No apparent differences between males and females were found with regard to the direction or strength of hand preferences for manual digging. Only one out of four parent–offspring pairs was congruent in their preferred hand for manual digging. Three of the eight chimpanzees who dug manually also used tools in order to excavate buried food. Among those three individuals, one displayed a significant right-, one a significant left-hand preference, and one was ambidextrous. Only one of these three chimpanzees was consistent in preferring the same hand for manual and tool digging. The present findings are in line with the notion that chimpanzees display significant hand preferences at the individual level for haptic-guided behaviors, with a tendency for the right hand.

Stage 1 Registered Report: The relationship between handedness and language ability in children

Weak or inconsistent hand preference may be a risk factor for developmental language delay. This study will test the extent to which variations in language skills are associated with the strength of hand preference. Data are drawn from a large sample (n = 569) of 6- to 7-year-old children unselected for ability, assessed at two time points, 6 months apart. Hand preference is assessed using the Quantitative Hand Preference task (QHP) and five uni-manual motor tasks. Language skills (expressive and receptive vocabulary, receptive grammar, and morphological awareness) are assessed with standardized measures. If weak cerebral lateralisation (as assessed by the QHP task) is a risk factor for language difficulties, it should be possible to detect such effects in the large representative sample of children examined here.

Stage 1 Registered Report: The relationship between handedness and language ability in children.

Weak or inconsistent hand preference may be a risk factor for developmental language delay. This study will test the extent to which variations in language skills are associated with the strength of hand preference. Data are drawn from a large sample (n = 569) of 6- to 7-year-old children unselected for ability, assessed at two time points, 6 months apart. Hand preference is assessed using the Quantitative Hand Preference task (QHP) and five uni-manual motor tasks. Language skills (expressive and receptive vocabulary, receptive grammar, and morphological awareness) are assessed with standardized measures. If weak cerebral lateralisation (as assessed by the QHP task) is a risk factor for language difficulties, it should be possible to detect such effects in the large representative sample of children examined here.

Effects of age, sex and manual task on hand preference in wild Rhinopithecus roxellana.

Golden snub-nosed monkeys (Rhinopithecus roxellana), as typical arboreal group-living Old World monkeys, provide an appropriate animal model to research manual laterality and explore the factors affecting hand preference in non-human primates (NHP). This study investigated hand preference based on 63 subjects and four spontaneous manual tasks (including unimanual and bimanual feeding and grooming), and assessed the effects of age, gender and type of task on handedness in R. roxellana. A population-level left-handedness was found not only in the bimanual coordinated tasks (bimanual feeding and grooming), but also in one unimanual reaching task (unimanual feeding). There were no significant differences between the sexes in either direction or strength of hand preference among any task. However, a significant difference between adults and juveniles was found in the unimanual feeding task. This is the first report on handedness in unimanual and bimanual feeding tasks that require bipedal posture in wild R. roxellana. Furthermore, this study demonstrated spontaneous feeding tasks reported previously only in the quadrupedal posture in this species, supporting the importance of factors such as posture and task complexity in the evolution of primate manual lateralization.

Hand preferences in two unimanual and two bimanual coordinated tasks in the black-handed spider monkey (Ateles geoffroyi).

Spider monkeys are interesting to study with regard to hand preferences, as they are one of the few primate species that lack a thumb and, thus, are unable to perform a precision grip. Further, being platyrrhine primates, they also largely lack independent motor control of the digits and, thus, have only limited manual dexterity. It was therefore the aim of the present study to assess hand preferences in black-handed spider monkeys (Ateles geoffroyi) in 4 tasks differing in task demand: simple unimanual reaching for food and 3 versions of the widely used tube task, including 2 bimanual versions that differ from each other in the degree of fine motor control needed and a unimanual version that does not require coordinated action of the hands. We found that black-handed spider monkeys display significant hand preferences at the individual, but not at the population, level. This was true both in the 2 bimanual coordinated tasks and in the 2 unimanual tasks. Further, our results show that the majority of animals were consistent in the hand they preferred in these 4 tasks. Our findings only partially support the notion that task demand positively correlates with strength of hand preference. Finally, we found that the index finger was the most frequently used digit in all 3 tube tasks, although the animals also used other digits and 2- and 3-finger combinations to extract food from a tube. We conclude that limited manual dexterity does not prevent spider monkeys from displaying strong and consistent hand preferences at the individual level. (PsycINFO Database Record

Manual bias, behavior, and cognition in common marmosets and other primates.

This chapter examines the importance of studying hand preference together with different expressions of behavior. Cognitive differences between left- and right-handed primates are discussed. As shown in several species of primate, eye preference, but not hand preference, is biased at the level of the population and reflects hemispheric asymmetry of processing. Hand preference, determined from simple grasping of pieces of food and taking them to the mouth, is consistent for individuals but it is not population biased. It is a measure of an individual's preference to use a particular hemisphere, and hence which cognitive processes are characteristic of the individual. Compared to left-handed subjects, right-handed subjects are more active in exploring novel objects, show more social facilitation of behavior, have a positive cognitive bias, and express lower levels of fear and stress responses. In marmosets, learning of food searching tasks is not associated with hand preference. Strength of hand preference, rather than its direction, is linked to the ability to perform two tasks at once, viz., detection of a predator while searching for food. Marmosets with strong hand preferences are able to perform these two tasks at once but those with weak or no hand preference are unable to do so.

Preliminary study on hand preference in captive northern white-cheeked gibbons (Nomascus leucogenys).

The postural origin hypothesis and the task complexity hypothesis propose that hand preference in non-human primates evolved in association with body posture and task complexity, respectively. The results of previous studies testing these two hypotheses, however, vary greatly with the different primate species and methods used. To investigate the effect of body posture and task complexity on hand preference, we recorded bouts of hand usage in nine captive northern white-cheeked gibbons (Nomascus leucogenys) housed at Beijing Zoo as they reached for food items in a ground-reaching task, a box task, and a tube task. The results showed that four to seven of the nine gibbons displayed a hand preference at the individual level in different tasks, and that hand preference in individuals was task-specific; there was no group-level hand preference in any task. The box task seemed to elicit a greater strength of hand preference than the ground-reaching task at the individual level. Although the small sample size rules out drawing any strong conclusions concerning hand preference at the group level, our results suggest that the suspensory reaching posture might increase the expression of hand preference at the individual level. This study provides preliminary information on hand preference in captive northern white-cheeked gibbons, and will be helpful for future studies addressing the origin and evolution of hand preference in small apes.