Ambidexterity and magical ideation

Blots and brains. A note on the centenary of Hermann Rorschach's death

This historical note is a commemorial of Rorschach, the person, and Rorschach the test. Hermann Rorschach died 100 years ago, not quite a year after the publication of his book containing the 10 inkblots. These have reached an iconic status, but the "Rorschach Test" as used in psychiatry, legal organizations and aptitude assessments is not quite what Hermann Rorschach designed it for in the first line. A first section of this article introduces Hermann Rorschach as a man with very broad interests and an inclination to ask cognitive science questions that are still challenging today. A second section provides a critical summary of the fate of the ten inkblots after Rorschach's death - how they conquered the whole world in a time with a pronouced "psychometric attitude", and also how they failed in some attempts to measure personality traits in special populations. A final section focuses on recent research on one particular aspect of a testee's associations to the inkblots: "movement responses", i.e. the perception of implied motion. Here, neural and behavioral correlates have been demonstrated by modern neuroimaging techniques. One study, which set out to validate both the Rorschach as a personality test and the view that the two cerebral hemispheres correspond to divergent "personalities" is also summarized. The viewpoint concludes by suggesting that future work with inkblots should consider Rorschach's original intention to use inkblots to uncover basic laws of perception. Modern applications of computer-generated pseudorandom stimuli (random dot arrays or stochastic noise) would have been embraced by Hermann Rorschach as he appreciated the impact of visual noise for the study of vision and visual cognition.

Ambiguous handedness and visuospatial pseudoneglect in schizotypy in physical and computer-generated virtual environments

Virtual reality (VR) technology has increased clinical attention in the health care of schizophrenia spectrum disorders in both diagnoses of the symptoms and assessment of schizotypal traits. However, the exact nature of VR-induced positive treatment effect in schizotypy is still unknown. In this study, VR technology was used as a non-invasive neurocognitive trigger to test the asymmetric visuospatial representational instability found in individuals with high schizotypy. The study aimed to reveal the brain functional hemispheric laterality in physical and virtual realities in individuals with schizotypal traits. Fifty-one healthy, right-handed participants (24 males and 27 females) were enrolled through public advertisements. Hemispheric functional asymmetry was measured by the Line Bisection Task (LBT). The results revealed that (a) LBT bias in the physical reality showed a handedness-related leftward pseudoneglect, however, similar handedness-related pseudoneglect in VR has not been found. (b) Comparing LBT bias in physically real and VR environments showed rightward drift in VR environments independently to the degree of handedness. (c) The schizotypy has no association with handedness, however, the cognitive schizotypy is related to the LBT bias. Higher cognitive schizotypy in VR associated with left hemispatial pseudoneglect. In conclusion, schizotypy is associated with ambiguous behavioral and cognitive functional laterality. In individuals with high cognitive schizotypy, the VR environment enhanced the representational articulation of the left hemispace. This effect may be originated from the enhancement of the right hemisphere overactivation and is followed by a lower mental control of the overt behavior.

When the wheels come off: Actor-network therapy for mental health recovery in the bicycle repair workshop

Professional accounts of emotional distress originate from within mainstream mental illness discourses and are underpinned by largely conjectural biomedical, brain-based conceptions of disorder. Alternative, formulation-based approaches remain delimited by cultural norms and linguistic resources. Service users frequently declare the most ordinary aspects of therapy the most helpful: listening, understanding, and respectfulness; these are not contingent upon the presence of a mental health professional. This paper describes ameliorations in states of emotional distress amongst volunteer trainee mechanics in a bicycle workshop, which has little overtly to do with mental health. Possible explanations for these ameliorations, or 'recoveries', are presented. In an enabling setting that offers the social and material resources conducive to particular ways of being, an applied actor-network approach is introduced as a practical way to disentangle the concomitant complexities of bicycles and everyday life. This approach to analysing states of distress-introduced here as 'actor-network therapy'-combines notions of enactment and enhandedness in the appreciation of 'engrenage' - the intriguing intricacy of locally generated, provisional realities.

Authoritarianism, Conspiracy Beliefs, Gender and COVID-19: Links Between Individual Differences and Concern About COVID-19, Mask Wearing Behaviors, and the Tendency to Blame China for the Virus

The present study investigated variables potentially associated with a lack of concern about COVID-19 and belief in the conspiracy theory that China is responsible for the virus. In particular, the study looked at Authoritarianism, Conspiracy Beliefs, gender, and consistency of handedness as predictors of nine Likert-type items gauging attitudes, behavior, and beliefs regarding the virus. Initial analyses showed that Authoritarianism predicted less concern about the impact of the virus on health, less mask wearing, and a stronger belief in China's responsibility for the illness. Conspiracy Beliefs were associated with a stronger belief in China's responsibility. Women expressed greater degrees of concern about their own and others' health and about the financial wellbeing of others. In order to reduce the number of dimensions, and thus the number of tests that could yield a type one error, the nine items were then submitted to a principal components analysis which yielded a "Concern about COVID" factor and a "Blame for China" factor. Authoritarianism is generally associated with less concern about the virus. In addition, men showed less concern about the virus overall than women. Both Authoritarianism and Conspiracy Beliefs accounted for unique variance in blame on China for the virus.

Handedness and the 2016 U.S. Primaries: consistent handedness predicts support for Donald Trump among republicans, but gender predicts support for Hillary Clinton among democrats

A growing number of studies demonstrate that consistent handers, people who use their dominant hand for all or most manual tasks, are less cognitively flexible than inconsistent handers, people who use their non-dominant hands at least some of the time. A recent hypothesis suggests that differences in handedness emerged evolutionarily because populations benefited from a balance between cognitively rigid and cognitively flexible people. One expectation is that cognitively rigid consistent handers would support more authoritarian policies or candidates. To test this idea, we looked at handedness, gender, and political affiliation as predictors of support for Donald Trump, a candidate whose supporters self-report being more authoritarian, in the 2016 primary. Our data show that in the Republican Primary, consistent handers report more support than inconsistent for Donald Trump. When authoritarianism was added as a covariate, the handedness effect disappeared. Further analyses showed that authoritarianism mediates the relationship between handedness and support for Donald Trump. In the Democratic Primary, there was a main effect of gender. Women reported more support than men for Hillary Clinton.

Semantic priming and schizotypal personality: reassessing the link between thought disorder and enhanced spreading of semantic activation

The term schizotypy refers to a group of stable personality traits with attributes similar to symptoms of schizophrenia, usually classified in terms of positive, negative or cognitive disorganization symptoms. The observation of increased spreading of semantic activation in individuals with schizotypal traits has led to the hypothesis that thought disorder, one of the characteristics of cognitive disorganization, stems from semantic disturbances. Nevertheless, it is still not clear under which specific circumstances (i.e., automatic or controlled processing, direct or indirect semantic relation) schizotypy affects semantic priming or whether it does affect it at all. We conducted two semantic priming studies with volunteers varying in schizotypy, one with directly related prime-target pairs and another with indirectly related pairs. Our participants completed a lexical decision task with related and unrelated pairs presented at short (250 ms) and long (750 ms) stimulus onset asynchronies (SOAs). Then, they responded to the brief versions of the Schizotypal Personality Questionnaire and the Oxford-Liverpool Inventory of Feelings and Experiences, both of which include measures of cognitive disorganization. Bayesian mixed-effects models indicated expected effects of SOA and semantic relatedness, as well as an interaction between relatedness and directness (greater priming effects for directly related pairs). Even though our analyses demonstrated good sensitivity, we observed no influence of cognitive disorganization over semantic priming. Our study provides no compelling evidence that schizotypal symptoms, specifically those associated with the cognitive disorganization dimension, are rooted in an increased spreading of semantic activation in priming tasks.

Telling right from right: the influence of handedness in the mental rotation of hands

BACKGROUND

This study investigated the impact of handedness on a common spatial abilities task, the mental rotation task (MRT). The influence of a right-handed world was contrasted with people's embodied experience with their own hands by testing both left- and right-handed people on an MRT of right- and left-hand stimuli. An additional consideration is the influence of matching the shape of the hand stimuli with the proprioception of one's own hands. Two orthogonal hypothesis axes were crossed to yield four competing hypotheses. One axis contrasted (i) embodied experience versus (ii) world knowledge; the other axis contrasted (a) the match between the visual image of a hand on the screen and one's own hand versus (b) the resemblance of the shape outline information from the hand stimuli with the proprioception of one's own hands.

RESULTS

Among people with mixed handedness, right-handers performed more accurately for left-hand stimuli, while left-handers had a trend for higher accuracy for right-hand stimuli. For people with extreme handedness, right-handers outperformed left-handers. Regardless of group, there was no significant variation in performance for left-hand stimuli, with only right-hand stimuli producing significant variation.

CONCLUSIONS

No hypothesis fully aligned with all the data. For left-hand stimuli, the consistent performance across groups does not provide support for embodied experience, while world knowledge might influence all groups similarly. Alternatively, the within-group variation for mixed-handed people supports embodied experience in the hand MRT, likely processed through visual-proprioceptive integration.

The Pen Is Not Always Mightier: Different Ways of Measuring Handedness With the Edinburgh Handedness Inventory Yield Different Handedness Conclusions

Although consistency of handedness (the strength of dominant hand preference) is increasingly recognized as an important individual difference, there are questions about how to best measure it. A recent meta-analysis showed that researchers have often failed to report details of responses and response formats to handedness test items. In addition to measuring handedness direction (i.e., left versus right handedness), there can be utility to dichotomizing the Edinburgh Handedness Inventory (EHI) into consistent and inconsistent dominant handedness, despite controversy over the best means of doing so. In this study, we performed a discriminant function analysis of EHI items to determine which items best predicted handedness consistency versus handedness direction. Although the same discriminant function accounted for most of the variance for both dependent measures, writing and drawing EHI items were the strongest predictors of handedness direction and combing and opening jars items were the strongest predictors of handedness consistency. As different items on the EHI predicted these different handedness dimensions, we discuss the implications of dichotomizing EHI items into both relevant dimensions for both biological and environmental theories of the basis of handedness and for future handedness research.

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.

Individual differences in apology acceptance and forgiveness: the influence of handedness

The purpose of the current study was to determine if the relationship between interhemispheric interaction and cognitive flexibility extends to explanations of forgiveness and apology acceptance. A growing body of research indicates that consistency of handedness may be reflective of an individual's degree of interhemispheric interaction and access to processes of the right hemisphere. As such, individual differences in processing that require interhemispheric interaction, such as belief updating, are associated with consistency of handedness. Participants completed the Edinburgh Handedness Inventory (EHI) and read descriptions of interpersonal transgressions, then rated their willingness to forgive before and after an apology was offered. There was a main effect such that the presence of apology increased forgiveness. However, inconsistent handedness was associated with greater forgiveness prior to apology compared to consistent handedness. A second study was conducted to determine if the individual differences in forgiveness were mediated by different dimensions of empathy (personal distress, perspective taking, empathic concern and fantasy). Participants completed the Interpersonal Reactivity Index, the Forgiveness Scale and the EHI. Results revealed those with inconsistent handedness who scored lower on personal distress reported decreased negative thoughts about transgressors compared to those with consistent handedness.

The association between inconsistent handedness and psychopathy does not extend to the domain of moral reasoning

A recent study [Shobe, E., & Desimone, K. (2016). Inconsistent handers show higher psychopathy than consistent handers. Laterality: Asymmetries of Body, Brain and Cognition, 21(2), 143-160. doi:10.1080/1357650X.2015.1089879] found an association between inconsistent handedness (the use of one's non-dominant hand for some tasks) and psychopathy. Because this provides evidence for an association between an individual difference and a trait that is perceived negatively, the present study set out to (1) attempt to replicate the finding and (2) determine whether inconsistent handedness and psychopathy predict similar patterns of moral reasoning. An Mturk sample of 344 adults took the Edinburgh Handedness Inventory, the Short Dark Triad Questionnaire, and the Moral Foundations Questionnaire. The finding of a modest association between handedness and psychopathy was replicated. However, handedness and psychopathy predicted totally different response patterns on the Moral Foundations Questionnaire, with psychopathy predicting less concern for others and fairness and inconsistent handedness predicting less respect for authority and less in group loyalty.

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.

The Many Sides of Hemispheric Asymmetry: A Selective Review and Outlook

Hemispheric asymmetry is commonly viewed as a dual system, unique to humans, with the two sides of the human brain in complementary roles. To the contrary, modern research shows that cerebral and behavioral asymmetries are widespread in the animal kingdom, and that the concept of duality is an oversimplification. The brain has many networks serving different functions; these are differentially lateralized, and involve many genes. Unlike the asymmetries of the internal organs, brain asymmetry is variable, with a significant minority of the population showing reversed asymmetries or the absence of asymmetry. This variability may underlie the divisions of labor and the specializations that sustain social life. (JINS, 2017, 23, 710-718).

Childrens' left-turning preference is not modulated by magical ideation

The literature on human turning preferences is inconsistent. While the few studies with children below 14 years of age uniformly describe an overall left-turning (counterclockwise) tendency, a recent Internet study with more than 1500 adults found a right-sided (clockwise) bias. We set out to investigate spontaneous turning behaviour in children age 5-3 years and, based on neuropsychiatric work in adults, also explored a potential association with magical thinking. Findings indicated a clear left-turning preference, independent of a participant's sex and handedness. Whether a child responded a question about the existence of extrasensory communication in the affirmative or not was unrelated to direction and size of turning bias and lateral preference. Our results are consistent with a left-sided turning preference reported for children, but in opposition to the clockwise bias recently described in a large-scale study with adults. Whether they point to a maturational gradient in the preferred direction of spontaneous whole-body rotation or rather to a lack of comparability between measures used in observational versus Internet-based studies remains to be further investigated. Regarding a purported association between body turns and magical thinking, our study is preliminary, as only one single question was used to probe the latter.

The PCSK6 gene is associated with handedness, the autism spectrum, and magical ideation in a non-clinical population

Common polymorphisms in the gene PCSK6, whose protein product mediates the development of brain and body asymmetry through the NODAL pathway, have recently been associated with handedness in three studies, making it a key candidate gene for understanding the developmental and expression of human lateralization. We tested the hypothesis that the PCSK6 VNTR polymorphism rs1053972 influences the expression of handedness and aspects of dimensional schizotypy and autism. For a sample of 709 healthy individuals, rs1053972 genotype was significantly associated with categorical measures of handedness, and with dimensional handedness in subsets of the population with high schizotypy and magical ideation or a lack of strong right-handedness. Both findings showed evidence of stronger or exclusive effects among females, compared to males. Genotypes of PCSK6 also showed significant sex-limited associations with magical ideation, a component of positive schizotypal cognition measured using the Schizotypal Personality Questionnaire, and total autism score, measured using the Autism Spectrum Quotient. These results partially replicate previous studies on effects of PCSK6 rs1053972 genetic variation on handedness phenotypes, link the PCSK6 gene with the dimensional expression of neurodevelopmental conditions in healthy individuals, and show that associations of this gene with handedness and psychological phenotypes exhibit evidence of sex-limited effects.

A systematic review on definitions and assessments of psychotic-like experiences

AIMS

Psychotic-like experiences (PLEs) or subclinical psychotic experiences have received increased attention as some studies have suggested continuity between PLEs and psychotic disorders. However, epidemiological and correlational studies of PLEs showed mixed findings - it is observed that different studies use a wide variety of definitions of PLEs, as well as different assessment tools that are designed to capture such described experiences. The differences in definitions and assessment tools adopted could contribute to the discrepancy of findings. The current review aims to examine the definitions and assessment tools adopted in the studies of PLEs.

METHODS

Literature search was conducted between October 2013 and February 2014 using three search engines: Medline, Web of Science and PubMed.

RESULTS

A total of 76 papers met the selection criteria and were included in the current review. It is found that the majority of papers reviewed defined PLEs quantitatively using assessment tools and do not have a specific phenomenological definition, whereas assessment tools adopted have a wide variety. Furthermore, phenomenological studies of PLEs were rare.

CONCLUSIONS

The variations in definitions and assessment tools of PLEs might contribute to mixed findings in researches. Reaching to a consensus through the study of phenomenology of PLEs is essential to further advancement of the research in this area.

Factor analysis of the Edinburgh Handedness Inventory: Inconsistent handedness yields a two-factor solution

While neuropsychology has long focused on direction (left versus right) of handedness, a growing body of evidence indicates that degree (inconsistent versus consistent) of handedness is at least as important. A promising feature of this new emphasis on degree of handedness is its greater concordance with extant genetic models of handedness, which posit a continuum from inconsistent-handedness to consistent right-handedness, not a continuum from left- to right-handedness. Specifically, departures away from consistent-right-handedness are thought to reflect the action of a neutral genetic factor that leaves handedness up to random environmental influences. To test whether handedness in inconsistent-handers reflects the presence of multiple factors (compared to the presence of a single factor only in consistent-right-handers), factor analyses of handedness inventory scores were conducted on data from 987 right-handers, divided into consistent- versus inconsistent-handers. Consistent with predictions, analyses of inconsistent- versus consistent-handers yielded two versus one factor solutions, respectively. Results are discussed in terms of their potential implications for genetic models of handedness and for researchers interested in consistency of handedness as a neuropsychological variable.

Handedness predicts motivation to switch from the status quo

Degree of handedness is a correlate of structural brain asymmetries and predicts individual differences in episodic memory, belief updating and various biases in decision-making. We examined whether handedness moderated the status quo bias given previous research suggests that both constructs are related to loss aversion. Participants answered hypothetical scenarios in which they decided either to stay with the status quo or to switch. Results indicated that consistent and inconsistent right-handers both exhibited status quo bias (Experiment 1; N=180), but inconsistent right-handers were more (or less) likely to stick with the status quo when informed of a positive (or negative) past experience. When provided with more equivocal information about the quality of the status quo and alternative, consistent-handers (CH) were more likely to show a status quo bias (Experiment 2; N=222). Compared to CH, we argue that inconsistent-handers (IH) more readily update their beliefs in a manner consistent with how the status quo and alternative options are presented-switching when finding a reason to favour the alternative and staying when the status quo is described more favourably. These handedness differences fit a motivational account explaining status quo bias rather than a loss aversion account.

Individual differences in information order effects: the importance of right-hemisphere access in belief updating

The order in which information is received alters the evaluation of causal hypotheses. Specifically, research suggests that the last piece of information oftentimes has the greatest impact on the evaluation and that the difference in subjective value between two pieces of information is an important factor influencing the magnitude of this recency effect. The present paper extends this line of work by exploring individual differences in this phenomenon via one's degree of handedness. Two hundred and five participants were given two hypothetical scenarios and related causal hypotheses accompanied by two pieces of additional information and asked to revise their belief in each hypothesis as information accumulated. Results confirmed predictions that 1) inconsistent/mixed-handers (those who use their non-dominant hand for at least some activities) show a larger effect with two pieces of inconsistent weak or strong information, and 2) neither mixed-handers nor consistent/strong-handers (those who use their dominant hand for almost all activities) show an effect with strong and weak pieces of consistent information. Mixed-handers' susceptibility to persuasive arguments and Ramachandran's (1995; Ramachandran and Blakeslee, 1998) belief-updating theory centered around communication between the two halves of the brain and functional access to the right hemisphere are used to account for these data.

Differences between left- and right-handers in approach/avoidance motivation: influence of consistency of handedness measures

Hand preference is often viewed as a troublesome variable in psychological research, with left-handers routinely excluded from studies. Contrary to this, a body of evidence has shown hand preference to be a useful variable when examining human behavior. A recent review argues that the most effective way of using handedness as a variable, is a comparison between individuals who use their dominant hand for virtually all manual activities (consistent handers) versus those who use their other hand for at least one activity (inconsistent handers). The authors contend that researchers should only focus on degree of handedness rather than direction of preference (left versus right). However, we argue that the field suffers from a number of methodological and empirical issues. These include a lack of consensus in choice of cut-off point to divide consistent and inconsistent categories and importantly a paucity of data from left-handers. Consequentially, researchers predominantly compare inconsistent versus consistent right-handers, largely linked to memory, cognition and language. Other research on response style and personality measures shows robust direction of handedness effects. The present study examines both strength and direction of handedness on self-reported behavioral inhibition system (BIS) and behavioral activation system (BAS) scores, using evidence from a large (N = 689) dataset including more than 200 left-handers. There were degree of handedness effects on BIS and BAS-Fun Seeking, but effects are largely driven by differences between consistent left-handers and other groups. Choice of cut-off point substantively influenced results, and suggests that unless a suitable sample of left-handers is included, researchers clarify that their degree of handedness effects are applicable only to right-handers. We concur that strength of hand preference is an important variable but caution that differences related to consistency may not be identical in right and left-handers.

Left brain, right brain: facts and fantasies

Handedness and brain asymmetry are widely regarded as unique to humans, and associated with complementary functions such as a left-brain specialization for language and logic and a right-brain specialization for creativity and intuition. In fact, asymmetries are widespread among animals, and support the gradual evolution of asymmetrical functions such as language and tool use. Handedness and brain asymmetry are inborn and under partial genetic control, although the gene or genes responsible are not well established. Cognitive and emotional difficulties are sometimes associated with departures from the "norm" of right-handedness and left-brain language dominance, more often with the absence of these asymmetries than their reversal.

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.

Individual differences in personality as a function of degree of handedness: consistent-handers are less sensation seeking, more authoritarian, and more sensitive to disgust

Prior research indicates that consistent-handedness is associated with decreased access to right hemisphere processing and consequent decreased cognitive flexibility. Handedness differences on three dimensions of personality related to cognitive flexibility were investigated. Experiment 1 found that consistent-handedness was associated with decreased sensation seeking. Experiment 2 found that consistent-handedness was associated with increased Right Wing Authoritarianism. Experiment 3 found that consistent-handedness was associated with increased sensitivity to disgust. Prior research has shown associations between decreased sensation seeking, increased authoritarianism, and increased disgust sensitivity, and consistent-handedness appears to underlie all of these associations. Personality researchers are encouraged to include handedness as a factor in analyses, as failure to do so can lead to systematic mis-estimation of sex differences due to the over-representation of females among consistent-handers.

Schizotypy and hemispheric asymmetry: Results from two Chapman scales, the O-LIFE questionnaire, and two laterality measures

Schizotypy is a multidimensional personality construct representing the extension of psychosis-like traits into the general population. Schizotypy has been associated with attenuated expressions of many of the same neuropsychological abnormalities as schizophrenia, including atypical pattern of functional hemispheric asymmetry. Unfortunately the previous literature on links between schizotypy and hemispheric asymmetry is inconsistent, with some research indicating that elevated schizotypy is associated with relative right over left hemisphere shifts, left over right hemisphere shifts, bilateral impairments, or with no hemispheric differences at all. This inconsistency may result from different methodologies, scales, and/or sex proportions between studies. In a within-participant design we tested for the four possible links between laterality and schizotypy by comparing the relationship between two common self-report measures of multidimensional schizotypy (the O-LIFE questionnaire, and two Chapman scales, magical ideation and physical anhedonia) and performance in two computerised lateralised hemifield paradigms (lexical decision, chimeric face processing) in 80 men and 79 women. Results for the two scales and two tasks did not unequivocally support any of the four possible links. We discuss the possibilities that a link between schizotypy and laterality (1) exists but is subtle, probably fluctuating, unable to be assessed by traditional methodologies used here; (2) does not exist, or (3) is indirect, mediated by other factors (e.g., stress-responsiveness, handedness, drug use) whose influences need further exploration.

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.

Degree of Handedness, but not Direction, is a Systematic Predictor of Cognitive Performance

A growing body of evidence is reviewed showing that degree of handedness (consistent versus inconsistent) is a more powerful and appropriate way to classify handedness than the traditional one based on direction (right versus left). Experimental studies from the domains of episodic memory retrieval, belief updating/cognitive flexibility, risk perception, and more are described. These results suggest that inconsistent handedness is associated with increased interhemispheric interaction and increased access to processes localized to the right cerebral hemisphere.

Cognitive disorganisation in schizotypy is associated with deterioration in visual backward masking

To understand the causes of schizophrenia, a search for stable markers (endophenotypes) is ongoing. In previous years, we have shown that the shine-through visual backward masking paradigm meets the most important characteristics of an endophenotype. Here, we tested masking performance differences between healthy students with low and high schizotypy scores as determined by the self-report O-Life questionnaire assessing schizotypy along three dimensions, i.e. positive schizotypy (unusual experiences), cognitive disorganisation, and negative schizotypy (introvertive anhedonia). Forty participants performed the shine-through backward masking task and a classical cognitive test, the Wisconsin Card Sorting Task (WCST). We found that visual backward masking was impaired for students scoring high as compared to low on the cognitive disorganisation dimension, whereas the positive and negative schizotypy dimensions showed no link to masking performance. We also found group differences for students scoring high and low on the cognitive disorganisation factor for the WCST. These findings indicate that the shine-through paradigm is sensitive to differences in schizotypy which are closely linked with the pathological expression in schizophrenia.

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.

Semantic organisation and handedness: mixed-handedness is associated with more diffuse activation of ambiguous word associates

Research indicates that there are individual differences in the flexibility and ease with which one retrieves and uses concepts stored in memory. Based on prior research suggesting that mixed-handedness is associated with greater cognitive flexibility, it was hypothesised that mixed-handers have access to a relatively diffuse associative network, where link strengths for closely related and distantly related concepts are not as disparate as in the case of strong-handers. This idea was explored using ambiguous words for stimuli, as ambiguous words are known to have both strong (concepts related via dominant meaning) and weak associates (concepts related via subordinate meaning). Consistent with the prediction, mixed-handers showed equal ease in accessing both strongly and weakly related concepts. In Experiment 1 mixed-handers exhibited equivalent priming for dominant and subordinate associates, while strong-handers exhibited priming for dominant associates only. In Experiment 2 ratings of strength of association for dominant versus subordinate associates were examined. Mixed-handedness was associated with lesser disparity of dominant and subordinate association ratings.

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.

The relationship between atypical semantic activation and odd speech in schizotypy across emotionally evocative conditions

INTRODUCTION

Odd speech is prevalent in individuals with schizotypy compared to controls and this odd speech is particularly pronounced under stress-induced conditions. Despite a number of research studies that have examined odd speech, the mechanisms underlying this phenomenon remain unclear. There is reason to suspect that the increase in odd speech observed in schizotypy may reflect atypical semantic activation patterns, defined in terms of increased activation of weakly associated words within the semantic network.

METHODS

In this study, we compared atypical semantic activation in individuals with a broad set of cognitive-perceptual, interpersonal and disorganization schizotypal traits (n=83) and controls (n=23). Odd speech was measured using a behavior-based analysis of natural speech procured from a laboratory speech-task involving separate experimentally manipulated stressful, pleasant, and neutral conditions.

RESULTS

The schizotypy and control groups did not differ in semantic activation, but atypical semantic activation was more pronounced in individuals with disorganization traits and attenuated in those with interpersonal traits. Interestingly, the relationship between semantic activation and odd speech was observed for the stressful, but not pleasant or neutral conditions in the schizotypy group.

CONCLUSIONS

These findings suggest that individuals with schizotypy may be able to inhibit atypical associations in nonstressful situations. However, their ability to prevent atypical semantic activation from affecting speech may be disrupted under stress, thus resulting in more odd speech. This study also highlights the dramatic differences in semantic activation across the various manifestations of schizotypy.

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.

Leftward bias in number space is modulated by magical ideation

BACKGROUND

Productive symptoms of schizophrenia and positive-symptom schizotypy have both been related to signs of right-sided hemispatial inattention ("pseudoneglect"). We here set out to explore, in healthy subjects, the relationship between one form of mild schizotypy ("magical ideation"; MI) and asymmetries in number space, which is a bias toward relatively small numbers, reportedly represented to the left of larger numbers.

METHODS

Forty right-handed participants filled in the MI scale and performed a number-line bisection (NLB) task and a randomization task (the Mental Dice Task, MDT, requiring randomization of the digits from 1 to 6).

RESULTS

We found pseudoneglect in number space, that is, more errors toward small numbers in the NLB task and an overproduction of small digits in the MDT. Individual participants' MI scores were correlated to the size of pseudoneglect in both numerical tasks.

CONCLUSIONS

Explicit (NLB) and implicit (MDT) assessments of the exploration of number space may be relevant to studies of the mechanisms underlying the formation of delusional and schizotypal beliefs. We propose that, in healthy subjects, a trait-like imbalance in hemispheric cooperation may not only produce asymmetries in physical and representational space, but also predisposes to develop magical ideas. Specifically, an over-proportional influence of the right hemisphere semantic system (preferentially coding oblique and remote associations) leads to the assumption of connections between randomly associated events.

Dopamine, Paranormal Belief, and the Detection of Meaningful Stimuli

Dopamine (DA) is suggested to improve perceptual and cognitive decisions by increasing the signal-to-noise ratio. Somewhat paradoxically, a hyperdopaminergia (arguably more accentuated in the right hemisphere) has also been implied in the genesis of unusual experiences such as hallucinations and paranormal thought. To test these opposing assumptions, we used two lateralized decision tasks, one with lexical (tapping left-hemisphere functions), the other with facial stimuli (tapping right-hemisphere functions). Participants were 40 healthy right-handed men, of whom 20 reported unusual, “paranormal” experiences and beliefs (“believers”), whereas the remaining participants were unexperienced and critical (“skeptics”). In a between-subject design, levodopa (200 mg) or placebo administration was balanced between belief groups (double-blind procedure). For each task and visual field, we calculated sensitivity (d′) and response tendency (criterion) derived from signal detection theory. Results showed the typical right visual field advantage for the lexical decision task and a higher d′ for verbal than facial stimuli. For the skeptics, d′ was lower in the levodopa than in the placebo group. Criterion analyses revealed that believers favored false alarms over misses, whereas skeptics displayed the opposite preference. Unexpectedly, under levodopa, these decision preferences were lower in both groups. We thus infer that levodopa (1) decreases sensitivity in perceptual–cognitive decisions, but only in skeptics, and (2) makes skeptics less and believers slightly more conservative. These results stand at odd to the common view that DA generally improves signal-to-noise ratios. Paranormal ideation seems an important personality dimension and should be assessed in investigations on the detection of signals in noise.