Relationships between autistic-like and schizotypy traits: An analysis using the Autism Spectrum Quotient and Oxford-Liverpool Inventory of Feelings and Experiences

Face perception and facial emotional expression recognition ability: Both unique predictors of the broader autism phenotype

Autism spectrum disorder (ASD) and the broader autistic phenotype (BAP) have been suggested to be associated with perceptual-cognitive difficulties processing human faces. However, the empirical results are mixed, arguably, in part due to inadequate samples and analyses. Consequently, we administered the Cambridge Face Perception Test (CFPT), the Reading the Mind in the Eyes Test (RMET), a vocabulary test, and the Autism Quotient (AQ) to a sample of 318 adults in the general community. Based on a disattenuated path analytic modelling strategy, we found that both face perception ability (β = -.21) and facial emotional expression recognition ability (β = -.27) predicted uniquely and significantly the Communication dimension of AQ. Vocabulary failed to yield a significant, direct effect onto the Communication dimension of the AQ. We conclude that difficulties perceiving information from the faces of others may contribute to difficulties in nonverbal communication, as conceptualised and measured within the context of BAP.

Assessing Restricted and Repetitive Behaviours in Online-Sampled Autistic and Non-autistic Individuals: Factor Structure of the Repetitive Behaviours Questionnaire for Adults (RBQ-2A)

The Repetitive Behaviours Questionnaire for Adults (RBQ-2A) measures two factors of restricted and repetitive behaviours (RRBs) associated with autism. However, the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) provides four criteria for RRBs: repetitive motor behaviours, insistence on sameness, restricted interests, and interest in sensory aspects of the environment (or atypical sensitivity). The current paper aimed to examine whether the RBQ-2A is a psychometrically sound measure of these four factors. Study 1 had university students (N = 368) complete the RBQ-2A and other related measures online and revealed that the RBQ-2A can assess the factors highlighted in the DSM-5 and that these four factors comprise a general RRB construct. Study 2 had individuals disclosing a diagnosis of autism (N = 283) complete the RBQ-2A and other related measures online and supported that this four-factor structure provided good psychometric properties. While the current paper provides findings for an online autistic population, further research is needed to generalize these findings to autistic individuals less likely to partake in online studies (e.g., those with intellectual or language disabilities). Overall, the results suggest that the RBQ-2A reliably and validly assesses RRBs.

Autistic traits specific to communication ability are associated with performance on a Mooney face detection task

Difficulties in global face processing have been associated with autism. However, autism is heterogenous, and it is not known which dimensions of autistic traits are implicated in face-processing difficulties. To address this gap in knowledge, we conducted two experiments to examine how identification of Mooney face stimuli (stylized, black-and-white images of faces without details) related to the six subscales of the Comprehensive Autistic Trait Inventory in young adults. In Experiment 1, regression analyses indicated that participants with poorer communication skills had lower task sensitivity when discriminating between face-present and face-absent images, whilst other autistic traits had no unique predictive value. Experiment 2 replicated these findings and additionally showed that autistic traits were linked to a reduced face inversion effect. Taken together, these results indicate autistic traits, especially communication difficulties, are associated with reduced configural processing of face stimuli. It follows that both reduced sensitivity for identifying upright faces amongst similar-looking distractors and reduced susceptibility to face inversion effects may be linked to relatively decreased reliance on configural processing of faces in autism. This study also reinforces the need to consider the different facets of autism independently.

The factor structure and measurement invariance of the Autism Spectrum Quotient-28: A cross-cultural comparison between Malaysia and the Netherlands

LAY ABSTRACT

The AQ-28 is a questionnaire measuring autistic traits, that is, traits that are related to Autism Spectrum Conditions, but its reliability in other cultures has not been thoroughly evaluated. We, therefore, tested whether the properties of the AQ-28 are comparable between two countries with different cultures, Malaysia and the Netherlands. A total of 437 Malaysian and 818 Dutch participants completed the AQ-28 online. We measured whether the AQ-28 measures autistic traits similarly in Malaysia and the Netherlands. The AQ-28 measures autistic traits similarly, and the reliability was acceptable and good in the general population of Malaysia and the Netherlands, respectively. However, Malaysians scored higher than Dutch participants. Moreover, 11 AQ-28 items showed cultural bias, indicating that these items are answered/interpreted differently in Malaysia and the Netherlands. Cross-cultural differences in interpreting, reporting, and/or expressing autistic traits highlighted in this study could potentially explain why some items are culturally biased and why Malaysians score higher on these items. The findings of this work imply that cutoff scores derived from one culture should not be generalised to another culture. Moreover, the findings are informative for future development of culturally neutral or appropriate screening and diagnostic tools for autism.

The three-factor structure of the Autism-Spectrum Quotient Japanese version in pregnant women

Background

There is a rising interest in perinatal mental health studies, and proper psychometric tools to assess autistic traits among this population in Japan are vital.

Objective

This study aimed to clarify the optimal factor structure of the AQ as part of a perinatal mental health research project.

Methods

We used the Japanese version of the AQ (AQ-J) to measure autistic-like traits in pregnant women. Participants were 4,287 Japanese women who were pregnant or who had given birth within the last month. We performed exploratory factor analysis (EFA) using the first sample group (n = 2,154) to obtain factor structures for the final item selections. We performed confirmatory factor analysis (CFA) using the second sample group (n = 2,133) to obtain a model with good fit, then compared the model to all previously proposed models to determine the best-fitting model.

Results

The EFA analysis identified a model consisting of 25 items distributed across three factors. Cronbach's alpha for the total 25-item AQ-J, 9-item "Social interaction" factor, 11-item "Non-verbal communication" factor, and 5-item "Restricted interest" factor was 0.829, 0.829, 0.755, and 0.576, respectively. McDonald's omega and its 95% confidence interval were 0.826 (0.821-0.836), 0.835 (0.821-0.837), 0.755 (0.744-0.766), and 0.603 (0.556-0.596), respectively. CFA confirmed that the three-factor structure had an acceptable fit (goodness of fit index: 0.900, comparative fit index: 0.860, root mean square error of approximation: 0.066). These findings indicated that the three-factor model was better than the 13 existing models.

Conclusion

The findings are discussed in relation to the adequacy of the AQ-J for assessing autistic traits in perinatal women. We recommend the use of this 25-item, three-factor AQ-J model for this population owing to its superiority to all previous models.

Gender bias in autism screening: measurement invariance of different model frameworks of the Autism Spectrum Quotient

BACKGROUND

The Autism Spectrum Quotient is a popular autism screening tool recommended for identifying potential cases of autism. However, many women with autism demonstrate a different presentation of traits to those currently captured by screening measures and assessment methods, such as the Autism Spectrum Quotient.

AIMS

Different models of the Autism Spectrum Quotient have been proposed in the literature, utilising different items from the original 50-item scale. Within good-fitting models, the current study aimed to explore whether these items assess autistic traits similarly across men and women.

METHOD

Seventeen Autism Spectrum Quotient models were identified from the literature. Using the responses of a large sample of adults from the UK general population (5246 women, 1830 men), confirmatory factor analysis was used to evaluate the fit of each model. Measurement invariance with respect to gender, adjusting for age, was explored in the 11 model frameworks that were found to have satisfactory fit to our data.

RESULTS

It emerged that only two items were gender invariant (non-biased), whereas for the remaining items, the probability of endorsement was influenced by gender. In particular, women had a higher probability of endorsing items relating to social skills and communication.

CONCLUSIONS

If the items of the Autism Spectrum Quotient indeed reflect autism-related traits, those items should be rephrased to ensure they do not present a gender-related bias. This is vital for ensuring more timely diagnoses and support for all people with autism.

Neural responses to biological motion distinguish autistic and schizotypal traits

Difficulties in social interactions characterize both autism and schizophrenia and are correlated in the neurotypical population. It is unknown whether this represents a shared etiology or superficial phenotypic overlap. Both conditions exhibit atypical neural activity in response to the perception of social stimuli and decreased neural synchronization between individuals. This study investigated if neural activity and neural synchronization associated with biological motion perception are differentially associated with autistic and schizotypal traits in the neurotypical population. Participants viewed naturalistic social interactions while hemodynamic brain activity was measured with fMRI, which was modeled against a continuous measure of the extent of biological motion. General linear model analysis revealed that biological motion perception was associated with neural activity across the action observation network. However, intersubject phase synchronization analysis revealed neural activity to be synchronized between individuals in occipital and parietal areas but desynchronized in temporal and frontal regions. Autistic traits were associated with decreased neural activity (precuneus and middle cingulate gyrus), and schizotypal traits were associated with decreased neural synchronization (middle and inferior frontal gyri). Biological motion perception elicits divergent patterns of neural activity and synchronization, which dissociate autistic and schizotypal traits in the general population, suggesting that they originate from different neural mechanisms.

General figure and face-specific closure ability: predictors of trait-autism?

Little research has examined the association between general figure closure speed, a stratum I ability within the Cattell-Horn-Carroll (CHC) model of intelligence, and face-specific closure ability; an important consideration, as some research suggests face processing is independent of other abilities. Additionally, figure closure ability (general and face) may correlate negatively with trait-autism, due to theorised autism-related difficulties in global processing. Therefore, in addition to developing a psychometrically robust short-form Mooney face detection task, we administered the Gestalt Figure Completion Test and the Autism Spectrum Quotient to a sample of 263 general community adults. We found convergent validity between face-specific and general figure closure ability (r = .44, 95%CI:[.30, .58]). Furthermore, based on a latent variable model, general figure closure ability was directly, and face-specific figure closure ability indirectly, negatively associated with trait-autism (i.e., nonverbal communication). We conclude that face detection ability evidences convergent validity with general figure closure ability and can be measured reliably in less than four minutes. Finally, a general, rather than face-specific, figure closure process may tap more directly into autism-like nonverbal communication ability, supporting the notion that global processing abilities of non-face objects may better reflect the requirements to ‘fill in the gaps’ in social contexts.

Connections between and within extended psychosis and autistic phenotypes and social relationships in the general population

OBJECTIVES

Non - clinical individuals with higher levels of autistic traits and psychotic experiences also have problems in social relationships. Therefore, this study aimed to model complex associations between autistic and psychotic phenotypes and indicators of social relationships in the general population using a network approach.

METHODS

The sample consisted of 649 participants with a mean age of M = 40.23 and SD = 13.09 sampled from the general population. The sample was representative for the 18-65 years old general population in the Slovak Republic. The following scales were administered: Community Assessment of Psychic Experiences, The Comprehensive Autistic Trait Inventory, and NIH Toolbox Adult Social Relationship Scales. Associations between variables and the presence of communities were identified using Exploratory Graph Analysis.

RESULTS

Results revealed four highly stable and densely connected communities within the network: social relationships, autistic traits, positive symptoms, and the last one consisting of all negative symptoms, problems in social interactions, and depression. The most important variables in the network were difficulties in social interaction, perceived rejection, bizarre ideas, depression, and social withdrawal.

CONCLUSIONS

The psychotic and autistic phenotypes in the general population showed a network of connections with characteristics of social relationships. Community detection revealed that autistic traits and psychotic-like experiences formed relatively independent communities. Further, there was substantial overlap between negative symptoms (e.g., social withdrawal), and core features of the autistic phenotype, especially social interaction difficulties.

Autism traits dimensionality and multivariate relationship with alexithymia and anxiety in the general population

BACKGROUND

Autism is characterized by social and non-social alterations observed beyond the clinical diagnosis. Research analyzing the expression of autism traits in the general population helps to unravel the relationship between autism dimensions and other associated variables, such as alexithymia and anxiety. The Autism-Spectrum Quotient (AQ) was developed to assess autism traits in the general population; however, inconsistent results regarding its dimensionality have emerged.

AIMS

This study aimed to extend evidence about the AQ measurement model, and explore the multivariate relationship between autism traits, alexithymia, and trait anxiety.

METHODS

292 adults of the general population were recruited. An Exploratory Factor Analysis and Confirmatory Factor Analysis were performed to assess the factorial structure of AQ. A path analysis was carried out to explore the relationship between autism traits, alexithymia, and trait anxiety.

RESULTS

The results supported a three-factor model of AQ. The path analysis model showed evidence of a significant role of alexithymia as a mediator of the relationship between autism traits and anxiety.

CONCLUSIONS AND IMPLICATIONS

The present study provides empirical support for a three-factor model of AQ in the general population. The association between autism traits, alexithymia, and anxiety dimensions highlights the multidimensional nature of these variables and the need to account for their distinct impact on autism-related variables.

Impaired Biological Motion Processing and Motor Skills in Adults with Autistic Traits

The present study explored the relationship between biological motion (BioM) processing, motor skills, and autistic traits within a non-clinical sample of 621 adults (18-73 years, 51.8% female). Results indicated that adults with greater autistic traits also endorsed difficulties associated with developmental coordination disorder (DCD) in childhood and adulthood. Traits associated with autism spectrum disorder and DCD were predictive of BioM processing abilities. The results also revealed sex differences in DCD, autistic traits, and BioM processing. Overall, these findings suggest that adults with greater autistic traits experience both deficits in motor activities as well as underlying motor perceptual abilities.

The effect of autistic traits on disembedding and mental rotation in neurotypical women and men

Recent data has revealed dissociations between social and non-social skills in both autistic and neurotypical populations. In the present study, we investigated whether specific visuospatial abilities, such as figure disembedding and mental rotation, are differently related to social and non-social autistic traits, in neurotypical women and men. University students (N = 426) completed the Autism Spectrum Quotient (AQ), figure disembedding and mental rotation of two-dimensional figures tasks. AQ social skills (AQ-social) and attention-to-details (AQ-attention) subscales were used as measures of social and non-social autistic traits, respectively. Mental rotation was affected by a significant interaction between sex, social and non-social traits. When non-social traits were above the mean (+ 1 SD), no sex differences in mental rotation were found. Instead, below this value, sex differences depended on the social traits, with men on average outperforming women at middle-to-high social traits, and with a comparable performance, and with women on average outperforming men, at lower social traits. A small positive correlation between figure disembedding and social traits was observed in the overall sample. These results are interpreted in terms of the hyper-systemizing theory of autism and contribute to the evidence of individual differences in the cognitive style of autistic people and neurotypical people with autistic traits.

Perceptual processing links autism and synesthesia: A co-twin control study

Synesthesia occurs more commonly in individuals fulfilling criteria for an autism spectrum diagnosis than in the general population. It is associated with autistic traits and autism-related perceptual processing characteristics, including a more detail-focused attentional style and altered sensory sensitivity. In addition, these characteristics correlate with the degree of grapheme-color synesthesia (consistency of grapheme-color associations) in non-synesthetes. We investigated a predominantly non-synesthetic twin sample, including individuals fulfilling criteria for an autism spectrum diagnosis or other neurodevelopmental disorders (n = 65, 14-34 years, 60% female). We modelled linear relationships between the degree of grapheme-color synesthesia and autistic traits, sensory sensitivity, and visual perception, both within-twin pairs (22 pairs) where all factors shared by twins are implicitly controlled (including 50-100% genetics), and across the entire cohort. We found that the degree of grapheme-color synesthesia was associated with autistic traits within the domain of Attention to Details and with sensory hyper-, but not hypo-sensitivity. These associations were stronger within-twin pairs than across the sample. Further, twins with a higher degree of grapheme-color synesthesia were better than their co-twins at identifying fragmented images (Fragmented Pictures Test). This is the first twin study on the association between synesthesia and autism-related perceptual features and traits. The results suggest that investigating these associations within-twin pairs, implicitly adjusting for potential confounding factors shared by twins, is more sensitive than doing so in non-related individuals. Consistent with previous findings, the results suggest an association between the degree of grapheme-color synesthesia and autism-related perceptual features, while utilizing a different measure for sensory sensitivity. The novel finding of enhanced fragmented picture integration in twins with a higher degree of grapheme-color synesthesia challenges the view of a generally more detail-focused attentional style in synesthesia and might be related to enhanced memory or mental imagery in more synesthetic individuals.

Anxiety Sensitivity Domains are Differently Affected by Social and Non-social Autistic Traits

Anxiety sensitivity (AS) is implicated in the development and maintenance of several psychopathological conditions. Non-clinical individuals with high autistic traits may develop anxiety disorders and depressive symptoms. Here, we investigated the relationships of autistic traits with AS dimensions and depression, considering sex. We referred to the two-factor model of the autism spectrum quotient to distinguish social and non-social autistic traits and assessed 345 university students on AS and depression scales. Results showed that only social autistic traits predicted general AS and anxiety-related concerns regarding social and cognitive domains. The present results emphasize the need of assessing multiple domains of anxiety in individuals on the autistic spectrum, differentiating social and non-social traits.

Brief Report: Facial Asymmetry and Autistic-Like Traits in the General Population

Atypical facial morphology, particularly increased facial asymmetry, has been identified in some individuals with Autism Spectrum Conditions (ASC). Many cognitive, behavioural and biological features associated with ASC also occur on a continuum in the general population. The aim of the present study was to examine subthreshold levels of autistic traits and facial morphology in non-autistic individuals. Facial asymmetry was measured using three-dimensional facial photogrammetry, and the Autism-spectrum Quotient was used to measure autistic-like traits in a community-ascertained sample of young adults (n = 289). After accounting for covariates, there were no significant associations observed between autistic-like traits and facial asymmetry, suggesting that any potential facial morphology differences linked to ASC may be limited to the clinical condition.

Is it Possible to Assess the Two-Domain Definition of the Broad Autism Phenotype Using the Available Measurement Tools?

Although, the operationalization of the autism spectrum disorder has been updated around two domains, the broad autism phenotype (BAP) one has not. Additionally, the items of the three common BAP measures, the Broad Autism Phenotype Questionnaire (BAPQ), the Autism Quotient, and the Social Responsiveness Scale (SRS), remain organized around a non-consensual number of factors. We explored whether the items of these measures matched with the two-domain operationalization through a parallel analysis, which has suggested two main components, and two expert judgments which have assessed item wording, relevance, and construct representativeness. A remaining pool of 48 BAP-relevant items suggested a possible under-representation of two subdomains. Despite the relevance of all the BAPQ items, only the SRS ones tapped in all subdomains.

Autistic Traits are Associated with Less Precise Perceptual Integration of Face Identity

Face recognition difficulties are common in autism and could be a consequence of perceptual atypicalities that disrupt the ability to integrate current and prior information. We tested this theory by measuring the strength of serial dependence for faces (i.e. how likely is it that current perception of a face is biased towards a previously seen face) across the broader autism phenotype. Though serial dependence was not weaker in individuals with more autistic traits, more autistic traits were associated with greater integration of less similar faces. These results suggest that serial dependence is less specialised, and may not operate optimally, in individuals with more autistic traits and could therefore be a contributing factor to autism-linked face recognition difficulties.

Co-occurrence of autistic and psychotic traits: implications for depression, self-harm and suicidality

BACKGROUND

There is increasing interest in the clinical and aetiological overlap between autism spectrum disorders and schizophrenia spectrum disorders, reported to co-occur at both diagnostic and trait levels. Individually, sub-clinical autistic and psychotic traits are associated with poor clinical outcomes, including increased depressive symptomatology, self-harming behaviour and suicidality. However, the implications when both traits co-occur remain poorly understood. The study aimed to (1) examine the relationship between autistic and psychotic traits and (2) determine if their co-occurrence increases depressive symptomatology, self-harm and suicidality.

METHODS

Cross-sectional data from a self-selecting (online and poster advertising) sample of the adult UK population (n = 653) were collected using an online survey. Validated self-report measures were used to assess sub-clinical autistic and psychotic traits, depressive symptomatology, self-harming behaviour and suicidality. Correlation and regression analyses were performed.

RESULTS

A positive correlation between sub-clinical autistic and positive psychotic traits was confirmed (r_s = 0.509, p < 0.001). Overall, autistic traits and psychotic traits were, independently, significant predictors of depression, self-harm and suicidality. Intriguingly, however, depression was associated with a negative interaction between the autistic domain attention to detail and psychotic traits.

CONCLUSIONS

This study supports previous findings that sub-clinical autistic and psychotic traits are largely independently associated with depression, self-harm and suicidality, and is novel in finding that their combined presence has no additional effect on depression, self-harm or suicidality. These findings highlight the importance of considering both autistic and psychotic traits and their symptom domains in research and when developing population-based depression prevention and intervention strategies.

Understanding Oneself to Understand Others: The Role of Alexithymia and Anxiety in the Relationships Between Autistic Trait Dimensions and Empathy

People on the autism spectrum may have difficulty inferring others' emotions (cognitive empathy), but may share another's emotions (affective empathy) and exhibit heightened personal distress. The present study examined independent autistic trait dimensions (social difficulties and restricted/repetitive behaviours) and the roles alexithymia and trait anxiety have in explaining this profile of empathy. Results from the general population (n = 301) revealed that pronounced social difficulties and not restricted/repetitive behaviours related to reduced cognitive and affective empathy, and heightened personal distress. However, both dimensions, through alexithymia and anxiety, indirectly influenced empathy. Surprisingly, while the dimensions indirectly improved affective empathy, pronounced social difficulties directly reduced affective empathy. This study motivates a nuanced model of empathy by including autistic trait dimensions, anxiety, and alexithymia.

The Comprehensive Autistic Trait Inventory (CATI): development and validation of a new measure of autistic traits in the general population

BACKGROUND

Traits and characteristics qualitatively similar to those seen in diagnosed autism spectrum disorder can be found to varying degrees in the general population. To measure these traits and facilitate their use in autism research, several questionnaires have been developed that provide broad measures of autistic traits [e.g. Autism-Spectrum Quotient (AQ), Broad Autism Phenotype Questionnaire (BAPQ)]. However, since their development, our understanding of autism has grown considerably, and it is arguable that existing measures do not provide an ideal representation of the trait dimensions currently associated with autism. Our aim was to create a new measure of autistic traits that reflects our current understanding of autism, the Comprehensive Autism Trait Inventory (CATI).

METHODS

In Study 1, 107 pilot items were administered to 1119 individuals in the general population and exploratory factor analysis of responses used to create the 42-item CATI comprising six subscales: Social Interactions, Communication, Social Camouflage, Repetitive Behaviours, Cognitive Rigidity, and Sensory Sensitivity. In Study 2, the CATI was administered to 1068 new individuals and confirmatory factor analysis used to verify the factor structure. The AQ and BAPQ were administered to validate the CATI, and additional autistic participants were recruited to compare the predictive ability of the measures. In Study 3, to validate the CATI subscales, the CATI was administered to 195 new individuals along with existing valid measures qualitatively similar to each CATI subscale.

RESULTS

The CATI showed convergent validity at both the total-scale (r ≥ .79) and subscale level (r ≥ .68). The CATI also showed superior internal reliability for total-scale scores (α = .95) relative to the AQ (α = .90) and BAPQ (α = .94), consistently high reliability for subscales (α > .81), greater predictive ability for classifying autism (Youden's Index = .62 vs .56-.59), and demonstrated measurement invariance for sex.

LIMITATIONS

Analyses of predictive ability for classifying autism depended upon self-reported diagnosis or identification of autism. The autistic sample was not large enough to test measurement invariance of autism diagnosis.

CONCLUSIONS

The CATI is a reliable and economical new measure that provides observations across a wide range of trait dimensions associated with autism, potentially precluding the need to administer multiple measures, and to our knowledge, the CATI is also the first broad measure of autistic traits to have dedicated subscales for social camouflage and sensory sensitivity.

Expression Recognition Difficulty Is Associated with Social But Not Attention-to-Detail Autistic Traits and Reflects Both Alexithymia and Perceptual Difficulty

Autistic people often show difficulty with facial expression recognition. However, the degree of difficulty varies widely, which might reflect varying symptom profiles. We examined three domains of autistic traits in the typical population and found that more autistic-like social skills were associated with greater difficulty labelling expressions, and more autistic-like communication was associated with greater difficulty labelling and perceptually discriminating between expressions. There were no associations with autistic-like attention to detail. We also found that labelling, but not perceptual, difficulty was mediated by alexithymia. We found no evidence that labelling or perceptual difficulty was mediated by weakened adaptive coding. Results suggest expression recognition varies between the sub-clinical expressions of autistic symptom domains and reflects both co-occurring alexithymia and perceptual difficulty.

Sex-specific variation in facial masculinity/femininity associated with autistic traits in the general population

Reports linking prenatal testosterone exposure to autistic traits and to a masculinized face structure have motivated research investigating whether autism is associated with facial masculinization. This association has been reported with greater consistency for females than for males, in studies comparing groups with high and low levels of autistic traits. In the present study, we conducted two experiments to examine facial masculinity/femininity in 151 neurotypical adults selected for either low, mid-range, or high levels of autistic traits. In the first experiment, their three-dimensional facial photographs were subjectively rated by 41 raters for masculinity/femininity and were objectively analysed. In the second experiment, we generated 6-face composite images, which were rated by another 36 raters. Across both experiments, findings were consistent for ratings of photographs and composite images. For females, a linear relationship was observed where femininity ratings decreased as a function of higher levels of autistic traits. For males, we found a U-shaped function where males with mid-range levels of traits were rated lowest on masculinity. Objective facial analyses revealed that higher levels of autistic traits were associated with less feminine facial structures in females and less masculine structures in males. These results suggest sex-specific relationships between autistic traits and facial masculinity/femininity.

Revisiting the overlap between autistic and schizotypal traits in the non-clinical population using meta-analysis and network analysis

The present study aimed to explore the relationship between autistic and schizotypal traits in the non-clinical population. We first conducted a meta-analysis to quantify the correlation between self-reported autistic traits and the three dimensions of schizotypal traits (positive, negative and disorganization). The strongest correlation was found between autistic traits and negative schizotypal traits (r = 0.536, 95% CI [0.481, 0.586]), followed by the disorganization (r = 0.355, 95% CI [0.304, 0.404]) and positive (r = 0.256, 95% CI [0.208, 0.302]) dimensions. To visualize the partial correlations between dimensional behavioural traits, we constructed a network model based on a large sample of college students (N = 2469). Negative schizotypal traits were strongly correlated with autistic social/communicative deficits, whereas positive schizotypal traits were inversely correlated with autistic-like traits, lending support to the psychosis-autism diametrical model. Disentangling the overlapping and diametrical structure of autism and schizophrenia may help to elucidate the aetiology of these two neurodevelopmental disorders.

A comprehensive psychometric analysis of autism-spectrum quotient factor models using two large samples: Model recommendations and the influence of divergent traits on total-scale scores

The Autism-Spectrum Quotient (AQ) is a psychometric scale that is commonly used to assess autistic-like traits and behaviors expressed by neurotypical individuals. A potential strength of the AQ is that it provides subscale scores that are specific to certain dimensions associated with autism such as social difficulty and restricted interests. However, multiple psychometric evaluations of the AQ have led to substantial disagreement as to how many factors exist in the scale, and how these factors are defined. These challenges have been exacerbated by limitations in study designs, such as insufficient sample sizes as well as a reliance on Pearson, rather than polychoric, correlations. In addition, several proposed models of the AQ suggest that some factors are uncorrelated, or negatively correlated, which has ramifications for whether total-scale scores are meaningfully interpretable-an issue not raised by previous work. The aims of the current study were to provide: (a) guidance as to which models of the AQ are viable for research purposes, and (b) evidence as to whether total-scale scores are adequately interpretable for research purposes. We conducted a comprehensive series of confirmatory factor analyses on 11 competing AQ models using two large samples drawn from an undergraduate population (n = 1,702) and the general population (n = 1,280). Psychometric evidence largely supported using the three-factor model described by Russell-Smith et al. [Personality and Individual Differences 51(2), 128-132 (2011)], but did not support the use of total-scale scores. We recommend that researchers consider using AQ subscale scores instead of total-scale scores. Autism Res 2020, 13: 45-60. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: We examined 11 different ways of scoring subscales in the popular Autism-Spectrum Quotient (AQ) questionnaire in two large samples of participants (i.e., general population and undergraduate students). We found that a three-subscale model that used "Social Skill," "Patterns/Details," and "Communication/Mindreading" subscales was the best way to examine specific types of autistic traits in the AQ. We also found some weak associations between the three subscales-for example, being high on the "Patterns/Details" subscale was not predictive of scores on the other subscales. This means that meaningful interpretation of overall scores on the AQ is limited.

Exploring the Extent in the Visual Field of the Honeycomb and Extinction Illusions

There are situations in which what is perceived in central vision is different to what is perceived in the periphery, even though the stimulus display is uniform. Here, we studied two cases, known as the Extinction illusion and the Honeycomb illusion, involving small disks and lines, respectively, presented over a large extent of the visual field. Disks and lines are visible in the periphery on their own, but they become invisible when they are presented as part of a pattern (grid). Observers (N = 56) adjusted a circular probe to report the size of the region in which they had seen the lines or the disks. Different images had black or white lines/disks, and we included control stimuli in which these features were spatially separated from the regular grid of squares. We confirmed that the illusion was experienced by the majority of observers and is dependent on the interaction between the elements (i.e., the lines/disks have to be near the squares). We found a dissociation between the two illusions in the dependence on contrast polarity suggesting different mechanisms. We analysed the variability between individuals with respect to schizotypical and autistic-spectrum traits (short version of the Oxford-Liverpool Inventory of Feelings and Experiences [O-LIFE] questionnaire and the Autistic Quotient, respectively) but found no significant relationships. We discuss how illusions relative to what observers are aware of in the periphery may offer a unique tool to study visual awareness.

A Transdiagnostic Perspective on Social Anhedonia

Humans are highly social beings, yet people with social anhedonia experience reduced interest in or reward from social situations. Social anhedonia is a key facet of schizotypal personality, an important symptom of schizophrenia, and increasingly recognized as an important feature in a range of other psychological disorders. However, to date, there has been little examination of the similarities and differences in social anhedonia across diagnostic borders. Here, our goal was to conduct a selective review of social anhedonia in different psychological and life course contexts, including the psychosis continuum, depressive disorder, posttraumatic stress disorder, eating disorders, and autism spectrum disorders, along with developmental and neurobiological factors. Current evidence suggests that the nature and expression of social anhedonia vary across psychological disorders with some groups showing deficient learning about, enjoyment from, and anticipation of the pleasurable aspects of social interactions, while for others, some of these components appear to remain intact. However, study designs and methodologies are diverse, the roles of developmental and neurobiological factors are not routinely considered, and direct comparisons between diagnostic groups are rare-which prevents a more nuanced understanding of the underlying mechanisms involved. Future studies, parsing the wanting, liking, and learning components of social reward, will help to fill gaps in the current knowledge base. Consistent across disorders is diminished pleasure from social situations, subsequent withdrawal, and poorer social functioning in those who express social anhedonia. Nonetheless, feelings of loneliness often remain, which suggests the need for social connection is not entirely absent. Adolescence is a particularly important period of social and neural development and may provide a valuable window on the developmental origins of social anhedonia. Adaptive social functioning is key to recovery from mental health disorders; therefore, understanding the intricacies of social anhedonia will help to inform treatment and prevention strategies for a range of diagnostic categories.

Negatively phrased items of the Autism Spectrum Quotient function differently for groups with and without autism

The Autism Spectrum Quotient is a widely used instrument for the detection of autistic traits. However, the validity of comparisons of Autism Spectrum Quotient scores between groups may be threatened by differential item functioning. Differential item functioning entails a bias in items, where participants with equal values of the latent trait give different answers because of their group membership. In this article, items of the Autism Spectrum Quotient were studied for differential item functioning between different groups within a single sample (N = 408). Three analyses were conducted. First, using a Rasch mixture model, two latent groups were detected that show differential item functioning. Second, using a Rasch regression tree model, four groups were found that show differential item functioning: men without autism, women without autism, people 50 years and younger with autism, and people older than 50 years with autism. Third, using traditional methods, differential item functioning was detected between groups with and without autism. Therefore, group comparisons with the Autism Spectrum Quotient are at risk of being affected by bias. Eight items emerged that consistently show differences in response tendencies between groups across analyses, and these items were generally negatively phrased. Two often-used short forms of the Autism Spectrum Quotient, the AQ-28 and AQ-10, may be more suitable for group comparisons.

Cluster analysis reveals subclinical subgroups with shared autistic and schizotypal traits

Autism and schizophrenia spectrum research is typically based on coarse diagnostic classification, which overlooks individual variation within clinical groups. This method limits the identification of underlying cognitive, genetic and neural correlates of specific symptom dimensions. This study, therefore, aimed to identify homogenous subclinical subgroups of specific autistic and schizotypal traits dimensions, that may be utilised to establish more effective diagnostic and treatment practices. Latent profile analysis of subscale scores derived from an autism-schizotypy questionnaire, completed by 1678 subclinical adults aged 18-40 years (1250 females), identified a local optimum of eight population clusters: High, Moderate and Low Psychosocial Difficulties; High, Moderate and Low Autism-Schizotypy; High Psychosis-Proneness; and Moderate Schizotypy. These subgroups represent the convergent and discriminant dimensions of autism and schizotypy in the subclinical population, and highlight the importance of examining subgroups of specific symptom characteristics across these spectra in order to identify the underlying genetic and neural correlates that can be utilised to advance diagnostic and treatment practices.

Childhood trauma is not a confounder of the overlap between autistic and schizotypal traits: A study in a non-clinical adult sample

Childhood trauma has been shown to be a robust risk factor for mental disorders, and may exacerbate schizotypal traits or contribute to autistic trait severity. However, little is known whether childhood trauma confounds the overlap between schizotypal traits and autistic traits. This study examined whether childhood trauma acts as a confounding variable in the overlap between autistic and schizotypal traits in a large non-clinical adult sample. A total of 2469 participants completed the Autism Spectrum Quotient (AQ), the Schizotypal Personality Questionnaire (SPQ), and the Childhood Trauma Questionnaire-Short Form. Correlation analysis showed that the majority of associations between AQ variables and SPQ variables were significant (p < 0.05). In the multiple regression models predicting scores on the AQ total, scores on the three SPQ subscales were significant predictors(Ps < 0.05). Scores on the Positive schizotypy and Negative schizotypy subscales were significant predictors in the multiple regression model predicting scores on the AQ Social Skill, AQ Attention Switching, AQ Attention to Detail, AQ Communication, and AQ Imagination subscales. The association between autistic and schizotypal traits could not be explained by shared variance in terms of exposure to childhood trauma. The findings point to important overlaps in the conceptualization of ASD and SSD, independent of childhood trauma.

Glutamate/GABA+ ratio is associated with the psychosocial domain of autistic and schizotypal traits

BACKGROUND

The autism and schizophrenia spectra overlap to a large degree in the social and interpersonal domains. Similarly, abnormal excitatory glutamate and inhibitory γ-aminobutyric acid (GABA) neurotransmitter concentrations have been reported for both spectra, with the interplay of these neurotransmitters important for cortical excitation to inhibition regulation. This study investigates whether these neurotransmitter abnormalities are specific to the shared symptomatology, and whether the degree of abnormality increases with increasing symptom severity. Hence, the relationship between the glutamate/GABA ratio and autism and schizophrenia spectrum traits in an unmedicated, subclinical population was investigated.

METHODS

A total of 37 adults (19 female, 18 male) aged 18-38 years completed the Autism Spectrum Quotient (AQ) and Schizotypal Personality Questionnaire (SPQ), and participated in the resting state proton magnetic resonance spectroscopy study in which sequences specific for quantification of glutamate and GABA+ concentration were applied to a right and left superior temporal voxel.

RESULTS

There were significant, moderate, positive relationships between right superior temporal glutamate/GABA+ ratio and AQ, SPQ and AQ+SPQ total scores (p<0.05), SPQ subscales Social Anxiety, No Close Friend, Constricted Affect, Odd Behaviour, Odd Speech, Ideas of Reference and Suspiciousness, and AQ subscales Social Skills, Communication and Attention Switching (p<0.05); increased glutamate/GABA+ coinciding with higher scores on these subscales. Only the relationships between glutamate/GABA+ ratio and Social Anxiety, Constricted Affect, Social Skills and Communication survived multiple comparison correction (p< 0.004). Left superior temporal glutamate/GABA+ ratio reduced with increasing restricted imagination (p<0.05).

CONCLUSION

These findings demonstrate evidence for an association between excitatory/inhibitory neurotransmitter concentrations and symptoms that are shared between the autism and schizophrenia spectra.

Co-occurrence of autistic and schizotypal traits and its association with emotional and psychosocial function in Chinese college students

Empirical findings suggest an overlap between autism spectrum disorders (ASD) and schizophrenia spectrum disorders (SSD). Co-occurring autistic and positive schizotypal traits may have a moderating effect on behaviour and cognition. This study attempted to examine the co-occurrence rate of autistic and schizotypal traits in otherwise healthy college students and to test the moderating effect of co-occurring autistic and schizotypal traits on executive function, emotion processing and social function. Eight hundred and sixty-four participants took part in the present study. The results showed that the co-occurrence rate of autistic and schizotypal trait was 3.4% at baseline and 2.4% at one-year follow-up. The interaction between autistic traits and schizotypal traits was associated with better executive functioning and social functioning but poorer emotional expression.

Validation of the French Autism Spectrum Quotient scale and its relationships with schizotypy and Eysenckian personality traits

BACKGROUND

Autism and schizophrenia spectra were long considered distinct entities. Yet, recent studies emphasized overlapping clinical and personality features suggesting common mechanisms and liabilities. Independent notions, however, highlight that the two spectra oppose each other socially (positive schizotypal hyper-mentalism versus autistic hypo-mentalism).

METHODS

To clarify these relationships, we used data from 921 French-speaking Swiss undergraduates to firstly validate the French Autism Spectrum Questionnaire (AQ) identifying an optimal factor structure. Secondly, we assessed relationships between this AQ structure and schizotypic personality traits.

RESULTS

Results from correlational and principal component analyses replicated both overlapping and opposing relationships.

CONCLUSIONS

We conjecture that autistic traits opposing positive schizotypy represent autistic mentalizing deficits. We discuss implications of our findings relative to theories of autism and schizophrenia spectrum relationships.

Hedonic Capacity in the Broader Autism Phenotype: Should Social Anhedonia Be Considered a Characteristic Feature?

Impairments in social motivational processes may partially explain the differences in social interaction seen among individuals with autism spectrum disorder (ASD). The social motivation hypothesis would predict an association between reduced hedonic capacity and ASD. However, to date, findings have been mixed regarding hedonic deficits among individuals with ASD; adults report lower levels of both social and physical pleasure whereas adolescents only report experiencing lower social pleasure. Moreover, very few studies examining the association between anhedonia and autistic traits have used measures of hedonic response or taken temporal aspects of pleasure into account. The present study examined associations between autistic traits and the experience of pleasure using a non-clinical sample of young adults to further clarify the nature of hedonic deficits in the broader autism phenotype (BAP). Results revealed that autistic traits were negatively associated with both the experience of social pleasure as well as general pleasure, although the association was stronger for social pleasure. Regression analyses revealed that reduced social pleasure was a better predictor of autistic traits than general pleasure. Together these findings suggest that reduced social hedonic capacity is associated with autistic traits in the general population and should be included in conceptualizations of the BAP.

Psychopathological traits in college students from top-ranking french schools: Do autistic features impair success in science when associated with schizotypal traits?

The link between personality and the interest of individuals for science has not been thoroughly explored. In this report, we studied psychopathological traits in students studying science in French top-ranking institutions. Three hundred and forty seven individuals answered questionnaires assessing autistic and schizotypal dimensions, as well as anxiety, depression symptomatology and attachment quality. A cluster analysis based on autistic and schizotypal traits led to the identification of 4 distinct profiles: a "low trait cluster", a "moderate autistic trait cluster", a "moderate schizotypal trait cluster" and a "high trait cluster" (HTC) composed of individuals with high scores on both autistic and schizotypal scales. Each cluster represented 20.1-27.1% of participants and was clearly different from the three others, both on autistic and on schizotypal dimensions. These groups could be also typified by their level of anxiety, depression or degraded attachment, which are proportional to the extent of psychopathological traits. Moreover, students from the HTC cluster displayed lower academic results, thus implying that autistic traits might impair success in science when they are associated with moderate schizotypal personality features. This study also suggests that depression and anxiety might mediate performance inhibition in the HTC group.

Do the Autism Spectrum Quotient (AQ) and Autism Spectrum Quotient Short Form (AQ-S) Primarily Reflect General ASD Traits or Specific ASD Traits? A Bi-Factor Analysis

In the current study, we fit confirmatory bi-factor models to the items of the Autism Spectrum Quotient (AQ) and Autism Spectrum Quotient Short Form (AQ-S) in order to assess the extents to which the items of each reflect general versus specific factors. The models were fit in a combined sample of individuals with and without a clinical diagnosis of autism spectrum disorders. Results indicated that, with the exception of the Attention to Details factor in the AQ and the Numbers/Patterns factors in the AQ-S, items primarily reflected a general factor. This suggests that when attempting to estimate an association between a specific symptom measured by the AQ or AQ-S and some criterion, associations will be confounded by the general factor. To resolve this, we recommend using a bi-factor measurement model or factor scores from a bi-factor measurement whenever hypotheses about specific symptoms are being assessed.

MACROD2 gene associated with autistic-like traits in a general population sample

There is now substantial evidence that autistic-like traits in the general population lie on a continuum, with clinical autism spectrum disorders (ASD) representing the extreme end of this distribution. In this study, we sought to evaluate five independently identified genetic associations with ASD with autistic-like traits in the general population. In the study cohort, clinical phenotype and genomewide association genotype data were obtained from the Western Australian Pregnancy Cohort (Raine) Study. The outcome measure used was the Autism Spectrum Quotient (AQ), a quantitative measure of autistic-like traits of individuals in the cohort. Total AQ scores were calculated for each individual, as well as scores for three subscales. Five candidate single nucleotide polymorphism (SNP) associations with ASD, reported in previously published genomewide association studies, were selected using a nominal cutoff value of P less than 1.0×10. We tested whether these five SNPs were associated with total AQ and the subscales, after adjustment for possible confounders. SNP rs4141463 located in the macro domain containing 2 (MACROD2) gene was significantly associated with the Communication/Mindreading subscale. No other SNP was significantly associated with total AQ or the subscales. The MACROD2 gene is a strong positional candidate risk factor for autistic-like traits in the general population.

The perinatal androgen to estrogen ratio and autistic-like traits in the general population: a longitudinal pregnancy cohort study

BACKGROUND

Prenatal androgen exposure has been hypothesized to be linked to autism spectrum disorder (ASD). While previous studies have found a link between testosterone levels in amniotic fluid and autistic-like traits, a similar relationship has not been found for testosterone in umbilical cord blood. However, it may be the net biological activity of multiple androgens and estrogens that influences postnatal effects of prenatal sex steroids. Accordingly, composite levels of androgens (A) and estrogens (E) were investigated, along with their ratio, in relation to autistic-like traits in young adulthood.

METHODS

Sex steroid data in umbilical cord blood were available from 860 individuals at delivery. Samples were analyzed for androgens (testosterone, androstenedione, and dehydroepiandrosterone) and estrogens (estrone, estradiol, estriol, and estetrol). Levels of bioavailable testosterone, estradiol, and estrone were measured and used to calculate A and E composites and the A to E ratio. Participants were approached in early adulthood to complete the autism-spectrum quotient (AQ) as a self-report measure of autistic-like traits, with 183 males (M = 20.10 years, SD = 0.65 years) and 189 females (M =19.92 years, SD = 0.68 years) providing data.

RESULTS

Males exhibited significantly higher androgen composites and A to E composite ratios than females. Males also scored significantly higher on the details/patterns subscale of the AQ. Subsequent categorical and continuous analyses, which accounted for covariates, revealed no substantial relationships between the A/E composites or the A to E ratio and the AQ total or subscale scores.

CONCLUSIONS

The current study found no link between the A/E composites or the A to E ratio in cord blood and autistic-like traits in the population as measured by the AQ. These outcomes do not exclude the possibility that these sex steroid variables may predict other neurodevelopmental traits in early development.

Asperger syndrome and schizophrenia: Overlap of self-reported autistic traits using the Autism-spectrum Quotient (AQ)

BACKGROUND

In clinical practice, the differential diagnosis of Asperger syndrome (AS) versus schizophrenia can be a challenge. Some self-report instruments-such as the Autism-spectrum Quotient (AQ)-have been portrayed as proxies for the diagnosis of AS. However, it has not been demonstrated to what extent autistic traits-as measured by the AQ-separate AS from schizophrenia.

AIM

To examine the AS-schizophrenia discriminating ability of the AQ.

METHOD

The AQ is a 50-item self-administered questionnaire (with score range 0-50) for measuring "autistic traits" in adults. Here, it was completed by 136 individuals: 36 with schizophrenic psychosis, 51 with AS and 49 non-clinical comparison cases. A receiver operating characteristic (ROC) analysis for the total AQ score was performed to examine the discriminating power of the instrument.

RESULT

Both individuals with schizophrenia and individuals with AS scored significantly higher on AQ than the non-clinical group. The mean total AQ score (± standard deviation) of the AS group (26.7 ± 8.9; range 9-44) was significantly higher than that of the schizophrenia group (22.7 ± 6.2; range 10-35) (P = 0.041). However, when using the full Likert scale for scoring, the difference did not reach significance. In the ROC analysis of total AQ scores for AS versus schizophrenia, the area under the curve (AUC) was 0.65 (P = 0.02).

CONCLUSION

Although mean AQ scores separated AS and schizophrenia at a group comparison level, significant overlap of AQ scores across the two diagnostic groups clearly reduces the discriminating power of the AQ in the separation of schizophrenia from AS.

Sexually dimorphic facial features vary according to level of autistic-like traits in the general population

BACKGROUND

In a recent study, Bejerot et al. observed that several physical features (including faces) of individuals with an autism spectrum disorder (ASD) were more androgynous than those of their typically developed counterparts, suggesting that ASD may be understood as a 'gender defiant' disorder. These findings are difficult to reconcile with the hypermasculinisation account, which proposes that ASD may be an exaggerated form of cognitive and biological masculinity. The current study extended these data by first identifying six facial features that best distinguished males and females from the general population and then examining these features in typically developing groups selected for high and low levels of autistic-like traits.

METHODS

In study 1, three-dimensional (3D) facial images were collected from 208 young adult males and females recruited from the general population. Twenty-three facial distances were measured from these images and a gender classification and scoring algorithm was employed to identify a set of six facial features that most effectively distinguished male from female faces. In study 2, measurements of these six features were compared for groups of young adults selected for high (n = 46) or low (n = 66) levels of autistic-like traits.

RESULTS

For each sex, four of the six sexually dimorphic facial distances significantly differentiated participants with high levels of autistic-like traits from those with low trait levels. All four features were less masculinised for high-trait males compared to low-trait males. Three of four features were less feminised for high-trait females compared to low-trait females. One feature was, however, not consistent with the general pattern of findings and was more feminised among females who reported more autistic-like traits. Based on the four significantly different facial distances for each sex, discriminant function analysis correctly classified 89.7% of the males and 88.9% of the females into their respective high- and low-trait groups.

CONCLUSIONS

The current data provide support for Bejerot et al.'s androgyny account since males and females with high levels of autistic-like traits generally showed less sex-typical facial features than individuals with low levels of autistic-like traits.

Investigating the role of alexithymia on the empathic deficits found in schizotypy and autism spectrum traits

Alexithymia, the inability to identify and describe one's emotional experience, is elevated in many clinical populations, and related to poor interpersonal functioning. Alexithymia is also associated with empathic deficits in individuals with autism spectrum disorders. Accordingly, a better understanding of alexithymia could elucidate the nature of social-cognitive deficits transdiagnostically. We investigated alexithymia and components of empathy in relation to schizotypal and autism spectrum traits in healthy college students. Specifically, we examined higher-order components of empathic processing that involve perspective taking and other-oriented concern, which are reduced in alexithymia. Higher-order empathic processing was inversely correlated with both schizotypal and autism spectrum traits. Bootstrapping techniques revealed that alexithymia had a significant indirect effect on the relationship between higher-order empathy and these personality traits; thus, alexithymia contributes uniquely to their relationship. These findings suggest alexithymia represents one possible mechanism for the development of empathic deficits in these populations. These results are consistent with the perspective that awareness of one's own emotional state may predicate a successful empathic response to another's. This work highlights the importance of a consideration of alexithymia in elucidating the nature of empathic deficits in various clinical populations, and points to a potential point of social intervention.

Factor Analysis Demonstrates a Common Schizoidal Phenotype within Autistic and Schizotypal Tendency: Implications for Neuroscientific Studies

Behavioral and cognitive dysfunction, particularly social and communication impairments, are shared between autism and schizophrenia spectrum disorders, while evidence for a diametric autism-positive schizophrenia symptom profile is inconsistent. We investigated the shared phenotype at a personality trait level, particularly its resemblance to schizoid personality disorder, as well as differential aspects of the autism-schizophrenia model. Items of the autism spectrum quotient (AQ) and schizotypal personality questionnaire (SPQ) were pseudo-randomly combined, and were completed by 449 (162 male, 287 female) non-clinical participants aged 18-40. A factor analysis revealed three factors; the first represented a shared social disorganization phenotype, the second reflected perceptual oddities specific to schizotypy while the third reflected social rigidity specific to autism. The AQ and SPQ were strongly correlated with Factor 1 (AQ: r = 0.75, p < 0.001; SPQ: r = 0.96, p < 0.001), SPQ score was correlated with Factor 2 (r = 0.51, p < 0.001), particularly in cognitive-perceptual features (r = 0.66, p < 0.001), and AQ score was strongly correlated with Factor 3 (r = 0.76, p < 0.001). Furthermore, there was no relationship between Factor 1 and Factor 2. Thus, there is robust evidence for a shared social disorganization phenotype in autistic and schizotypal tendency, which reflects the schizoid phenotype. Discriminating and independent dimensions of schizotypal and autistic tendency exist in Factors 2 and 3, respectively. Current diagnostic protocols could result in different diagnoses depending on the instrument used, suggesting the need for neuromarkers that objectively differentiate autistic and schizotypal traits and resolve the question of commonality versus co-morbidity.

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.