Schizotypy and altered digit ratios: a second look

Assessing social cognition in patients with schizophrenia and healthy controls using the reading the mind in the eyes test (RMET): a systematic review and meta-regression

The reading the mind in the eyes test (RMET) - which assesses the theory of mind component of social cognition - is often used to compare social cognition between patients with schizophrenia and healthy controls. There is, however, no systematic review integrating the results of these studies. We identified 198 studies published before July 2020 that administered RMET to patients with schizophrenia or healthy controls from three English-language and two Chinese-language databases. These studies included 41 separate samples of patients with schizophrenia (total n = 1836) and 197 separate samples of healthy controls (total n = 23 675). The pooled RMET score was 19.76 (95% CI 18.91-20.60) in patients and 25.53 (95% CI 25.19-25.87) in controls (z = 12.41, p < 0.001). After excluding small-sample outlier studies, this difference in RMET performance was greater in studies using non-English v. English versions of RMET (Chi [Q] = 8.54, p < 0.001). Meta-regression analyses found a negative association of age with RMET score and a positive association of years of schooling with RMET score in both patients and controls. A secondary meta-analysis using a spline construction of 180 healthy control samples identified a non-monotonic relationship between age and RMET score - RMET scores increased with age before 31 and decreased with age after 31. These results indicate that patients with schizophrenia have substantial deficits in theory of mind compared with healthy controls, supporting the construct validity of RMET as a measure of social cognition. The different results for English versus non-English versions of RMET and the non-monotonic relationship between age and RMET score highlight the importance of the language of administration of RMET and the possibility that the relationship of aging with theory of mind is different from the relationship of aging with other types of cognitive functioning.

Empathic accuracy in individuals with schizotypal personality traits

Empirical research using the Empathic Accuracy Task (EAT) has suggested that schizophrenia patients and people with schizotypal personality disorder exhibit lower empathic accuracy than healthy people. However, empathic accuracy in a subclinical sample with high levels of schizotypy has seldom been studied. Our study aimed to investigate empathy in a subclinical sample using the Chinese version of the EAT and a self-report empathy measure. Forty participants with high levels of schizotypy (HS participants) and 40 with low levels of schizotypy (LS participants), as measured by the Schizotypal Personality Questionnaire (SPQ), were recruited. All participants completed the Chinese version of the EAT and the self-report Questionnaire of Cognitive and Affective Empathy. Empathic accuracy (EA) scores and the intra-individual variability of EA scores were calculated. Independent samples t tests and Pearson correlation analyses were performed to examine group differences in empathy and the relationship between empathy and schizotypy respectively. HS participants exhibited reduced EA for both positive and negative videos, and larger intra-individual variability of EA for negative videos than LS participants. However, HS and LS participants did not differ in self-report cognitive empathy. Moreover, the interpersonal dimension of the SPQ was negatively correlated with EAT performance and self-report cognitive empathy in LS participants. Individuals with HS show poorer performance-based EA but relatively intact self-report cognitive empathy. This study provides empirical evidence for the ontogeny of empathy deficits in subclinical populations at risk of developing schizophrenia, supporting early interventions for social cognitive deficits.

Theory of mind in schizotypy: A behavioral and event-related potential (ERP) study

Background

Schizophrenia is known for their theory of mind (ToM) impairment. However, this impairment in schizotypy (schizotypal traits) lacks investigation.

Aims

The present study investigated: (1) whether ToM ability was impaired in schizotypy; (2) whether the ERP amplitudes in nine brain regions of interest associated with ToM (e.g., frontal region) in schizotypy and healthy controls differed; and (3) whether the relationship between ToM performances and ERP amplitudes in schizotypy differed from that in healthy controls.

Method

Forty eight adolescents and young adults (16 schizotypy) with the mean age of 18 years were tested. The Reading the Mind in the Eyes Test (RMET) was used to assess their ToM during which ERP amplitudes were recorded.

Results

The schizotypy group showed significantly lower ERP amplitudes in all conditions of RMET in frontal, frontal-central, central, occipital and temporal regions when compared to those in healthy controls. Also, schizotypy's ERP amplitudes in the frontal, frontal-central, central, occipital, and temporal regions were different from those in the healthy individuals in responding to different types of ToM stimuli (positive, negative and neutral). In schizotypy group, reaction time responding to emotional stimuli was negatively related to ERP amplitudes in the frontal, central-parietal, parietal, occipital, and occipito-temporal regions during RMET while no significant correlations were found in healthy controls.

Conclusion

The present findings inform us with the knowledge regarding the neural and behavioral abnormality of ToM in schizotypy, suggesting that brain activity can be an alternative to detect ToM impairment in schizotypy.

[Theory of mind and schizotypy: A review]

OBJECTIVES

Schizophrenia spectrum disorders are associated with incapacitating social impairments, mostly due to Theory of Mind (ToM) deficits. Theory of mind difficulties often precede the beginning of schizophrenia spectrum disorders and contribute highly to the social withdrawal of patients. They also predict bad outcome for individuals suffering from this condition. The use of samples of individuals presenting subclinical forms of schizophrenia spectrum disorders constitute an opportunity to study theory of mind capacities. Notably, the study of theory of mind deficits in schizotypy allows a better understanding of predictive markers of schizophrenia spectrum disorders. They also contribute to the identification of primary processes involved in social difficulties associated with these disorders.

METHODS

We searched PubMed, Science Direct and Google Scholar databases for peer-reviewed articles studying the association between theory of mind performance and schizotypal traits up to the 1 April 2020. The following syntax was used: schizotypy AND ("theory of mind" OR "social cognition" OR "irony" OR "false belief" OR "social inference" OR "hinting task"). We also checked the references from these articles for additional papers. Only English and French written articles were considered.

RESULTS

Twenty-three articles were included in the review. The majority of these studies (n=20) used behavioral measures of theory of mind (i.e. percentages of correct responses on a theory of mind task). Only a few (n=3) recent studies used brain imaging to study theory of mind in psychometric schizotypy. In those 23 studies, 18 report theory of mind difficulties in individuals with high schizotypal traits. Ten out of these 19 studies report an association between positive schizotypy and theory of mind deficits/hypomentalizing. The positive dimension was the most associated with theory of mind difficulties. The negative dimension was associated with theory of mind deficits in six studies out of 19 (33 %). The association between disorganization and theory of mind deficits was weak, mostly because of a lack of studies measuring this dimension (only one study out of 13 measured this particular trait). The association between hypermentalizing and schizotypy was poorly characterized, due to high heterogeneity in how this feature was conceptualized and measured. In summary, some authors consider good performance on a theory of mind task as a sign of hypermentalizing, while other authors consider that this feature relates to the production of erroneous interpretations of mental states. We advocate in favor of the second definition, and more studies using this framework should be conducted. Interestingly, the three studies using fMRI showed no significant behavioral differences between high and low schizotypal groups on theory of mind performance, while the patterns of brain activation differed. This shows that in individuals with schizotypy, theory of mind anomalies are not always captured just by behavioral performance. Brain imagery should be included in more studies to better understand theory of mind in schizotypy. In general, high heterogeneity in ways of assessing schizotypy, and in the tasks used to evaluate theory of mind, were found. Notably, some tasks require shallower theory of mind processing than others. It is a priority to design theory of mind tasks that allow for manipulating the difficulty of the items within one task, as well as the level of help that can be given, in order to allow for a better assessment of the impact of theory of mind difficulties and the ways to compensate for them.

CONCLUSIONS

The studies included in this review confirm the association between psychometric schizotypy and theory of mind. But the high heterogeneity in methods used in these studies, and notably the diversity in ways of assessing schizotypal traits and theory of mind, hinder a precise description of such an association. Additional studies are required. In particular, fMRI studies using tasks allowing for a precise description of altered and preserved theory of mind processes could be of great use in characterizing theory of mind difficulties associated with schizotypy.

Theory of mind and schizotypy: A meta-analysis

Schizotypy is a multi-dimensional personality construct that putatively indicates an individual's liability to psychosis. Schizophrenia is associated with significant deficits in theory of mind (ToM). However, previous studies investigating the relationship between schizotypy and ToM provided inconsistent findings. Following the systematic review of all relevant schizotypy studies between January 1, 1980 and June 30, 2019, a meta-analysis of the relationship between ToM and schizotypy was conducted. Current meta-analysis included 24 studies consisting of 4162 healthy individuals. Overall, there was a significant but a small negative relationship between ToM and schizotypy (d = -0.23, CI = -0.14-0.33). Schizotypy scores were negatively associated with both reasoning (d = -0.24, CI = -0.11-0.38) and decoding (d = -0.21, CI = -0.09-0.32) aspects of ToM. The relationship between ToM and schizotypy was more significant in the studies using extreme-group design (d = -0.31, CI = -0.17-0.45) than non-extreme-group design (d = -0.17, CI = -0.04-0.29). ToM abnormalities were significantly related to both positive and negative schizotypy. Current findings support the continuum between schizotpy and schizophrenia. ToM abnormalities might be vulnerability markers for psychosis.

Social cognition in schizophrenia: A network-based approach to a Taiwanese version of the Reading the Mind in the Eyes test

BACKGROUND

This study aimed to examine social-cognitive impairments in patients with schizophrenia using the Eyes test. In contrast to previous methods using the correct answers, we developed the Taiwanese version of the Eyes test and constructed the response network to explore impairments in the emotional aspects of theory of mind in patients with schizophrenia.

METHODS

Eighteen patients with schizophrenia and 18 healthy controls were recruited to examine their performance of the Eyes test. To explore the internal structures of mental states, we used network analysis to construct the networks of choice patterns (i.e. participants' answers) by using two network indicators, including density (an index of structure diversity of a network) and centrality (an index of the choice patterns within a network). Moreover, we divided all the choices into negative, positive, and neutral item groups based on emotion polarity.

RESULTS

The patient group was slower and less accurate than the control group. Moreover, there was a negative correlation between accuracy and blunted affect, and there were positive correlations between reaction time and emotional withdrawal and apathetic social withdrawal. As compared to healthy controls, patients with schizophrenia showed larger density in the network structure and higher centrality than controls. Also, patients showed poorer performance on negative words than healthy controls.

CONCLUSION

Our results demonstrated more diversity to recognize negative emotions from patients' choice patterns as compared to those in the control group. These findings suggest that deficits on recognizing negative emotions might be associated with the dysfunctions of mental states in schizophrenia.

What Do You Have in Mind? Measures to Assess Mental State Reasoning in Neuropsychiatric Populations

Social interaction is closely associated with both functional capacity and well-being. Previous research has not only revealed evidence of social dysfunction in individuals with a wide range of psychiatric and neurological disorders but also generated an abundance of potential measures for assessing social cognition. This review explores the most popular measures used within neuropsychiatric populations to investigate the ability to recognize or reason about the mental states of others. Measures are also critically analyzed in terms of strengths and limitations to aid task selection in future clinical studies. The most frequently applied assessment tools use verbal, visual or audiovisual forms of presentation and assess recognition of mental states from facial features, self-rated empathy, the understanding of other's cognitive mental states such as beliefs and intentions, or the ability to combine knowledge of other's thoughts and emotions in order to understand subtle communications or socially inappropriate behavior. Key weaknesses of previous research include limited investigation of relationships with clinical symptoms, and underutilization of measures of everyday social functioning that offer a useful counterpart to traditional "lab" tasks. Future studies should aim to carefully select measures not only based on the range of skills to be assessed but also taking into account potential difficulties with interpretation and the need to gain insight into the application of social cognitive skills as well as ability per se. Some of the best measures include those with well-matched control trials (e.g., Yoni Task) or those that restrict the influence of verbal deficits (e.g., intentions comic strip task), elicit spontaneous mentalizing (e.g., Animations Task), and possess greater ecological validity (e.g., Movie for the Assessment of Social Cognition). Social cognitive research within psychiatric populations will be further enhanced through the development of more closely matched control tasks, and the exploration of relationships between task performance, medication, strategy use, and broader emotional and motor functions.

Second-to-fourth digit length ratio is associated with negative and affective symptoms in schizophrenia patients

BACKGROUND

Higher levels of circulating oestrogens in women and testosterone in men have been shown to have a protective effect against the clinical manifestations of schizophrenia, mostly with respect to negative symptomatology. Certain studies suggest that they also have a protective effect against the neuropsychological impairment observed in the disease. We investigated whether greater prenatal exposure to estrogens in women and to testosterone in men, reflected by the 2D:4D ratio, was similarly associated with decreased negative symptomatology and improved neuropsychological functioning in patients.

METHOD

51 schizophrenia patients and 50 healthy participants were administered a neuropsychological battery. The 2D:4D ratio was measured in all participants. Positive, negative, and affective symptoms were assessed in patients. Regression analyses were conducted separately in male and female subgroups.

RESULTS

No associations with positive symptoms were revealed. In male patients, the 2D:4D ratio was positively associated with avolition and inversely associated with anxiety. In female patients, it was inversely associated with alogia, and tended to be positively associated with depression. No association between higher prenatal concentration of the relevant sex hormone and improved neuropsychological performance emerged in patients.

CONCLUSIONS

Higher concentrations of prenatal testosterone in male patients, and prenatal oestrogens in female patients, are associated with a decrement in certain aspects of negative symptomatology. In addition, prenatal sex hormone concentration seems to be associated with predisposition to anxiety in male patients, and to depression in female patients.

Age of pubertal onset and 2nd to 4th digit ratios: Preliminary findings

BACKGROUND

The second to fourth digit ratio (2D:4D) is used as a marker of prenatal sex hormone exposure. The aim of this study was to evaluate the possible relation between digit ratio and age of pubertal onset.

METHODS

Participants were 321 men and 202 women aged between 18 and 28 at the time of assessment who self-reported their onset of puberty (i.e., age at first conscious ejaculation or menarche). Participants' right and left digit lengths were measured from hand scans.

RESULTS

All groups of males, i.e., early, average, and late pubertal onset, had lower mean 2D:4D than the comparable female groups, regardless of the relative timing of their pubertal onset. Among the males, there was a significant difference in digit ratios between individuals who experienced early, average, and late onset of puberty. In the males, we observed a positive relationship between 2D:4D and age of pubertal onset for both right and left hands. There were no significant differences in 2D:4D among the three groups of female maturers. We observed no significant association between digit ratios and age at menarche.

CONCLUSIONS

These data lend further support for using 2D:4D as a measure of prenatal androgen exposure.

Asymmetry and empathy: Higher asymmetry is associated with lower levels of mentalizing

People differ in their mentalizing abilities. Though past research suggests that individual differences in exposure to prenatal testosterone may be able to explain why some people excel at mentalizing, while others struggle, meta-analyses yield a null relationship between 2D:4D ratio (a proxy for prenatal testosterone) and mentalizing. Importantly, however, past research has not examined the asymmetrical differences between the digit ratios on the right and left hands. In the current work, we test whether the difference between the digit ratios of the left and right hands may function as a better predictor of mentalizing than digit ratio alone. In Study 1, we begin by validating an online, self-report measure of 2D:4D ratio, providing test-retest reliability, convergent, and concurrent validity for our measure. In Study 2, we demonstrate that a) 2D:4D is quadratically related to asymmetry, b) asymmetry is negatively associated with mentalizing, and c) the relationship between asymmetry and mentalizing cannot be explained by the relationship between asymmetry and short-term memory. Taken together, our results paint a more nuanced picture of the relationship between digit ratio and mentalizing ability.

Emotion processing deficits in the different dimensions of psychometric schizotypy

Schizotypy refers to a personality structure indicating "proneness" to schizophrenia. Around 10% of the general population has increased schizotypal traits, they also share other core features with schizophrenia and are thus at heightened risk for developing schizophrenia and spectrum disorders. A key aspect in schizophrenia-spectrum pathology is the impairment observed in emotion-related processes. This review summarizes findings on impairments related to central aspects of emotional processes, such as emotional disposition, alexithymia, facial affect recognition and speech prosody, in high schizotypal individuals in the general population. Although the studies in the field are not numerous, the current findings indicate that all these aspects of emotional processing are deficient in psychometric schizotypy, in accordance to the schizophrenia-spectrum literature. A disturbed frontotemporal neural network seems to be the critical link between these impairments, schizotypy and schizophrenia. The limitations of the current studies and suggestions for future research are discussed.

Digit ratio (2D:4D) in a Chinese population with schizophrenia

BACKGROUND

Prenatal gonadal hormones may play a major role in pathogenesis of schizophrenia. It has been reported that second to fourth digit ratio (2D:4D) was influenced by the levels of exposure to prenatal testosterone and estrogen. So, 2D:4D may help to predict the disease susceptibility to schizophrenia.

AIMS

The aim of this study was to investigate the relationship between the digit ratio (2D:4D) and schizophrenia in Chinese population.

METHODS

We recruited 178 schizophrenics (males: 76; females: 102) and 365 controls (males: 218; females: 147) in this study. Photocopies of both hands were collected and left hand, right hand, mean hand and left minus right hand (DL-R) 2D:4D were analyzed.

RESULTS

The right and mean hand 2D:4D ratios were significantly higher in schizophrenics compared to that of controls in both males and females. The left hand 2D:4D ratio in female schizophrenics was also significantly higher than in controls. Compared to controls, the DL-R 2D:4D in male schizophrenics was obviously higher. There was a weakly (but not significantly) negative correlation between the mean hand 2D:4D ratio and the age of onset.

CONCLUSIONS

The 2D:4D ratio may correlate with the schizophrenia in Chinese population, and it may be an indicator of schizophrenia.

Schizotypy, autobiographical memory, and theory of mind: sex differences

Individuals with schizophrenia exhibit a range of cognitive impairments, including tasks assessing theory of mind (ToM) and autobiographical memory (AM). This study appears to be the first to examine how ToM and AM abilities interact in relation to schizotypy. Forty-seven undergraduate students reporting a wide continuous range of scores on the Schizotypal Personality Questionnaire (SPQ) completed a measure of ToM and a measure assessing various phenomenological qualities of AM. Female participants exhibited a negative correlation between the ToM score and the SPQ total score and a positive correlation between enhanced phenomenological qualities of AM and the SPQ disorganized factor score. No statistically significant relationships were found for male participants. ToM was negatively correlated with AM across the entire sample, which was not moderated by sex or schizotypy. It is possible that distinct underlying mechanisms account for the observed sex differences on ToM and AM performance in schizophrenia-related conditions.

Oxytocin, testosterone, and human social cognition

I describe an integrative social-evolutionary model for the adaptive significance of the human oxytocinergic system. The model is based on a role for this hormone in the generation and maintenance of social familiarity and affiliation across five homologous, functionally similar, and sequentially co-opted contexts: mothers with offspring, female and male mates, kin groups, individuals with reciprocity partners, and individuals within cooperating and competing social groups defined by culture. In each situation, oxytocin motivates, mediates and rewards the cognitive and behavioural processes that underlie the formation and dynamics of a more or less stable social group, and promotes a relationship between two or more individuals. Such relationships may be positive (eliciting neurological reward, reducing anxiety and thus indicating fitness-enhancing effects), or negative (increasing anxiety and distress, and thus motivating attempts to alleviate a problematic, fitness-reducing social situation). I also present evidence that testosterone exhibits opposite effects from oxytocin on diverse aspects of cognition and behaviour, most generally by favouring self-oriented, asocial and antisocial behaviours. I apply this model for effects of oxytocin and testosterone to understanding human psychological disorders centrally involving social behaviour. Reduced oxytocin and higher testosterone levels have been associated with under-developed social cognition, especially in autism. By contrast, some combination of oxytocin increased above normal levels, and lower testosterone, has been reported in a notable number of studies of schizophrenia, bipolar disorder and depression, and, in some cases, higher oxytocin involves maladaptively 'hyper-developed' social cognition in these conditions. This pattern of findings suggests that human social cognition and behaviour are structured, in part, by joint and opposing effects of oxytocin and testosterone, and that extremes of such joint effects partially mediate risks and phenotypes of autism and psychotic-affective conditions. These considerations have direct implications for the development of therapies for alleviating disorders of social cognition, and for understanding how such disorders are associated with the evolution of human cognitive-affective architecture.

Latent factor modeling of four schizotypy dimensions with theory of mind and empathy

Preliminary evidence suggests that theory of mind and empathy relate differentially to factors of schizotypy. The current study assessed 686 undergraduate students and used structural equation modeling to examine links between a four-factor model of schizotypy with performance on measures of theory of mind (Reading the Mind in the Eyes Test [MIE]) and empathy (Interpersonal Reactivity Index [IRI]). Schizotypy was assessed using three self-report measures which were simultaneously entered into the model. Results revealed that the Negative factor of schizotypy showed a negative relationship with the Empathy factor, which was primarily driven by the Empathic Concern subscale of the IRI and the No Close Friends and Constricted Affect subscales of the Schizotypal Personality Questionnaire. These findings are consistent with a growing body of literature suggesting a relatively specific relationship between negative schizotypy and empathy, and are consistent with several previous studies that found no relationship between MIE performance and schizotypy.

A critical review of the research on the extreme male brain theory and digit ratio (2D:4D)

Boys are more likely than girls to be diagnosed with an autism spectrum disorder (ASD). The extreme male brain (EMB) theory of ASD suggests that fetal testosterone (FT) exposure may underlie sex differences in autistic traits. A link between the organizational effects of FT on the brain and ASD is often drawn based on research using digit ratio (2D:4D), a putative biomarker, without a full survey of the findings. This paper critically and quantitatively reviews the research on the relationship between 2D:4D and ASD as well as autism spectrum, empathizing, and systemizing measures in neurotypical populations. Overall, there is some support for the EMB theory in all four areas, particularly the 2D:4D-ASD relationship. Recommendations for future research are provided.

The 2D:4D ratio of the hand and schizotypal personality traits in schizophrenia patients and healthy control persons

Prenatal estrogen/testosterone exposure is known to be involved in early brain development. In this context, the ratio of the index finger to ring finger length (2D:4D) has been put forward as an indicator of the intrauterine sex hormonal level. A previous study by Collinson et al. (2010) examined 2D:4D ratios in Asian patients with schizophrenia and found an increased 2D:4D pattern in male patients compared to male healthy controls. In the current study, we tried to replicate the result of this study on the 2D:4D ratio in schizophrenia patients and controls in a Chinese sample. Moreover, we investigated the link between 2D:4D ratios and schizotypal personality traits in the participants of the study. No significant difference between cases and controls in 2D:4D ratios for both hands could be observed. However, a positive association between right 2D:4D ratio and schizotypal personality traits was found in healthy controls (both in the male and female subsamples) suggesting that a high 2D:4D ratio could represent a vulnerability factor for schizophrenia in healthy males and females. Same results were observed for the digit ratio of the left hand and the SPQ in the healthy total and healthy female subsample. Therefore, the inclusion of personality measures to study the link between the digit ratio and schizophrenia might help to provide insights in a potential continuum from healthy to schizophrenic behavior.

A multidimensional assessment of social cognition in psychometrically defined schizotypy

Individuals with schizophrenia exhibit impairments in multiple social cognitive domains. There is evidence that these impairments may be trait-related vulnerability markers for schizophrenia. However, the literature focusing on individuals vulnerable to developing schizophrenia-spectrum disorders, referred to as schizotypy, has produced inconsistent findings. This study's primary aim was to provide a more comprehensive understanding of social cognitive functioning within schizotypy than previous studies by employing a broad array of measures to assess multiple social cognitive domains, and examine how these domains relate to specific schizotypy traits (i.e., positive, negative, and disorganized) and Quality of Life (QOL). Facial emotion recognition, Theory of Mind (ToM), and aspects of emotional intelligence related to regulating one's own emotions (emotion management) and other's emotions (social management) were measured. Individuals with psychometrically defined schizotypy (n=36) and controls (n=26) were examined. The schizotypy group performed significantly worse than controls on facial emotion recognition, ToM, and emotion management, but not social management. Generally speaking, poorer social cognition performance was not a function of specific schizotypy traits. However, negative traits were associated with poorer facial emotion recognition, and disorganized traits were associated with better social management. Facial emotion recognition was associated with QOL in the schizotypy group.

The "Reading the Mind in the Eyes" test: systematic review of psychometric properties and a validation study in Italy

INTRODUCTION

The "Reading the Mind in the Eyes" test (henceforth, Eyes test) is a simple but advanced Theory of Mind test, and it is widely used across different cultures. This study assessed the reliability and construct (convergent and discriminant) validity of the Eyes test in Italy.

METHODS

A sample of 18- to 32-year-old undergraduate students of both sexes (N=200, males=46%) were invited to fill in the Italian version of the Eyes test, the Empathy Quotient (EQ), the Toronto Alexithymia Scale (TAS), and the Marlowe-Crowne Social Desirability Scale (SDS).

RESULTS

Internal consistency (Cronbach's alpha) was .605. Confirmatory factor analysis provided evidence for a unidimensional model, with maximal weighted internal consistency reliability=.719. Test-retest reliability for the Eyes test, as measured by intraclass correlation coefficient, was .833 (95% confidence interval=.745 to .902). Females scored significantly higher than males on both the Eyes test and the EQ, replicating earlier work. Those participants who scored lower than 30 on the EQ (n=10) also scored lower on the Eyes test than those who did not (p<.05). Eyes test scores were not related to social desirability.

CONCLUSIONS

This study confirms the validity of the Eyes test. Both internal consistency and test-retest stability were good for the Italian version of the Eyes test.

Hint, hint: theory of mind performance in schizotypal individuals

Studying Theory of Mind (ToM) performance in nonclinical populations may assist our understanding of underlying cognitive processes and contributing factors. ToM was assessed in three groups of psychometrically identified schizotypes, namely, individuals elevated on scales assessing positive schizotypy, those elevated on scales assessing negative schizotypy, and those elevated on both positive and negative schizotypy scales, using two hinting tasks. Individuals characterized by positive schizotypy showed poorer ToM performance compared with controls. The results suggest that individuals with elevated positive schizotypy scores experience more difficulty inferring the meaning of others' mental states (i.e., intentions) via indirect speech, such as hints. The negative schizotypy group did not differ from the nonschizotypy group in ToM performance. These findings are considered in terms of cognitive processing styles and implications for possible intervention. They also provide support for the inclusion of multiple groups of schizotypal individuals when assessing social cognition.

Hemispheric asymmetry and theory of mind: is there an association?

INTRODUCTION

In autism and schizophrenia attenuated/atypical functional hemispheric asymmetry and theory of mind impairments have been reported, suggesting common underlying neuroscientific correlates. We here investigated whether impaired theory of mind performance is associated with attenuated/atypical hemispheric asymmetry. An association may explain the co-occurrence of both dysfunctions in psychiatric populations.

METHODS

Healthy participants (n=129) performed a left hemisphere (lateralised lexical decision task) and right hemisphere (lateralised face decision task) dominant task as well as a visual cartoon task to assess theory of mind performance.

RESULTS

Linear regression analyses revealed inconsistent associations between theory of mind performance and functional hemisphere asymmetry: enhanced theory of mind performance was only associated with (1) faster right hemisphere language processing, and (2) reduced right hemisphere dominance for face processing (men only).

CONCLUSIONS

The majority of non-significant findings suggest that theory of mind and functional hemispheric asymmetry are unrelated. Instead of "overinterpreting" the two significant results, discrepancies in the previous literature relating to the problem of the theory of mind concept, the variety of tasks, and the lack of normative data are discussed. We also suggest how future studies could explore a possible link between hemispheric asymmetry and theory of mind.

Patterns of second-to-fourth digit length ratios (2D:4D) in two species of frogs and two species of lizards at La Selva, Costa Rica

It is now well documented that androgen and estrogen signaling during early development cause a sexual dimorphism in second-to-fourth digit length ratio (2D:4D). It is also well documented that males of mammalian species have a smaller 2D:4D than females. Although there are discrepancies among 2D:4D studies in birds, the consensus is that birds exhibit the opposite pattern with males having a larger 2D:4D than females. The literature currently lacks substantial information regarding the phylogenetic pattern of this trait in amphibians and reptiles. In this study, we examined 2D:4D in two species of frogs (Oophaga pumilio and Craugastor bransfordii) and two species of lizards (Anolis humilis and Anolis limifrons) to determine the existence and the pattern of the sexual dimorphism. Male O. pumilio and C. bransfordii displayed larger 2D:4D than females in at least one of their two forelimbs. Male A. humilis had larger 2D:4D than females in both hindlimbs, but smaller 2D:4D than females in both forelimbs. Male A. limifrons may also have smaller 2D:4D than females in the right forelimb. Finally, digit ratios were sometimes positively related to body length, suggesting allometric growth. Overall, our results support the existence of the 2D:4D sexual dimorphism in amphibians and lizards and add to the knowledge of 2D:4D trait patterning among tetrapods.

Theory of Mind and psychometric schizotypy

The extent to which Theory of Mind impairments are a trait associated with schizotypy is unclear. To date, findings have been mixed. We compared two groups of psychometrically identified schizotypes, namely, those characterized by positive schizotypy (perceptual aberrations and magical ideation; n=36) and those characterized by negative schizotypy (social anhedonia; n=30) to a low schizotypy comparison group (n=68) in terms of their Theory of Mind performance. Theory of Mind was assessed in two ways: a composite Hinting Task and the Reading the Mind in the Eyes Test. The groups were also compared in terms of their self-reported levels of referential thinking. Our results indicate that individuals characterized by positive schizotypy show Theory of Mind deficits, as measured by the Hinting Task. The three groups did not differ in terms of the Eyes Test. Referential thinking was significantly associated with the Eyes Test but not the Hinting Task. Overall these findings suggest that different aspects of schizotypy are associated differentially with Theory of Mind deficits. The results also provide further rationale for the inclusion of multiple tasks when attempting to study multifaceted constructs such as Theory of Mind.