A meta-analysis is reported of 88 studies, examining 100 study populations, in which the handedness of 284665 individuals has been assessed. The overall incidence of left-handedness was 7.78%. The incidence of left-handedness was not related to the method of measurement, or the length or number of response items included in inventories. Study populations with lower response rates and smaller study populations showed some evidence of higher incidences of left-handedness, presumably due to response biasses. There was no evidence that the incidence of left-handedness was related to the year of publication of studies; however the incidence of left-handedness was lower in older subjects and in those from earlier birth cohorts, the two effects not being statistically distinguishable.Information was available from 64 study populations concerning the incidence of left-handedness in males and females; overall 8.52% of males were left-handed compared with 6.69% of females, the male incidence being 27.4% higher than that in females. Although there was some suggestion that the sex difference was greater in larger studies, and in studies whose main purpose was not the study of handedness, these differences were not significant. It is concluded that the size of the sex difference is unrelated to any of the moderator variables we have studied.It was not possible to carry out a meta-analysis of degree of handedness due to wide-spread differences in the method of reporting of degree of handedness.We recommend that future studies of handedness should, as a minimum, use one of three standard methods of assessment, so that comparison of studies is facilitated. Note: This manuscript was originally prepared in 1993 but due to problems at a major journal, described briefly, was never eventually published. It has however been cited on a number of occasions, and has been available at https://www.ucl.ac.uk/medical-education/publications/unpublished-manuscripts/meta-analysis-of-handedness . A major meta-analysis of handedness in 2019 by another author has now been submitted which cites this manuscript, and therefore it needs to be available in a more archivable format.

uoksimaa et al. 2009 ). Although a level of 25% for the contribution of additive genetic factors to the overall variation does not appear to be consistent with the original formulations of the Annett or McManus models, without genotyping data it is not possible to exclude the existence of individual loci of strong effect on the handedness phenotype. To date, linkage and association studies have been confined to relatively few individuals ( Francks et al. , 2002 , 2007 ; Scerri et al. , 2011 ), so that there has been relatively low power to definitively exclude the existence of major loci influencing human handedness. In particular, alleles at LRRTM1 and PCSK6 implicated in linkage to or association with handedness in learning-disabled subjects have not been replicated in cohorts of non-disabled individuals ( Francks et al. , 2002 , 2007 ; Scerri et al. , 2011 ). Other approaches to explaining the observed patterns of familial clustering for variation in cerebral asymmetry have been suggested, including the emergence of variation in handedness from gene-culture interactions ( Laland, 2008 ) or from the combination of a fixed right-shift factor with variation due to (transmissible) epigenetic modification ( Crow, 2009 ). The availability of platforms for genome-wide typing of common genetic polymorphisms allows a different approach to determining the possible genetic basis for the determination of human handedness. Any allele underlying the models of McManus or of Annett, or any other simple genetic model in which handedness is determined by the inheritance of a pair of alleles, would need to have both a high frequency in the population (to account for the approximately 10% incidence of left-handedness) and to exert a strong individual effect on handedness phenotype. If so, such an allele should be effectively tagged by modern SNP-typing platforms, and even relatively small sample sizes should allow detection of highly significant association with handedness. In effec

A review of evidence for a genetic component in the determination of handedness. Experimental evidence is marshalled in support of some arguments for a significant genetic component in the transmission of human handedness. Studies of infantile lateral asymmetries and their correlation with cerebral dominance, certain highly heritable traits, and handedness are discussed. Published in Behavior genetics (1976)

Across time and place, right hand preference has been the norm, but what is the precise prevalence of left- and right-handedness? Frequency of left-handedness has shaped and underpinned different fields of research, from cognitive neuroscience to human evolution, but reliable distributional estimates are still lacking. While hundreds of empirical studies have assessed handedness, a large-scale, comprehensive review of the prevalence of handedness and the factors that moderate it, is currently missing. Here, we report 5 meta-analyses on hand preference for different manual tasks and show that left-handedness prevalence lies between 9.3% (using the most stringent criterion of left-handedness) to 18.1% (using the most lenient criterion of nonright-handedness), with the best overall estimate being 10.6% (10.4% when excluding studies assessing elite athletes' handedness). Handedness variability depends on (a) study characteristics, namely year of publication and ways to measure and classify handedness, and (b) participant characteristics, namely sex and ancestry. Our analysis identifies the role of moderators that require taking into account in future studies on handedness and hemispheric asymmetries. We argue that the same evolutionary mechanisms should apply across geographical regions to maintain the roughly 1:10 ratio, while cultural factors, such as pressure against left-hand use, moderate the magnitude of the prevalence of left-handedness. Although handedness appears as a straightforward trait, there is no universal agreement on how to assess it. Therefore, we urge researchers to fully report study and participant characteristics as well as the detailed procedure by which handedness was assessed and make raw data publicly available. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Exceptions to the male advantage on a spatial task: family handedness and college major as factors identifying women who excel. Two factors, family handedness and college major, were investigated in order to identify the characteristics of women likely to excel on a mental rotation task. It was found that those likely to have the necessary combination of genetic potential and spatial experiences were right-handed women with nonright-handed relatives, majoring in math-science fields. Across three samples, this subgroup significantly outperformed all other groups of undergraduate women and did as well as undergraduate men on the Vandenberg Mental Rotation Test. This study provides new information on possible genetic and environmental factors influencing mental rotation ability in women. Published in Neuropsychologia (1989)

Handedness conversion in children and parental handedness. In order to find out which factor, genetic or environmental, is more involved in determining hand usage, the distribution of handedness in Japanese senior high school students and the success of their parents' attempts at conversion of handedness was investigated with respect to four pairings of parental handedness. When a child's handedness was related to that of the parent, children of a left-handed parent were more likely to be non-right-handed than those of both right-handed parents. There was no significant relation between parental handedness and the rate of handedness conversion of children. The results are in favor of the view that human handedness is genetically rather than forcibly determined by parents, although environmental factors such as parents' interference are involved in decreasing the incidence of non-right-handedness in Japan. Published in Folia psychiatrica et neurologica japonica (1985)

Humans exhibit a striking and near-universal population-level right-hand preference, an evolutionary singularity unmatched among primates. Despite its pervasiveness, the origins of this lateralization remain poorly understood. Here, we combine phylogenetic comparative methods with meta-analysis to investigate manual lateralization across 41 anthropoid species (n = 2,025), testing longstanding eco-evolutionary hypotheses for handedness direction (mean handedness index, MHI) and strength (mean absolute handedness index, MABSHI). Our models reveal significant phylogenetic signal for both traits and identify Homo sapiens as an evolutionary outlier, exhibiting exceptional rightward bias and strength relative to phylogenetic expectations. However, this outlier status disappears when brain size (endocranial volume) and intermembral index are included, suggesting these factors are central to the emergence of human handedness. We also show that high MABSHI evolved early in hominin evolution, while MHI increased to unparalleled levels with the appearance of the genus Homo. Our findings identify bipedalism and neuroanatomical expansion as likely key drivers of uniquely human lateralization, while also revealing broader ecological patterns shaping handedness across primates. This work provides a framework for disentangling human-specific adaptations from general primate trends in the evolution of behavioral asymmetries.

Humans exhibit a striking and near-universal population-level right-hand preference, an evolutionary singularity unmatched among primates. Despite its pervasiveness, the origins of this lateralisation remain poorly understood. Here, we combine phylogenetic comparative methods with meta-analysis to investigate manual lateralisation across 41 anthropoid species (n = 2,025), testing longstanding eco-evolutionary hypotheses for handedness direction (MHI) and strength (MABSHI). Our models reveal significant phylogenetic signal for both traits and identify Homo sapiens as an evolutionary outlier, exhibiting exceptional rightward bias and strength relative to phylogenetic expectations. However, this outlier status disappears when brain size (endocranial volume, ECV) and intermembral index (IMI) are included, suggesting these factors are central to the emergence of human handedness. We also show that high MABSHI evolved early in hominin evolution, while MHI increased to unparalleled levels with the appearance of the genus Homo . Our findings implicate bipedalism and neuroanatomical expansion as key drivers of uniquely human lateralisation, while also revealing broader ecological patterns shaping handedness across primates. This work provides a framework for disentangling human-specific adaptations from general primate trends in the evolution of behavioural asymmetries.

Satz, 1979). Suppose that handedness is usually determined by genetic factors (e.g., Annett, 1985; Hicks … 1975) left-handedness is determined by a combination of genetic and non-genetic factors. The majority … reviewed the human handedness literature and found little support for the hypothesis that handedness is learned