Schizophrenia Risk and Handedness: A Mixed Picture

Handedness as a neurodevelopmental marker in schizophrenia: Results from the FACE-SZ cohort

OBJECTIVES

High rates of non-right-handedness (NRH) including mixed-handedness have been reported in neurodevelopmental disorders. In schizophrenia (SZ), atypical handedness has been inconsistently related to impaired features. We aimed to determine whether SZ subjects with NRH and mixed-handedness had poorer clinical and cognitive outcomes compared to their counterparts.

METHODS

667 participants were tested with a battery of neuropsychological tests, and assessed for laterality using the Edinburg Handedness Inventory. Clinical symptomatology was assessed. Learning disorders and obstetrical complications were recorded. Biological parameters were explored.

RESULTS

The prevalence of NRH and mixed-handedness was high (respectively, 42.4% and 34.1%). In the multivariable analyses, NRH was associated with cannabis use disorder (p = 0.045). Mixed-handedness was associated with positive symptoms (p = 0.041), current depressive disorder (p = 0.005)), current cannabis use (p = 0.024) and less akathisia (p = 0.019). A history of learning disorder was associated with NRH. No association was found with cognition, trauma history, obstetrical complications, psychotic symptoms, peripheral inflammation.

CONCLUSIONS

Non-right and mixed-handedness are very high in patients with SZ, possibly reflecting a neurodevelopmental origin. NRH is associated with learning disorders and cannabis use. Mixed-handedness is associated with positive symptoms, current depressive disorder, cannabis use and less akathisia. However, this study did not confirm greater cognitive impairment in these patients.

Evolution of cerebral asymmetry

The human brain is often characterized in terms of a duality, with the left and right brains serving complementary functions, and even individuals are sometimes classified as either "left-brained" or "right-brained." Recent evidence from brain imaging shows that hemispheric asymmetry is multidimensional, comprised of independent lateralized circuits. Cerebral asymmetries, which include handedness, probably arise in phylogenesis through the fissioning of ancestral systems that divided and lateralized with increasing demand for specialization. They also vary between individuals, with some showing absent or reversed asymmetries. It is unlikely that this variation is controlled by a single gene, as sometimes assumed, but depends rather on complex interplay among several, perhaps many, genes. Hemispheric asymmetry has often been regarded as a unique mark of being human, but it has also become evident that behavioral and cerebral asymmetries are not confined to humans, and are widespread among animal species. They nevertheless exist against a fundamental background of bilateral symmetry, suggesting a tradeoff between the two. Individual differences in asymmetry, moreover, are themselves adaptive, contributing to the cognitive and behavioral specializations necessary for societies to operate efficiently.

Handedness and Attention Deficit/Hyperactivity Disorder Symptoms in College Students

The symptoms of adult Attention Deficit/Hyperactivity Disorder (ADHD) generally include impaired concentration; an insensitivity to social cues, being hard to get along with, and being internally restlessness. It is not surprising that these problems are likely to affect the performance of college students with ADHD. The study aims to examine whether ADHD symptoms are associated with handedness in college students in Taiwan. A total of 505 male and 645 female participants completed Annett's handedness questionnaire and the Traditional Chinese College ADHD Response Evaluation Student Response Inventory (C-CARE-SRI). Handedness was scored both categorically, mixed vs. not-mixed, and continuously, using the Hand Preference Index. The Inattention score was significantly higher for students who were mixed-handed than for those who were not, after social pressure against using the left hand to write had been adjusted for. However, the differences in Hyperactivity and Impulsivity scores were nonsignificant. In addition, the correlations between all three ADHD and Hand Preference Index factor-scores were nonsignificant. To sum up, mixed-handedness is associated with a higher Inattention score. The potential underlying mechanism relating to ADHD Inattention is discussed.

Handedness and schizotypy: The potential effect of changing the writing-hand

Mixed-handedness, which has been associated with schizotypy in recent studies, might exist for at least two different reasons: it is innate or it has been forced. We examined whether the association between mixed-handedness and schizotypy differs depending on its source. We enrolled 3485 college students in Taiwan. We used both the Perceptual Aberration Scale and Schizotypal Personality Questionnaire to assess schizotypy, and the Annett Hand Preference Questionnaire to assess handedness. Two ways of classifying handedness were examined: the three-way classification based on Annett's categories and mixed- vs. non-mixed-handedness based on Degree of Handedness. Both mixed-handedness groups showed higher positive schizotypy scores. Among mixed handers, those who had been required to change their writing hand from left to right had higher positive schizotypy scores. Being forced to change writing hand seemed to be related to a higher level of schizotypy. The potential effect of the social pressure against using the left hand for writing is discussed.

Motor behavior reflects reduced hemispheric asymmetry in the psychosis risk period

BACKGROUND

A body of work focusing on brain connectivity, language dominance, and motor laterality research suggests that reduced hemispheric asymmetry is a core feature in schizophrenia. However, there is little consensus about whether reduced dominance is present in those at ultrahigh risk (UHR) for psychosis.

METHODS

A total of 94 demonstrated right-handed neuroleptic free participants (38 UHR and 56 matched healthy controls) were assessed with structured clinical interviews and completed an innovative handwriting task using a digital tablet computer. A laterality quotient (LQ) was calculated using kinematic variables from the participant's left and right hands. A subset of the sample (26 UHR and 29 controls) returned after 12-months to complete clinical interviews in order to examine relationships between handwriting laterality and progression of psychosis risk symptoms.

RESULTS

The UHR group showed decreased dextrality compared to healthy controls. At the 12-month follow-up, decreased dextrality accounted for 8% of the variance in worsened positive symptoms within the UHR group.

CONCLUSION

The current results suggest that disrupted cerebral dominance is also present in the ultrahigh risk period and that decreased dextrality may serve as a novel biomarker for the progression of psychosis risk.

Negative correlation between leftward bias in line bisection and schizotypal features in healthy subjects

Introduction: Recent studies have found a lack of normal pseudoneglect in schizophrenia patients and in their first degree relatives. Similarly, several contributions have reported that measures of schizotypy in the healthy population may be related to signs of right-sided lateralization, but most of these studies differ greatly in methodology (sample size, choice of schizotypy scales, and laterality tasks) and, consequently, the results cannot be compared and so definitive conclusion cannot be drawn. In this study, our purpose is to investigate whether some tasks of spatial attention may be related to different dimensions of schizotypy not only in a larger sample of healthy subjects (HS), but testing the same people with several supposedly related measures several times.

Materials and Methods: In the first part of the study (Part I), the performance on “paper and pencil” line bisection (LB) tasks in 205 HS was investigated. Each task was repeated three times. In the second part of the study (Part II), a subgroup of 80 subjects performed a computerized version of the LB test and of the mental number line bisection (MNL) test. In both parts of the study, every subject completed the 74-item version of the Schizotypal Personality Questionnaire (SPQ) and the Edinburgh Handedness Inventory (EHI).

Results: In both parts of the study, high scores on the subscale “magical thinking” of SPQ have resulted in being closely linked to a decreased pseudoneglect as assessed by the LB task. On the contrary, right handedness is related to an increased leftward bias at the same task. No association was found between MNL and the other variables.

Discussion: The main finding of this study is that a decreased spatial leftward bias at the LB task correlates with positive schizotypy in the healthy population. This finding supports the hypothesis that a deviation from leftward hemispatial visual preference may be related to the degree of psychosis-like schizotypal signs in non-clinical population and should be investigated as a possible marker of psychosis.

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.

Psychotic-like symptoms and positive schizotypy are associated with mixed and ambiguous handedness in an adolescent community sample

The objective of this study was to replicate the association between atypical handedness and psychosis-proneness in a representative sample of adolescents from the general population. It expands previous studies by (1) analyzing a variety of atypical handedness indexes (left, mixed, ambiguous, and inconsistent), (2) measuring comprehensively the multidimensionality of psychosis-proneness, and (3) analyzing the association of different patterns of atypical handedness with nonclinical dimensions of both trait (schizotypy) and sub-clinical symptom (psychotic-like experiences) levels. Seven hundred and twenty-eight adolescents were assessed for handedness by the 12-item self-report Annett Hand Preference Questionnaire and for psychosis-proneness by the Oxford-Liverpool Inventory of Feelings and Experiences and the Community Assessment of Psychic Experiences scales. Writing-hand alone did not detect associations between laterality and psychosis-proneness. Mixed- rather than left-handedness was related to psychosis-proneness, and this was more evident when analyzing subjects with ambiguous handedness exclusively. When analysis was restricted to subjects with non-ambiguous handedness, strong left-handedness was related to psychosis-proneness. The positive dimension showed a stronger association than the negative one with atypical handedness. Results partially support mixed-handedness as a marker of developmental disorders underlying both atypical lateralization and psychosis-proneness. Among various possible mixed-handedness patterns, inconsistent hand use across primary actions, and for the same action across time, seems particularly related to psychosis-proneness and thus requires further exploration.

The cross-cultural nature of the relationship between schizotypy and mixed-handedness

Positive schizotypy is associated with non-right-handedness, which includes left- and mixed-handedness. However, because the underlying mechanisms might be different, it is important to examine whether both left- and mixed-handedness are associated with a high incidence of schizotypy. During 2009-2010, we used both the Perceptual Aberration Scale and Schizotypal Personality Questionnaire to assess 1315 undergraduate students in Taiwan for schizotypy and the Annett handedness questionnaire to assess handedness. Among the three-way classifications based on Annett's grouping, the fully left-handed group appeared to have the lowest score of positive schizotypy; next was the fully right-handed group and then the mixed-handed. Among the three-way classifications driven from cluster analysis, mixed-handers showed highest score of positive schizotypy. When handedness was treated continuously, both direction (e.g., Hand Preference Index) and consistency (e.g., Either hand use score) indicators were significantly correlated with schizotypy. The results of regression analyses showed that the quadratic handedness measure were negatively associated with schizotypy. The results remained similar after correcting for social pressure on left-handedness. In conclusion, the relationship between schizotypy and mixed-handedness appears to be cross-cultural. The dichotomous classification of handedness, right- vs. non-right-handedness, appears to be insufficient. Additional studies on the distinct mechanisms of mixed- and left-handedness are warranted.

Going beyond students: an association between mixed-hand preference and schizotypy subscales in a general population

Research on the sub-clinical condition of schizotypy suggests that it is associated with mixed handedness. To date, however, this research has focussed on undergraduate populations. If the association between schizotypy and mixed-handedness is the result of an underlying neurological trait, it is important to demonstrate that the effect extends to the general population. With this in mind, 699 participants were drawn from a wide community sample. Schizotypy was measured using the Psychosis Proneness Questionnaire and handedness was assessed using the Annett inventory. To avoid the sometimes arbitrary definitions of left-, right- and mixed-handed, regression analyses were used to explore the data. There was no evidence of a difference in schizotypy between individuals with a left- or right-hand preference. People with a mixed-hand preference, however, had higher scores on PER-MAG (Perceptual Aberration and Magical Ideation) and HYP-IMP (Hypomania and Impulsive Non-Conformity) scales (positive traits). No effect was observed for the SAN (Social Anhedonia) and PAN (Physical Anhedonia) scales (negative traits). The nature of the association between schizotypy and handedness observed in the current study is similar to that reported for student populations. The possibility that the association is related to response biases or a biological mechanism is discussed.

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

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

The evolution and genetics of cerebral asymmetry

Handedness and cerebral asymmetry are commonly assumed to be uniquely human, and even defining characteristics of our species. This is increasingly refuted by the evidence of behavioural asymmetries in non-human species. Although complex manual skill and language are indeed unique to our species and are represented asymmetrically in the brain, some non-human asymmetries appear to be precursors, and others are shared between humans and non-humans. In all behavioural and cerebral asymmetries so far investigated, a minority of individuals reverse or negate the dominant asymmetry, suggesting that such asymmetries are best understood in the context of the overriding bilateral symmetry of the brain and body, and a trade-off between the relative advantages and disadvantages of symmetry and asymmetry. Genetic models of handedness, for example, typically postulate a gene with two alleles, one disposing towards right-handedness and the other imposing no directional influence. There is as yet no convincing evidence as to the location of this putative gene, suggesting that several genes may be involved, or that the gene may be monomorphic with variations due to environmental or epigenetic influences. Nevertheless, it is suggested that, in behavioural, neurological and evolutionary terms, it may be more profitable to examine the degree rather than the direction of asymmetry.

Hand-preference and population schizotypy: a meta-analysis

Language functions in schizophrenia patients are represented more bilateral, i.e. less lateralized than in healthy subjects. This decreased lateralization is also observed in individuals at increased risk for schizophrenia. Language lateralization is related to handedness; in that left- and mixed-handed individuals more frequently have decreased lateralization in comparison to right-handed subjects. Population schizotypy can be considered part of the schizophrenia spectrum disorders. In line with this, population schizotypy has repeatedly, though inconsistently, been associated with left-handedness. In order to define the exact association between handedness and schizotypy, we performed meta-analyses on the available literature. We found that non-right-handed subjects, but not strong left-handers, had higher scores on schizotypy questionnaires than right-handed subjects. Mixed-handers showed a trend towards higher schizotypy in comparison to strong left-handers. It is argued that the higher schizotypy in non-right-handed individuals reflects the higher incidence of bilateral language lateralization in this group. Bilateral language organisation may underlie loosening of association, possibly leading to higher schizotypy scores.

Handedness and schizotypal features in healthy subjects

BACKGROUND

An excess of mixed-handedness has been repeatedly reported in schizophrenia and schizotypy. Handedness is a measure of atypical cerebral lateralization, which is considered as a risk factor for schizophrenia. Several studies have attempted to identify correlations between handedness and dimensions of psychosis but the results obtained so far remain inconclusive.

OBJECTIVE

To explore a possible link between mixed-handedness and the three classical dimensions of psychosis. As speech and language disorders may be associated with cerebral lateralization, we predicted a correlation between mixed-handedness and disorganized dimension.

METHODS

We used the Schizotypal Personality Questionnaire (SPQ) and the Edinburgh Handedness Inventory (EHI) to study the correlation between mixed-handedness scores and positive, negative or disorganized dimensions in a sample of 62 healthy subjects.

RESULTS

We found a negative correlation between mixed-handedness and the disorganized dimension of schizotypy, as individuals with prominent mixed-handedness showed more severe disorganization.

CONCLUSION

We have identified a link between mixed-handedness and the disorganized dimension that may help to identify genetic vulnerability factors involved in psychosis.

Mixed-handedness is associated with the reporting of psychotic-like beliefs in a non-clinical Italian sample

Atypical handedness has been repeatedly reported in schizophrenia, with quantitative review of evidence showing an increase of non-right-handedness in patients diagnosed with schizophrenia. Mixed-handedness is also higher among non-clinical people scoring high on questionnaires aimed at measuring psychosis-proneness. However, the greatest part of information on non-clinical samples came from samples collected in North America or in the UK: differences by countries in the socio-cultural pressure to use the right hand could influence the results. In this study 604 Italian non-clinical participants (248 males, 41.1%; 356 females, 58.9%; mean age=34.5+/-11.9) completed the Annett Hand Preference Questionnaire (HPQ), the General Health Questionnaire (GHQ), and the Peters et al. Delusions Inventory (PDI). In the sample, 527 subjects (87.3%) were classified on the HPQ as right-handed, 53 (8.8%) were classified as mixed-handed, and 24 (4.0%) were classified as left-handed. Mixed-handed scored statistically higher on the PDI than the right-handed and left-handed, but right-handed and left-handed did not differ from each other on a statistical ground. The difference by handedness was specific for PDI, since scores on the GHQ-12 did not differ by handedness group. The links between mixed-handedness and psychosis-proneness in non-clinical samples are a reliable finding, deserving further investigation as a model for the risk of schizophrenia.

Handedness and schizotypy in non-clinical populations: Influence of handedness measures and age on the relationship

This study aimed to evaluate the relation of handedness to schizotypal personality, with the influence of different handedness measures and age on the relationship investigated as well among representative samples of school students and community adults in Taiwan, where social pressure against certain left-handed actions was strong. In a total of 175 primary school students, 1020 junior high-school students, and 342 adult participants aged 20 to 65 years, all the participants completed the 12-item Annett handedness questionnaire, and the latter two groups further completed the Schizotypal Personality Questionnaire (SPQ) and the Perceptual Aberration Scale (PAS). There was a trend of increasing non-right handedness with younger age groups. Two classification methods in handedness, Annett's or Briggs-Nebes' three-category classification, led to very different frequency distribution and relation to schizotypy. For the adolescents, either Annett's classification or quantitative measures (Hand Preference Index and either-hand use scores) in handedness exhibited an association with schizotypy, whereas for the adults the either-hand use score was the only measure that did so. In contrast, no such difference was found using the Briggs-Nebes' classification method. The association of the non-right or mixed handedness was more consistent and of greater magnitude with the positive aspect of schizotypy, especially the PAS and the Cognitive-perceptual Dysfunction of the SPQ. The results highlight the potential of adolescents for future investigation on certain common causes underlying atypical cerebral lateralisation and positive schizotypy.

Mixed handedness is associated with the Disorganization dimension of schizotypy in a young male population

Within the ASPIS (Athens Study of Psychosis Proneness and Incidence of Schizophrenia) we sought out to examine in accordance with previous reports if a deviation from dextrality is associated with an augmented endorsement of self rated schizotypal personality traits in a large population of 1129 young male army recruits. Schizotypal traits were assessed using the Schizotypal Personality Questionnaire and hand preference membership was determined by applying stringent criteria derived from the Annett Handedness Questionnaire and the Porac-Coren questionnaire of lateral preferences. By adopting three different definitions of hand preference membership, we confirmed an association between mixed handedness and increased schizotypal personality traits, and in particular with Disorganization schizotypy that encompasses aspects of self perceived difficulties in verbal communication. Non-verbal cognitive ability, as indexed by measurement of non-verbal IQ, sustained attention and working memory was not associated with hand preference. We argue that a deviation from normal cerebral lateralization, as indexed by mixed handedness, is associated with mild sub clinical language dysfunction, rather than non-verbal cognitive ability, and this might be relevant to the expression of psychosis phenotype.

Schizotypy is increased in mixed-handers, especially right-handed writers who use the left hand for primary actions

Associations between schizotypy and handedness were examined in 733 undergraduates for the Sta and Unex scales of the O-LIFE inventory and several measures derived from the Annett hand preference questionnaire. Higher schizotypy scores were found for mixed-handers defined in various ways, including inconsistent preference for any item of the questionnaire and also the presence of either hand responses. There was a marked elevation of schizotypy scores (p<.001) for right-handed writers who prefer the left hand for other 'primary' actions (throwing, racket, match, hammer, toothbrush and scissors). This observation was replicated in 182 students assessed on the Rust Scale of Schizotypal Cognitions. Several findings agree that inconsistent hand preference is associated with a raised probability of schizotypal thinking.

Verbal creativity and schizotypal personality in relation to prefrontal hemispheric laterality: a behavioral and near-infrared optical imaging study

Although anecdotal and correlational results have suggested a reliable relationship between creativity and psychosis, few studies have examined this relationship using empirical methods. In addition, little is known about the neural substrates of creative thinking. We investigated the creative thinking process in relation to schizotypal personality, schizophrenia and prefrontal hemispheric laterality using behavioral and near-infrared optical spectroscopy (NIRS) methods. Schizophrenic, psychometrically ascertained schizotypal, and healthy control subjects (all right-handed) participated in a novel "alternate uses" task designed to assess divergent thinking (DT) ability. The DT task required subjects to generate "uses" for conventional and ambiguous objects. Prefrontal activity was measured using NIRS while subjects were engaged in DT vs. a cognitive control task in a subset of the subjects. Behavioral data indicated that schizotypes had enhanced DT ability compared with schizophrenic and control subjects, who showed similar performance overall. NIRS data showed that DT was associated with bilateral prefrontal cortex (PFC) activation, but the right PFC particularly contributed to the enhanced creative thinking in psychometric schizotypes compared with the other two groups. Thus, creative thinking seems to robustly recruit bilateral PFC, but it is the right PFC that is preferentially activated in schizotypes in relation to their enhanced DT.

Development of a version of the Schizotypy Traits Questionnaire (STA) for screening children

Schizotypy may be seen as both a dimension of normal individual differences and an indicator of the predisposition to schizophrenia and schizophrenia-spectrum disorders. Schizotypal traits have been widely investigated in adults but little research has explored schizotypy in younger samples. The aim of the present study was to examine the factor structure of schizotypal traits in a sample of normal children aged 11 to 15 years-a younger sample than investigated in the few previous studies. Schizotypal traits were assessed with the children's version of the adult Schizotypy Traits Questionnaire (STA). A principal components analysis was carried out on data from 317 subjects and yielded a three-factor solution, similar to several previous studies of adult samples. Factor one was characterised by unusual perceptual experiences, factor two by paranoid ideation/social anxiety, and factor three by magical thinking. The factor structure of the STA of this young sample was comparable with the previous studies of adults. The findings suggest that the children's version of STA is a scale suitable for the measurement of schizotypy in young populations, and that this scale could be useful in clinical assessment of children at risk for psychosis, as well as in research.

Ambidexterity and magical ideation

In a sample of 250 healthy undergraduate students, scores on a scale of magical ideation rose to a peak at the point of ambilaterality on a scale of hand preference, and fell away with increasing right- or left-handedness. This effect mirrors that reported by Crow, Crow, Done, and Leask (1998) who found a dip in academic abilities at the point of ambilaterality, or what they call ''the point of hemispheric indecision''. We relate these findings to genetic theories of laterality in which one allele (RS+) codes for left-cerebral dominance while the other (RS-) leaves laterality to chance. RS-- homozygotes may be susceptible to a lack of dominance, resulting in a disposition to magical ideation and an increased risk of schizophrenia, but also enhanced creativity and lateral thinking.

Schizotypy and the shift from dextrality: a study of handedness in a large non-clinical sample

Numerous previous studies have reported associations between schizophrenia/schizotypy and atypical handedness. While there is broad agreement that schizophrenia/schizotypy is associated with a shift away from typical (strong right) handedness, it is not entirely clear what aspect of atypical handedness is implicated: 'ambiguous' handedness (the absence of hand preference for given actions) or 'mixed handedness' (different hand preferences for different actions). The present study used several indices of handedness (derived from the Annett scale) to address these questions in 3000 + (mostly) University student subjects recruited by electronic mail. It was found that positive schizotypy (indexed by a scale of 'unusual experiences') was associated with both aspects of atypical handedness. These findings are discussed in the light of various possible explanations of the association between handedness and schizophrenia/schizotypy.