Strength Of Handedness Research Articles

A Dynamic Model of Human Limb Selection

Two experiments and a dynamic model forhuman limb selection are reported. In Experiment 1, left-handed and right-handed participants (N = 36) repeatedly used one hand for grasping a small cube. After a clear switch in the cube’s location, perseverative limb selection was revealed in both handedness groups. In Experiment 2, the cubes were presented in a clockwise and counter-clockwise sequence to right-handed participants (N = 15). A spatial shift in the switch point between right-hand use and left-hand use was observed. The model simulates the experiments by implementing the nonlinear multiple-timescale dynamics of the action-selection process underlying limb selection. It integrates two mechanisms that were earlier proposed to underlie this selection aspect of manual activity: limb dominance and attentional information. Finally, the model is used to simulate an influential earlier experiment, by establishing a conceptual link between cross-lateral inhibition asymmetry and the direction and strength of handedness.

Handedness in ADHD: Meta-Analyses.

Meta-analyses have shown that several neurodevelopmental and psychiatric disorders, such as autism spectrum disorder and schizophrenia, are associated with a higher prevalence of atypical (left-, non-right-, or mixed-) handedness. One neurodevelopmental disorder for which this association is unclear is attention deficit hyperactivity disorder (ADHD). Here, some empirical studies have found evidence for a higher prevalence of atypical handedness in individuals with ADHD compared to neurotypical individuals. However, other studies failed to establish such an association. Therefore, meta-analytic integration is critical to estimate whether or not there is an association between handedness and ADHD. We report the results of three meta-analyses (left-, mixed-, and non-right-handedness) comparing handedness in individuals with ADHD to controls (typically developing individuals). The results show evidence of a trend towards elevated levels of atypical handedness when it comes to differences in left- and mixed-handedness (p = 0.09 and p = 0.07, respectively), but do show clear evidence of elevated levels of non-right-handedness between individuals with ADHD and controls (p = 0.02). These findings are discussed in the context of the hypothesis that ADHD is a disorder in which mostly right-hemispheric brain networks are affected. Since right-handedness represents a dominance of the left motor cortex for fine motor behavior, such as writing, as well as a left-hemispheric dominance for language functions, and about 90% of individuals are right-handers, this hypothesis might explain why there is not stronger evidence for an association of left-handedness with ADHD. We suggest that the mechanisms involved in the pathogenesis of ADHD might show an overlap with the mechanisms involved in handedness strength, but not handedness direction.

Investigating the Efficacy of the Hand Selection Complexity Task Across the Lifespan

There is inconsistent evidence demonstrating a relationship between task complexity and hand preference. However, analyzing the point at which task complexity overrides the decision to demonstrate a biomechanically efficient movement can enable complexity to be quantified. Young children (ages 3–7), adolescents (ages 8–12), young adults (ages 18–25), and older adults (ages 65+) performed a newly developed Hand Selection Complexity Task (HSCT) and completed the Waterloo Handedness Questionnaire (WHQ). The HSCT included a reciprocal Fitts’ tapping task performed in the contralateral space (i.e., same side as preferred hand), followed by ipsilateral space (i.e., opposite side of preferred hand). An alternating contralateral-ipsilateral pattern enabled the participant to progress through six levels of difficulty in three conditions (manipulating target amplitude, width, and combined factors). As participants were free to perform with whichever hand (i.e., preferred, non-preferred) they deemed most appropriate, the level of difficulty where a hand switch occurred was identified. HSCT completion time and error scores were also computed. Findings revealed age to be a significant predictor of dependent measures when considering significant effects and interactions. Combined with the covariate WHQ score as a significant predictor of HSCT time and errors (in some, but not all cases), it can be argued that age-related effects reflect the development of handedness, and changes in strength of handedness across the lifespan. Together, findings suggest that task complexity plays an important role in hand selection when performing a task of increasing difficulty. It appears that task complexity will take precedent over object proximity and biomechanical efficiency, at a certain point, in order to complete the movement with the preferred hand. This point ultimately changes throughout the lifespan.

The SETDB2 locus: evidence for a genetic link between handedness and atopic disease.

The gene SETDB2, which mediates aspects of laterality in animal model systems, has recently been linked with human handedness as measured continuously on a scale from strong left to strong right. By contrast, it was marginally associated with a left-right dichotomous measure, and it showed no evidence of association with absolute handedness strength independent of direction. We genotyped the SETDB2 handedness-associated single nucleotide polymorphism, rs4942830, in a large healthy population likewise phenotyped for continuous, absolute, and dichotomous handedness variables. Our results demonstrated significant effects of rs4942830 genotype on continuous handedness, and weaker, marginal effects on dichotomous handedness, but no effects on absolute handedness. These results help to establish the locus marked by the SNP rs4942830 as a strong candidate for mediating human handedness. Intriguingly, rs4942830 is also in complete linkage disequilibrium with rs386770867, a polymorphism recently shown to affect human serum levels of IgE production and other atopic phenotypes. These findings implicate this locus in the longstanding links of handedness with asthma and other atopic diseases.

Segregating polymorphisms of FOXP2 are associated with measures of inner speech, speech fluency and strength of handedness in a healthy population

We genotyped a healthy population for three haplotype-tagging FOXP2 SNPs, and tested for associations of these SNPs with strength of handedness and questionnaire-based metrics of inner speech characteristics (ISP) and speech fluency (FLU), as derived from the Schizotypal Personality Questionnaire-BR. Levels of mixed-handedness were positively correlated with ISP and FLU, supporting prior work on these two domains. Genotype for rs7799109, a SNP previously linked with lateralization of left frontal regions underlying language, was associated with degree of mixed handedness and with scores for ISP and FLU phenotypes. Genotype of rs1456031, which has previously been linked with auditory hallucinations, was also associated with ISP phenotypes. These results provide evidence that FOXP2 SNPs influence aspects of human inner speech and fluency that are related to lateralized phenotypes, and suggest that the evolution of human language, as mediated by the adaptive evolution of FOXP2, involved features of inner speech.

Handedness and social anxiety: Using Bryden's research as a catalyst to explore the influence of familial sinistrality and degree of handedness

ABSTRACTPhil Bryden's work has impacted on many areas of laterality, including degree and measurement of hand preference, as well as influences of familial sinistrality (FS). For example, Bryden[(1977). Measuring handedness with questionnaires. Neuropsychologia, 15, 617–624] is a well-cited and influential paper that remains relevant to this day. Inspired by this we extended our analysis of the relationship between handedness and anxiety in a number of ways. We used familial handedness and strength of handedness to examine their potential influences on anxiety, and extended our research by exploring their relationship to social anxiety, using the Social Phobia Inventory (SPIN). Inconsistent left-handers (ILH) were found to be more socially anxious. In all categories of SPIN except avoidance, ILH were significantly more anxious than consistent right- and left-handers. There were FS differences between ILH with a first degree left-handed relative (FS+) compared to ILH with no first degree left-handed relative (FS−) on all categories of anxiety scores. Within FS+ participants, ILH had significantly higher anxiety scores, compared with consistent handers across all categories. This suggests that ILH's social anxiety may be influenced by a close left-handed relative. Inspired by examining Bryden's work for this special issue, we will continue to add both strength of preference and familial handedness to our work.

Neurostructural correlates of consistent and weak handedness

ABSTRACTVarious cognitive differences have been reported between consistent and weak handers, but little is known about the neurobiological factors that may be associated with this distinction. The current study examined cortical structural lateralization and corpus callosum volume in a large, well-matched sample of young adults (N = 164) to explore potential neurostructural bases for this hand group difference. The groups did not differ in corpus callosum volume. However, at the global hemispheric level, weak handers had reduced or absent asymmetries for grey and white matter volume, cortical surface area, thickness, and local gyrification, relative to consistent handers. Group differences were also observed for some regional hemispheric asymmetries, the most prominent of which was reduced or absent gyrification asymmetry for weak handers in a large region surrounding the central sulcus and extending into parietal association cortex. The findings imply that variations in handedness strength are associated with differences in structural lateralization, not only in somatomotor regions, but also in areas associated with high level cognitive control of action.

Responding to framed health messages: Different strokes for different (handedness) folks

Research has shown that strength of handedness – a proxy variable for the degree of interaction between the left and right brain hemispheres – predicts differences in a variety of cognitive domains. The present paper extends this work to message (or goal) framing effects in which persuasive health communications emphasise positive vs. negative outcomes. One hundred fifty-six participants read pamphlets containing statements emphasising either the gains of using or the losses of not using sunscreen. Replicating previous research, non-users of sunscreen were more affected by framed messages than users. However, we found a loss- rather than gain-framed advantage, and mixed (inconsistent)-handers seemed to drive these effects more so than strong (consistent)-handers. These results suggest that a ‘one-size-fits-all’ approach may be inadequate in crafting effective educational messages about health behaviours, and that theories centring around one’s regulatory focus orientation as well as new methods in laterality research may be useful in reaching the widest range of individuals.

“All‐or‐None” Versus “Most‐or‐Some” Options in Risky Choice: Effects of Domain and Handedness

ABSTRACTTwo methodological variants of Kahneman and Tversky's Asian disease scenario were investigated. One variant involved replacing the “all‐or‐none” outcome scenarios of the risky choice with “most‐or‐some” scenario outcomes, and the second variant involved replacing the negative domain of lives lost with a positive domain of jobs created. In addition, the effects of strength of handedness, a variable related to individual differences in risk perception, were examined. Results indicated that standard framing effects were obtained across both domains, with a decrease in risky choice under the gain domain. Scenario type also interacted with handedness, such that the all‐or‐none scenario yielded framing effects for consistent (strong)‐handers only, whereas the most‐or‐some scenario yielded framing effects for inconsistent (mixed)‐handers only (consistent‐handers are those who use the same hand exclusively for almost all activities). These results demonstrate that framing effects are strongly influenced by the presence versus absence of extreme/absolute outcomes and that individuals (in this case, decision makers with varying degrees of handedness strength) are differentially sensitive to different pieces of information. Copyright © 2014 John Wiley & Sons, Ltd.

Handedness differences in information framing

Previous research has shown that strength of handedness predicts differences in sensory illusions, Stroop interference, episodic memory, and beliefs about body image. Recent evidence also suggests handedness differences in the susceptibility to common decision biases such as anchoring and sunk cost. The present paper extends this line of work to attribute framing effects. Sixty-three undergraduates were asked to advise a friend concerning the use of a safe allergy medication during pregnancy. A third of the participants received negatively-framed information concerning the fetal risk of the drug (1–3% chance of having a malformed child); another third received positively-framed information (97–99% chance of having a normal child); and the final third received no counseling information and served as the control. Results indicated that, as predicted, inconsistent (mixed)-handers were more responsive than consistent (strong)-handers to information changes and readily update their beliefs. Although not significant, the data also suggested that only inconsistent handers were affected by information framing. Theoretical implications as well as ongoing work in holistic versus analytic processing, contextual sensitivity, and brain asymmetry will be discussed.

Genetic and environmental contributions to the expression of handedness in chimpanzees (Pan troglodytes).

Most humans are right-handed and, like many behavioral traits, there is good evidence that genetic factors play a role in handedness. Many researchers have argued that non-human animal limb or hand preferences are not under genetic control but instead are determined by random, non-genetic factors. We used quantitative genetic analyses to estimate the genetic and environmental contributions to three measures of chimpanzee handedness. Results revealed significant population-level handedness for two of the three measures-the tube task and manual gestures. Furthermore, significant additive genetic effects for the direction and strength of handedness were found for all three measures, with some modulation due to early social rearing experiences. These findings challenge historical and contemporary views of the mechanisms underlying handedness in non-human animals.

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.

How are autism and schizotypy related? Evidence from a non-clinical population.

Both autism spectrum conditions (ASCs) and schizophrenia spectrum conditions (SSCs) involve altered or impaired social and communicative functioning, but whether these shared features indicate overlapping or different etiological factors is unknown. We outline three hypotheses (overlapping, independent, and diametric) for the possible relationship between ASCs and SSCs, and compare their predictions for the expected relationships between autistic and schizotypal phenotypes using the Autism Spectrum Quotient and the Schizotypal Personality Questionnaire-Brief Revised from a large non-clinical sample of undergraduate students. Consistent with previous research, autistic features were positively associated with several schizotypal features, with the most overlap occurring between interpersonal schizotypy and autistic social and communication phenotypes. The first component of a principal components analysis (PCA) of subscale scores reflected these positive correlations, and suggested the presence of an axis (PC1) representing general social interest and aptitude. By contrast, the second principal component (PC2) exhibited a pattern of positive and negative loadings indicative of an axis from autism to positive schizotypy, such that positive schizotypal features loaded in the opposite direction to core autistic features. These overall PCA patterns were replicated in a second data set from a Japanese population. To evaluate the validity of our interpretation of the PCA results, we measured handedness and mental rotation ability, as these are established correlates of SSCs and ASCs, respectively. PC2 scores were significantly associated with hand preference, such that increasingly ‘schizotypal’ scores predicted reduced strength of handedness, which is consistent with previous research. PC1 scores were positively related to performance on the mental rotation task, suggesting trade-offs between social skills and visual-spatial ability. These results provide novel evidence for an autism-positive schizotypy axis, and highlight the importance of recognizing that psychological variation involving reduced social interest and functioning may have diverse causes.

The relationship between Revised Reinforcement Sensitivity Theory (rRST), handedness and indecision

Indecisiveness is an inability to make a decision, manifest across a number of behaviours. We explore the influence that both direction and strength of hand preference may have on this construct, examining it in relation to the revised Reinforcement Sensitivity Theory (rRST). Frost and Shows’ (1993) Indecisiveness Scale was administered to 328 undergraduates (221 females), alongside the Edinburgh Handedness Inventory (Oldfield, 1971) and Carver and White’s (1994) BIS/BAS scales. Simple correlations showed left-handers had a positive relationship between strength of handedness and BIS. In right-handers, strength and aversive indecision were positively correlated. Regression analysis demonstrated no significant relationship between hand strength and indecision, but that indecision was related to all three measures of rRST. Consistent with previous work, BIS was positively related to all indecision but particularly aversive, while BAS was negatively related to indecision but most strongly the avoidant category. We found that FFFS is more closely related to aversive than avoidant indecision. The relationship between rRST and indecision may be influenced by handedness; for right-handers the same pattern was found, but in left-handers BAS was not a significant predictor of indecision, BIS only predicted aversive indecision and FFFS predicted all three categories.

Strength, But Not Direction, of Handedness Is Related to Height

Left-handers are reputed to be shorter than right-handers. However, previous research has confounded handedness direction (left-versus right-handedness) with handedness strength (consistency with which one hand is chosen across a variety of tasks; consistent-versus inconsistent-handedness). Here, we support a relationship between handedness strength, but not direction, and stature, with increasing inconsistent-handedness associated with increasing self-reported height.

Degree of handedness, emotion, and the perceived duration of auditory stimuli

Humans exhibit a remarkable ability to accurately judge time intervals, but this ability varies among individuals and across situations. Research suggests that arousal and attentional factors are consistently associated with subjective time distortions, and emotions such as anger, which can elicit arousal and attract attention, have frequently been studied in this context. Typically, viewing angry faces seems to consistently produce time overestimation relative to neutral faces, and the present study investigates the possibility that this effect extends to angry voices by means of a temporal bisection task. Additionally, this paper furthers previous findings that interhemispheric interaction as quantified by handedness strength (i.e., the degree to which one favours one hand over the other) is related to how individuals perceive future time points on an imagined time task, and explores the possibility that handedness strength differences may also manifest as differences in bisection task performance. Results showed that handedness strength was associated with differences in time perception in both objective (bisection) and subjective (imagined) contexts. Bisection task data further revealed that the angry stimulus was associated with decreased temporal sensitivity and a greater propensity to categorise stimuli as “short” as compared to the same stimulus spoken in a neutral voice, which contrasts with studies conducted using angry faces. Possible attentional explanations for these findings and suggestions for future research directions are discussed.

Relation between comparative risk, absolute risk, and worry: The role of handedness strength

Research is mixed regarding whether comparative or absolute risk perceptions are most associated with important outcomes (e.g. worry). The current research examined the role of individual differences in organizational brain structure and connectivity-assessed via handedness strength-in moderating these effects. Strong handers and mixed handers made comparative and absolute risk estimates for contracting a sexually transmitted disease or sexually transmitted infection and also indicated their worry. Additionally, participants indicated whether they received testing for sexually transmitted diseases or sexually transmitted infections. For strong handers, absolute risk perceptions were generally more associated with worry and testing behaviors, whereas for mixed handers, comparative risk perceptions were more associated.

Handed Foraging Behavior in Scale-Eating Cichlid Fish: Its Potential Role in Shaping Morphological Asymmetry

Scale-eating cichlid fish, Perissodus microlepis, from Lake Tanganyika display handed (lateralized) foraging behavior, where an asymmetric ‘left’ mouth morph preferentially feeds on the scales of the right side of its victim fish and a ‘right’ morph bites the scales of the left side. This species has therefore become a textbook example of the astonishing degree of ecological specialization and negative frequency-dependent selection. We investigated the strength of handedness of foraging behavior as well as its interaction with morphological mouth laterality in P. microlepis. In wild-caught adult fish we found that mouth laterality is, as expected, a strong predictor of their preferred attack orientation. Also laboratory-reared juvenile fish exhibited a strong laterality in behavioral preference to feed on scales, even at an early age, although the initial level of mouth asymmetry appeared to be small. This suggests that pronounced mouth asymmetry is not a prerequisite for handed foraging behavior in juvenile scale-eating cichlid fish and might suggest that behavioral preference to attack a particular side of the prey plays a role in facilitating morphological asymmetry of this species.

Inaction inertia, the sunk cost effect, and handedness: Avoiding the losses of past decisions

Strength of handedness, or the degree to which an individual prefers to use a single hand to perform various tasks, is a neurological marker for brain organization and has been shown to be linked to episodic memory, attribute framing, and anchoring, as well as other domains and tasks. The present work explores the relationship of handedness to both inaction inertia (the inclination to resist an action after previously bypassing a similar action) as well as to the sunk cost effect (the tendency to continue to engage in a behavior after an initial investment of time or money has been made). In Experiment 1, mixed-handers displayed a larger inaction inertia effect than strong-handers. In Experiment 2, they displayed a larger sunk cost effect than strong-handers. Experiments 3 and 4 extended the sunk cost finding into a different domain and explored how mixed- and strong-handers react to additional information designed to increase the comparative advantage of terminating, rather than continuing, a failed project. Overall, we found that mixed-handers were more likely to show inertia effects because of an increased aversion to losses. The results of Experiment 4 suggest that, when provided with additional information that made it clear that continuing a project would be a greater loss than terminating it, mixed-handers no longer showed a larger sunk cost effect than strong-handers, highlighting the importance of carefully considering exactly how sunk cost scenarios are worded and providing additional information on how mixed- and strong-handers differ in belief updating.

Handedness and ‘open-earedness’: Strong right-handers are less likely to prefer less popular musical genres

Research shows that strong right-handedness is associated with decreased cognitive flexibility and decreased tendencies to update beliefs, arising from decreased interhemispheric interaction. In the current study, strong right-handedness was associated with decreased overall liking of less popular musical genres (with the specific genres of bluegrass and reggae attaining significance) and marginally increased preference for more popular genres (with popularity being indexed by recording industry sales figures), providing further evidence for decreased cognitive flexibility in strong right-handers and suggesting that strength of handedness is an important factor in individual differences in musical preferences.