Master Thesis Clinical Neuropsychology
Overlap between autistic traits and schizotypy traits - the association with
executive functions, personality and feeling different.
Katarzyna Migut
Studentnummer: 5610613
Supervisor / Eerste beoordelaar: dr. Annemie Ploeger Tweede beoordelaar: dr. M de Vries
20 Juni 2014
Universitetit van Amsterdam
Abstract
Over the past years several studies have attempted to assess if there is an overlap between autistic and schizotypy traits, both in the clinical and in the general population.
Substantial evidence for this overlap has been found, however the precise relationship between autistic and schizotypy traits is still not known. To contribute to the understanding of the nature of this overlap we introduce a new "feeling different from other people" variable and examine how it correlates with autistic and schizotypy traits. To explore the association between those traits in the general population, autistic traits were measured using AQ – short, schizotypy traits were measured using O-LIFE – short. Furthermore, BRIEF-A was used to assess executive functions, QBF to measure personality traits and our novel questionnaire “Feeling
Different”.Significant correlation was found between autistic and schizotypy traits. Both traits were significantly associated with executive functions, extraversion, neuroticism and feeling different. Also autistic traits and schizotypy traits were predicted by executive functions, extraversion, neuroticism and feeling different.
Results support earlier findings of overlap between autistic and schizotypy traits. Moreover, our novel findings of association between feeling different, executive functions, personality, and autistic and schizotypy traits are promising and advocate further investigation of the nature of this association.
Contents
1. Introduction ... 5
1.1. Autism ... 5
1.2. Schizophrenia ... 6
1.3. Overlap between autism and schizophrenia ... 6
1.3.1. Symptoms ... 6
1.3.2. Genetics ... 7
1.3.3. Neuropathology ... 7
1.3.4. Minor physical anomalies ... 8
1.3.5. Cognitive domains ... 8
1.4. Overlap between autistic traits and schizotypy traits ... 10
1.5. Current research and the “feeling different” concept ... 10 Part I “Feeling different“ 2. Introduction ... 13 3. Materials and methods ... 15 3.1. Participants ... 16
3.2. Feeling Different Questionnaire (FD) ... 16
3.3. Procedure ... 17 4. Results ... 17
5. Discussion ... 20
Part II “Overlap between autistic traits and schizotypy traits” 6. Materials and methods ... 21
6.1. Participants ... 21
6.2 Materials ... 21
6.2.1. Autism Spectrum Questionnaire short (AQ short) ... 21
6.2.2. Oxford-Liverpool Inventory of Feelings and Experience short (O-LIFE short) ... 22
6.2.3. Quick Big Five (QBF) ... 22
6.2.4. Behavioral Rating Inventory of Executive Function Adults (BRIEF - A) ... 23
6.2.5. Feeling Different questionnaire ... 24
6.3. Procedure ... 25
6.4. Statistical analysis ... 25 7. Results ... 26 7.1 Descriptive statistics ... 26
7.2. Autistic traits and schizotypy traits ... 28
7.2.1. Autistic traits and feeling different. ... 29
7.2.2. Autistic traits and executive functions ... 30
7.2.3. Autistic traits and personality traits ... 31
7.3.1.Schizotypy traits and feeling different ... 32
7.3.2. Schizotypy traits and executive functions ... 33
7.3.3. Schizotypy traits and personality traits ... 34
7.3.4. Executive functions, personality and feeling different... 34
8. Discussion and conclusion ... 36
8.1. Limitations ... 39
9. References ... 41
Appendix 1. First version of Feeling Different questionnaire ... 52
Appendix 2. Final version of Feeling Different questionnaire ... 56
Appendix 3. Factor loadings of 13 components of Feeling different questionnaire ... 59
1. Introduction
There is substantial evidence that there is an overlap between autistic traits and schizotypy traits in the general population (Russell-Smith, Maybery and Bayliss, 2011; Hurst, Nelson-Gray, Mitchell and Kwapil, 2007; Dinsdale, Hurd, Wakabayashi, Elliot and Crespi, 2013). With regard to the clinical population, overlap between autism and schizophrenia is also found (Raja and Azzoni, 2010; Barneveld, Pieterse, de Sonneville, Van Rijn, Lahuis, Van Engeland and colleagues, 2011), however the precise relationship is still not known.
Autism spectrum disorders and schizophrenia spectrum disorders are multidimensional neurodevelopmental disorders, both considered to emerge in early embryogenesis (Ploeger, Raijmakers, van der Maas and Galis, 2010). The diagnosis of both disorders is based on the presence of specific symptoms.
The aim of this study was to explore if there is an association between autistic traits, schizotypy traits and a newly introduced variable “feeling different”. Also the association between autistic traits, schizotypy traits and other personality traits as well as the association of those traits with the executive functioning was assessed.
1.1. Autism
The diagnosis of autism spectrum disorder (ASD) is based on the presence of deficits in social communication and the presence of excessively repetitive behaviors, restricted interests, and insistence on sameness (Diagnostic and Statistical Manual of Mental Disorders-V (DSM-V), American Psychiatric Association (APA), 2013). The prevalence of ASD is about 60 per 10,000
(Fombonne et al, 2006) and boys are 4.3 times more likely to be affected than girls (Fombonne, 2005). The heritability of autism varies from 0.7 to 0.9 (Geschwind, 2009).
1.2. Schizophrenia
Schizophrenia spectrum and other psychotic disorders include schizophrenia, other psychotic disorders, and schizotypal (personality) disorder. They are defined by abnormalities in one or more of the following five domains: delusions, hallucinations, disorganized thinking (speech), grossly disorganized or abnormal motor behavior (including catatonia), and negative symptoms (avolition, flat affect and anhedonia) (DSM-V, APA, 2013). The prevalence of schizophrenia ranges from 1.4 – 1.6 per 1000 (Nylander, Lugnenagrd and Hallerback, 2008). No gender differences are found in the prevalence of schizophrenia in epidemiological studies (Ochoa, Usall, Cobo, Labad and Kulkarni 2012). The heritability of schizophrenia is estimated to be 0.8 (Van Os, Linscott, Myin-Germeys, Delespaul and Krabbendam, 2009).
1.3. Overlap between autism and schizophrenia
The overlap between autism and schizophrenia is observed in different domains, such as
symptoms, genetics, neuropathology, minor physical anomalies and cognitive functioning. In the following paragraphs few examples are given to illustrate the significance of this overlap.
1.3.1. Symptoms
When assessing the overlap of the symptoms, it seems that some non-psychotic symptoms and signs in schizophrenia might overlap with those of autism (Nylander et al., 2008). The overlap is most apparent with regard to negative symptoms of schizophrenia, which are avolition,
anhedonia and flat affect (Hurst et al. 2007). The overlap is also found in following domains: disorganization, attention to detail and imagination (Spek and Wouters, 2010). However, it is worth mentioning that positive symptoms such as delusions and hallucinations are difficult to assess in patients with more severe forms of autism and therefore might not be observed in those severe cases (Konstantareas and Hewit, 2001).
1.3.2. Genetics
Results of many genetic research (Rapoport, Chavez, Greenstein, Addington and Gogtay, 2009; Burbach 2009; Raja and Azzoni, 2010) indicate that there is genetic overlap between autism and schizophrenia. Vero-cardiofacial deletion syndrome (chromosome 22q11.2) (Rapoport et al., 2009; Antshel, Aneja, Strunge, Peebles, Fremont, Stallone and colleagues, 2007), abnormalities of single nucleotide polymorphism (SNP) of DISC1 gene (Kilpinen, Ylisaukko-oja, Hennah, Palo, Varilo, Vanhala et al., 2008; Rapoport et al., 2009) and deletions, disruptions and missense mutations in Neurexin1 (Rapoport, 2009) are often reported. Recently it was established that 13,8% of copy number variants found in autism spectrum disorders showed overlap with schizophrenia and 15,3 % of copy number variants found in schizophrenia showed overlap with autism spectrum disorders (Vortsman and Burbach, 2014). Recently also mutations in the Gephyrin (GPHN) gene at 14q23.3 are implicated in genetic risk for autism spectrum disorders and schizophrenia (Lionel, Vaags, Sato, Gazzellone, Mitchell, Chen and colleagues, 2013).
1.3.3. Neuropathology
Additional evidence for the overlap between schizophrenia spectrum disorders and autism
spectrum disorders comes from anatomical studies. Zhan, Paolicelli, Sforazzini, Weinhard, Bolasco, Pagani, and colleagues (2014) reported that deficits in microglia-dependent synaptic pruning induce weak functional connectivity in both autism and schizophrenia.
Shared neuropathology between autism and schizophrenia is also supported by research on mirror neurons. Using Transcranial Magnetic Stimulation it has been shown that the activation patterns of mirror neurons might be abnormal in autism and schizophrenia (Oberman, Hubbard, McCleery, Altschuler, Ramachandran, and Pineda, 2005; Bertrand, Achim, Harvey, Sutton, Malla and Lepage, 2008).
Also migrational defects such as an abnormally high number of superficial subcortical Reelin-deficient interstitial white matter neurons are apparent in autism and schizophrenia (Lacy and King, 2013).
1.3.4. Minor physical anomalies
In the past years minor physical anomalies became associated with both autism and schizophrenia (Tripi et al., 2008; Aksoy-Poyraz, Poyraz, Turan and Aikan, 2011). Minor physical anomalies (MPAs) are easily detectable morphological abnormalities. They have no (serious) medical consequences (Ozgen, Hop, Beemer and van Engeland, 2010). They can indicate maldevelopment (Sivkov and Akabaliev, 2003) and include slight dysmorphic features such as low-seated ears or a horizontal crease in the hand-palm. Of great importance are MPAs found in ectodermal derivates (e.g. skin, hair, ears) (Sivkov and Akabaliev, 2003).
1.3.5. Cognitive domains
Besides an overlap in symptoms, genetics and MPAs the overlap between autism spectrum disorders and schizophrenia spectrum disorders is also found in some cognitive domains (Morioka, Kawaike, Sameshima and Ijichi, 2013). Both autism and schizophrenia share deficits in theory of mind (Baron-Cohen, Leslie and Frith, 1985; Lysaker et al. 2010). Schizophrenic patients show difficulties with self-reflectivity (Lysaker et al., 2010) and autistic patients show lack of capacity to form second-order representations, which in turn are needed for the emergence of pretend play (Baron-Cohen et al., 1985).
Impairment in central coherence is apparent in both disorders (Baron-Cohen et al., 1985; Uhlhaas and Silverstein, 2005). Autistic patients exhibit difficulties with extracting global forms and show more detail-focused processing, indicating a weak central coherence (Happe and Frith, 2006). Deficits in perceptual organization are seen in schizophrenic patients with high levels of disorganization (Uhlhaas and Silverstein, 2005).
With regard to executive functioning autistic patients show poor response selection/monitoring on cognitive estimate tasks (Rogers, Viding, Blair, Firth, and Happe, 2006; Hill, 2004). Autistic patients show deficits in planning and mental flexibility where perseverative responses are evident. Deficits in (prepotent) response inhibition are seen as well (Hill, 2004). The impairments in executive functioning are also found in schizophrenic patients (Pickup, 2008; Kravariti, Dixon, Frith, Murray and McGuire, 2005). Schizophrenic patients show deficits in (prepotent) response inhibition as measured by the Colour–Word Score of the Stroop Neuropsychological Screening Test. The response suppression is also impaired (Kravariti et al., 2005).
1.4. Overlap between autistic traits and schizotypy traits
Previous research (Russell-Smith, Maybery and Bayliss, 2011; Russell-Smith, Bayliss and Maybery, 2013) showed that there is an overlap between autistic and schizotypy traits in the general population. This overlap is apparent despite that both types of traits belong to two separate disorder spectra. Recently, Russell-Smith, Bayliss and Maybery (2013) tried to get a better understanding of this overlap. They found that social deficits characteristic in autism spectrum and negative symptoms of schizotypy are both associated with social anxiety, fear of negative evaluation, poor social skills, anhedonia, low mood, and generalized anxiety.
1.5. Current research and the “feeling different” concept
In the present study we will study different variables that may underlie the overlap in autistic and schizotypy traits. This study is the first to assess the relation between these traits and executive functioning in the non-clinical population. In addition, we will study whether there is an association with other personality traits, i.e., the Big Five personality traits. Wakabayashi, Baron-Cohen, and Wheelwright (2006) found that people with autism spectrum conditions are having high neuroticism level, low extraversion level and low conscientiousness level (measured with NEO-PI-R). Schizophrenic patients tend to be more neurotic and introverted than controls (Herran, Sierra-Biddle, Cuesta, Sandoya and Vazquez-Barquero, 2006).
Finally, we will study a variable which we call ‘feeling different from other people’. It is possible that people, who score high on both autistic and schizotypy traits, simply do so because they feel different from other people in general. It was found in the previous research that people who
score high on both autistic and schizotypy traits tend to overestimate their physical anomalies (Veldkamp, 2010, unpublished manuscript). This finding led us to the question whether people with high scores on autistic and schizotypy traits see themselves as being different from other people.
The overlap between autistic and schizotypy traits cannot be simply explained by means of disturbances in early embryogenesis. If it would be the consequence of disturbance in the early embryogenesis then it would be expected that autistic traits and schizotypy traits should be associated with minor physical anomalies (Ploeger, Raijmakers, van der Maas and Galis, 2009). In the general population this is not the case, suggesting that there is another factor associated with autistic and schizotypy traits.
Current research consists of two parts. In Part I we present the rationale behind “feeling
different” concept and the process of construction and validation of the new questionnaire. The focus of Part II was the association between autistic and schizotypy traits. We investigated this association further by exploring the relation between autistic and schizotypy traits, and executive functions, personality and feeling different from other people.
The following hypotheses were tested:
a) There is a positive correlation between autistic traits and schizotypy traits.
b) There is a positive correlation between autistic traits and deficits in executive function. c) There is a positive correlation between schizotypy traits and deficits in executive function. d) There is a positive correlation between autistic traits and neuroticism.
e) There is a negative correlation between autistic traits and extraversion.
f) There is a positive correlation between schizotypy traits and neuroticism. g) There is a negative correlation between schizotypy traits and extraversion.
h) There is a positive correlation between autistic traits and feeling different from other people. i) There is a positive correlation between schizotypy traits and feeling different from other people.
Part I “Feeling different“
2. Introduction
Recently, Russell-Smith and colleagues (2013) reported that social anxiety, fear of negative evaluation, poor social skills, anhedonia, low mood, and generalized anxiety are all associated with social deficits characteristic for autism spectrum disorders and negative symptoms of schizotypy. To further explore the association between autistic and schizotypy traits we propose to broaden that association with the concept of “feeling different from other people”. There is extensive evidence that in both autism spectrum disorders and schizophrenia spectrum disorder several abilities, such as perceiving humor or being creative are expressed differently comparing to a non-clinical population. Therefore we aimed to include all possible aspects of the Feeling Different concept. In the following paragraphs some examples are given to support the Feeling Different concept.
Mood swings. Many autistic children are anhedonic and unhappy. These children are
often frustrated, negative, irritable and withdrawn from social contact. They are anxious and phobic (DeLong, 2004). Also Mazzone and colleagues (2013) found that patients with autism spectrum and high functioning autism display significantly more depressive symptoms than the control group.
With regard to schizotypy traits Fonseca-Pedrero and colleagues (2011) reported a high degree of overlap between schizotypy and depressive symptoms in non-clinical group of adolescents.
Furthermore depression appears to have impact on the severity of functional deficits and cognitive deficits (Iosifescua, 2012).
Being creative. Fink and others (2014) found that schizotypy and creativity are related to
similar brain activity patterns during creative ideation. Positive-schizotypy was found to be associated with generation of creative responses (Burch, Pavelis, Hemsley and Corr, 2006).
Having different skills. Children with autism spectrum disorder display significantly
better abilities on standardized measures of numerical problem solving compared to controls (Iuculano et al., 2013).
Becoming an expert in recognizing repeating patterns in stimuli is a common characteristic of individuals with autism spectrum disorder (Baron-Cohen, Ashwin, Ashwin, Tavassoli and Chakrabarti, 2009).
Sensory abnormalities are found in over 90 per cent of children with autism spectrum disorder. Processing and accurateness in visual and auditory modalities seem to be better in children with ASD compared to controls (Baron-Cohen et al, 2009).
Feeling lonely and not understood. In patients with psychotic disorders loneliness was
found to be a mediator in relationship between stigma and depression (Switaj, Grygiel, Anczewska and Wciórka, 2013).
Locke and colleagues (2010) found that adolescents with autism spectrum disorders report significantly more loneliness in comparison to their typically developing peers.
Different family. In the Asian population it was found that parents of children with
autism spectrum disorder show more marital problems, have more mental health issues and display more family disfunctions in comparison to parents of healthy children. Especially
mothers of children with ASD show more psychopathology and marital problems (Shur-Fen Gau, Chou, Chiang, Lee, Wong and colleagues, 2012).
Being funny. Schizotypy and autism measures are to some extend linked with
appreciation of humor (Rawlings, 2008). High scores on AQ are associated with low scores on positive humor styles (Eriksson, 2013) and individuals with autism spectrum disorder score significantly lower on cheerfulness and higher on seriousness (Samson, Huber and Ruch, 2013). Schizophrenic patients also show deficits on humor appreciation (Polimeni, Campbell, Gill, Sawatzky and Reiss, 2010).
Looking different (physical appearance). To some extend changes in the appearance are
significantly associated with mild psychotic and pre-psychotic symptoms in a non-clinical sample (a` Campo, Nijman and Merckelbach, 2004). Vulnerability to develop psychotic
symptoms is especially linked to peculiar ways of dressing and frequent or remarkable changes of hair-dos (a` Campo et al., 2004).
Currently there are no self-administered instruments available to measure to what degreet an individual feels different from other people. There are scientific as well as applied reasons for such an instrument. If people with autistic and schizotypy traits feel different from other people this could shed more light on the nature of the relation between autistic and schizotypy traits. It could imply that there is possibly a broader phenotype of certain traits which, indirectly, could have implications for the used approach to both disorder spectra.
3. Materials and methods
Current research was approved by the Ethical Committee at University of Amsterdam.
3.1. Participants
Data was collected from 104 participants (37 males and 67 females). The mean age of the participants was 28.9 (SD=1, 15). All participants signed an informed consent before they could proceed with filling in the questionnaire.
3.2. Feeling Different Questionnaire (FD)
This is a newly developed questionnaire to assess basic personal information and the extent to which someone considers him/herself to be different from other people. It was designed to be easy to use and to score. It comprises the following 13 facets:
● Looking different (physical appearance) ● Being creative
● Being funny ● Being showy ● Being obstructive ● Having mood swings ● Having different opinions
● Feeling lonely and not understood ● Liking to be on your own
● Not understanding the world around you ● Having different skills
● Having different interests and hobbies ● Coming from a strange family / background
We aimed to develop ten questions related to these 13 different facets. The first final version consisted of informed consent, information about the research and 152 questions (9 scales with 10 questions, 2 scales with 11 questions, 2 scales with 12 questions and 16 questions about basic personal information). All questions (except 16 questions about basic personal information) are scored based on a four-point Likert scale: strongly agree, slightly agree, slightly disagree and strongly disagree, scaled from 4 to 1, respectively. The first version of Feeling Different questionnaire can be found in Appendix 1.
3.3. Procedure
The Feeling Different Questionnaire was available via the online survey site Qualtrics. The link for the FD was posted on Facebook. 104 participants completed the first final version of the questionnaire. Questions were presented in the random order to prevent order effect.
The questionnaire was available for the second time after two weeks, for those participants who agreed to fill it in once again (N=24).
4. Results
The proposed factor structure was not fully supported by the principal component analysis. Principal component analysis with varimax rotation was performed and items loadings onto each factor were reviewed for the common domain. As the result, we identified 13 factors, slightly different from the original 13 factors. The following components are forming the final version of
the Feeling Different Questionnaire:
dejection, consisting of 14 statements; creativity, consisting of 12 statements; willfulness, consisting of 9 statements; extraversion, consisting of 9 statements;
family (positive/negative), consisting of 6 statements; having outspoken opinion, consisting of 5 statements; stubborn, consisting of 7 statements;
expertise, consisting of 5 statements connectedness, consisting of 5 statements; different family, consisting of 5 statements;
sense of humor/being funny, consisting of 5 statements; active/outgoing, consisting of 5 statements;
appearance/clothing consisting of 5 statements;
The internal consistency of all 13 components was satisfactory. The Cronbach’s α was calculated for each of the 13 components and is presented in Table 1. Table 2 shows the eigenvalues of the 13 components.
For the validation purpose split-half and test-retest reliability analyzes were conducted. The Cronbach’s αs for spilt-half indicate good reliability (Cronbach’s α 1 = 0.858, Cronbach’s α 2 = 0.860). The overall Cronbach’s α for the FD questionnaire is 0.920.
Correlation between the test and retest scores was estimated using Spearman's rho and was 0.672.
The Feeling Different questionnaire in total consists of 106 questions. 92 statements are scored based on a four-point Likert scale: strongly agree, slightly agree, slightly disagree and strongly disagree, scaled from 4 to 1, respectively. 39 items are scored in the reversed manner (from 1 to 4). The remaining 14 questions are about basic personal information. The final version of the Feeling Different questionnaire can be found in Appendix 2.
Table 1. Cronbach’s α of 13 component of of Feeling Different questionnaire
Component Cronbach’s α Dejection 0,843 Creativity 0,922 Willfulness 0,890 Extraversion 0,853 Family (positive/negative) 0,823 Outspoken opinion 0,830 Stubborn 0,748 Expertise 0,748 Connectedness 0,616 Different family 0,787 Humor/being funny 0,818 Active/outgoing 0,710 Appearance/clothing 0,704
Table 2. Eigenvalues of 13 FD components
Component Initial Eigenvalues
Total % of Variance 1 2 3 4 5 6 7 8 9 10 11 12 13 15,654 14,861 7,682 6,548 4,326 3,824 3,525 3,374 3,068 3,016 2,918 2,716 2,607 11,510 10,927 5,649 4,815 3,181 2,811 2,59 2,481 2,256 2,218 2,146 1,997 1,917 19 | P a g e
5. Discussion
We have described a new instrument, the Feeling Different questionnaire, for measuring the degree to which an individual feels different from other people. The aim of this study was to evaluate whether the Feeling Different questionnaire is a valid instrument for measuring newly introduced variable feeling different from other people. The construct validity of the FD questionnaire is satisfactory, as items purporting to measure each of the 13 domains have high alpha coefficients. Also factor loadings of the items are satisfactory. The test-retest reliability of FD is moderate. These findings obviously need further evaluation. In particular, the subscale Connectedness should be revised carefully, as it had the lowest Cronbach's α. Possibly, better formulation of the questions/statements could improve this subscale. In case of no improvement of the internal consistency of Connectedness subscale, removal of this subscale should be considered.
To summarize, further refinement of the Feeling Different questionnaire is needed as well as validation on appropriate sample, preferably greater than the one in current study.
Part II “Overlap between autistic traits and schizotypy traits”
6. Materials and methods
6.1. Participants
Initially, a total number of 193 participants was recruited for this study. Participants were
approached via www.lab.uva.nl (digital research credit system) and Facebook, were the link to the online questionnaire was available. Some participants were also approached via e-mail, using social network of the researcher. A total of 154 subjects completed the questionnaire. A total of 15 participants with other then European and North-African background were excluded.
6.2 Materials
All questionnaires were administered through an online survey on Qualtrics.com as one set of questions and statements. The questionnaires began with an introductory part followed by AQ – short questionnaire, BRIEF-A questionnaire, O-LIFE – short questionnaire, QBF questionnaire, FD questionnaire and a closing statement.
6.2.1. Autism Spectrum Quotient (AQ)
The Autism Spectrum Quotient (AQ) measures autistic traits on a continuum. In the general population these autistic traits are normally distributed (Baron-Cohen et al., 2001). The AQ consists of five factors (Hurst et al., 2007), which are represented by following domains: social
skill scale, attention switching scale, imagination scale, attention to detail scale and communication scale. AQ contains 50 items which are scored based on a four-point Likert scale: strongly agree, slightly agree, slightly disagree and strongly disagree, scaled from 1 to 4, respectively. 26 items are scored in the reversed manner (from 4 to 1). The AQ has good psychometric properties (Austin, 2005). Test-retest reliability and internal consistency for the Dutch version of the AQ are satisfactory (Hoekstra, Bartels, Cath and Boomsma, 2008).
AQ - short is a 28-item alternative to full 50-items questionnaire. The validity of this short version was established on 3 independent samples, both clinical and controls (Hoekstra et al, 2011). AQ – short consists of five subscales: social skills, routine, switching, imagination and patterns.
6.2.2. Oxford-Liverpool Inventory of Feelings and Experience short
Oxford-Liverpool Inventory of Feelings and Experience (O-LIFE) aims to measure all aspects of schizotypy and it is a 104 item questionnaire divided in 4 scales: unusual experiences, cognitive disorganization, introvertive anhedonia and impulsive nonconformity. The items can be answered by a “yes” or “no” response. The O-LIFE has good predictive validity for schizotypy traits (Linney, Murray, Peters, MacDonald and Rijsdijk, 2003). The internal consistency for the Dutch version of the O-LIFE is satisfactory (Veldkamp, 2010).
The short version of O-LIFE questionnaire consists of 43 items and is divided in the same 4 scales as the long version of O-LIFE questionnaire. The validity of all 4 scales exceeded 0.9. The internal consistency of the 4 scales varies from 0.62 to 0.80.
6.2.3. Quick Big Five (QBF)
Quick Big Five (QBF) measures personality traits according to the Big Five model. The QBF consists out of 30 items and is divided in the following dimensions:
− extraversion which consists of following adjectives: restraint, quiet, closed, talkative, timid, withdrawn;
− agreeableness which consists of following adjectives: pleasant, helpful, friendly, kind, enjoyable, sympathetic;
− conscientiousness which consists of following adjectives: sloppy, careful, orderly, precise, neat, systematic;
− neuroticism which consists of following adjectives: irritable, nervous, emotional, worry, anxious, nervous and;
− openness which consists of following adjectives: imaginative, inquisitive, versatile, innovative, artistic, creative.
The internal consistence of each QBF dimensions is as follows: for extraversion Cronbach’s alpha = .88, for conscientiousness Cronbach’s alpha = .86, for agreeableness Cronbach’s alpha = .83, for neuroticism Cronbach’s alpha = .82, and for openness Cronbach’s alpha = .74. All internal consistencies are thus adequate or high. The test-retest reliability of the scale was found to be acceptable (Vermulst and Gerris 2005).
6.2.4. Behavioral Rating Inventory of Executive Function Adults (BRIEF - A)
Behavioral Rating Inventory of Executive Function Adults (BRIEF - A) aims to assess executive functioning on the behavioral level. BRIEF consists of nine clinical scales (Inhibit, Shift, Emotional Control, Self-Monitor, Initiate, Working Memory, Plan/Organize, Task-Monitor,
Organization of Materials) and two validity scales (Inconsistency and Negativity).
The clinical scales form two broader indices (Behavioral Regulation and Metacognition) and an overall score, the Global Executive Composite.
The test-retest reliability for BRIEF-A is satisfactory. Correlation coefficient for Behavioral Regulation scale is 0.73, correlation coefficient for Metacognition scale is 0,78 and the correlation coefficient for self-rapport total is 0,77 (Everts et al., 2000) and standardized scores are available for age, sex and nationality.
The internal consistency of BRIEF-A is also satisfactory with Cronbach alfa for self-rapport total = 0.96, Cronbach alfa for Behavioral Regulation scale =: 0.92 and Cronbach alfa for Metacognition scale = 0.94.
The items of the BRIEF-A subscales are representative for executive functions.
6.2.5. Feeling Different questionnaire
This is a newly developed questionnaire to assess basic personal information and the extent to which someone considers him/herself to be different from other people.
The following components are forming the final version of the Feeling Different questionnaire: dejection, consisting of 14 statements;
creativity, consisting of 12 statements; willfulness, consisting of 9 statements; extraversion, consisting of 9 statements;
family (positive/negative), consisting of 6 statements; having outspoken opinion, consisting of 5 statements;
stubborn, consisting of 7 statements; expertise, consisting of 5 statements connectedness, consisting of 5 statements; different family, consisting of 5 statements;
sense of humor/being funny, consisting of 5 statements; active/outgoing, consisting of 5 statements;
appearance/clothing consisting of 5 statements.
Feeling Different questionnaire consists 106 questions. 92 statements are scored based on a four-point Likert scale: strongly agree, slightly agree, slightly disagree and strongly disagree, scaled from 4 to 1, respectively. 39 items are scored in the reversed manner (from 1 to 4).The remaining 14 questions are about basic personal information. The final version of the Feeling Different questionnaire is show in Appendix 2. The factor loadings of 13 components are presented in Appendix 3.
6.3. Procedure
The data was collected online via the Qualtrics survey tool. Participants filled in the questionnaires either at the University of Amsterdam or at places with internet access.
The questionnaires were presented in following order: Autism Spectrum Quotient short (AQ - short), Behavioral Rating Inventory of Executive Function Adults (BRIEF - A), Oxford-Liverpool Inventory of Feelings and Experience short (O-LIFE short), Quick Big Five and new questionnaire “Feeling Different” (FD).
6.4. Statistical analysis
Based on previous research, we assumed that the traits we measured were normally distributed in the general population. Therefore we used the Pearson product-moment correlation coefficient. All hypotheses are confirmed when the correlation coefficient is significantly different from 0. To further explore the relation between the different variables, a regression analysis was performed, to examine the unique variance that the variables executive function, neuroticism, extraversion and feeling different from other persons explained in autistic and schizotypy traits. A partial correlation coefficient was calculated between autistic traits and schizotypy traits after controlling for the variables executive function, neuroticism, extraversion and feeling different from other people.
7. Results
7.1 Descriptive statistics
Table 1 shows the descriptive statistics for the subscales of the five questionnaires employed, referring to the range of the scores, minimum and maximum, standard deviation and kurtosis.
Table 1. Descriptive statistics for the subscales of the five questionnaires.
Range Minimum Maximum Mean Std. Deviation Kurtosis
AQ Social Skills 19.00 7.00 26.00 11 .8 9 93 3.26886 1.751 Routine 10.00 4.00 14.00 7.9065 2.41641 -.656 Switching 11.00 4.00 15.00 8.8129 2.32681 .023 Imagination 18.00 8.00 26.00 14.6763 3.38200 -.008 Patterns 13.00 5.00 18.00 9.8273 3.17127 -.617 O-LIFE Unusual Experience 01-11-00 .00 11.00 3.3022 2.47496 .479 26 | P a g e
Cognitive Disorganization 11.00 .00 11.00 4.1799 2.92479 -.667 Introvertive Anhedonia 8.00 .00 8.00 1.1655 1.63120 3.158 Impulsive Nonconformity 9.00 .00 9.00 2.8417 2.10678 -.309 BRIEF-A Inhibit 14.00 8.00 22.00 13.9856 2.78710 .176 Shift 12.00 6.00 18.00 9.6547 2.20905 .677 Emotional Control 16.00 10.00 26.00 15.8993 4.37598 -.972 Self- Monitor 9.00 6.00 15.00 9.0144 2.07813 -.263 Initiate 14.00 8.00 22.00 14.1583 3.21513 -.500 Working Memory 16.00 8.00 24.00 13.4388 3.21481 .283 Plan Organize 18.00 10.00 28.00 17.0288 3.83149 -.156 Task Monitor 11.00 7.00 18.00 11.2374 2.17223 .489 Organization Materials 16.00 8.00 24.00 15.2878 4.10945 -.699 QBF Agreeableness 20.00 22.00 42.00 35.1367 3.35616 1.393 Extraversion 31.00 11.00 42.00 28.2230 7.20612 -.610 Conscientiousness 34.00 8.00 42.00 25.6763 7.68324 -.547 Neuroticism 33.00 9.00 42.00 26.9568 6.40750 -.053 Openness 28.00 13.00 41.00 28.7482 5.62228 -.186 FD Dejection 34.00 15.00 49.00 27.4820 7.90373 -.282 Creativity 34.00 12.00 46.00 27.7698 8.48555 -.910 Willfulness 20.00 12.00 32.00 20.3094 4.99543 -.922 Extraversion 17.00 15.00 32.00 24.3957 3.93722 -.578
Family Positive Negative 18.00 6.00 24.00 11.4820 3.60023 .714
Outspoken opinion 8.00 8.00 16.00 12.1079 1.59569 .144
Stubborn 15.00 13.00 28.00 19.7554 3.15044 -.294
Expertise 10.00 7.00 17.00 12.4029 2.26735 -.704
Connectedness 11.00 6.00 17.00 9.9065 2.15316 -.143
Family Different 15.00 5.00 20.00 11.6978 3.85734 -.646
Having sense of humor 14.00 5.00 19.00 10.3309 2.86252 .402
Active/outgoing 12.00 5.00 17.00 10.2302 2.54899 -.412
Appearance 14.00 5.00 19.00 10.6187 2.80113 -.060
7.2. Autistic traits and schizotypy traits
There was a significant correlation between AQ – short scores and O-LIFE – short scores (r = 0.465, p < 0.001). Table 2 shows the Pearson correlations between the AQ – short subscales and O-LIFE – short subscales. The results showed that Cognitive Disorganization and Introvertive Anhedonia subscales correlated significantly with all the subscales of the AQ – short. The
Unusual Experience subscale of the O-LIFE – short correlated significantly with all the subscales of the AQ – short, except for Switching subscale of the AQ – short. The Impulsive
Nonconformity subscale of the O-LIFE – short correlated significantly with two AQ – short subscales: Switching and Patterns.
To account more accurately for the shared variance of the AQ – short and O-LIFE – short a partial correlation analysis was conducted controlling for the following variables: feeling different (FD total score), executive functions (BRIEF-A total score), neuroticism and extraversion scores.
After controlling for FD scores on AQ – short and O-LIFE – short the correlation was smaller but still significant (r = 0,363, p < 0,001). Also after controlling for BRIEF-A score (r = 0.281, p < 0.001), neuroticism (r = 0.335, p < 0.001) and extraversion (r = 0.321, p < 0.001) the
correlations were smaller but still significant.
Table 2. Pearson correlations between O-LIFE short and AQ-shirt subscales OLIFE
AQ
Unusual Experience Cognitive Disorganization Introvertive Anhedonia Impulsive Nonconformity
Social Skills .160* .332** .658** .079
Routine .151* .332** .521** .117
Switching .090 .446** .222** .195*
Imagination -.159* .233** .336** .013
Patterns .224** .289** .195* .201**
7.2.1. Autistic traits and feeling different
There was a significant correlation between scores on AQ – short and FD questionnaire (r = 0.328, p < 0.001). Tables 3a and 3b show the Pearson correlations between AQ-short subscales and FD subscales. Dejection and Connectedness subscales of FD correlated significantly with all AQ – short subscales, with the highest correlation with Social Skills subscale. Notably Creativity subscale of FD correlated negatively and significantly with two AQ – short subscales: Routine and Imagination. Extraversion subscale of FD correlated significantly with all AQ – short subscales except for Patterns subscale. Family (positive/negative) subscale of FD correlated significantly only with Social Skills subscale of AQ – short. Also Outspoken Opinion subscale od FD correlated significantly with one AQ – short subscale (Patterns). There were no significant correlations between Stubborn subscale of FD and any AQ – short subscales. Expertise subscale
of FD correlated negatively and significantly with three AQ – short subscales: Social Skills, Routine and Imagination. Family Different subscale of FD correlated negatively and
significantly with Imagination subscale of AQ – short. Active/Outgoing subscale of FD
correlated significantly with all AQ – short subscales, except for Patterns subscale. Appearance subscale of FD correlated negatively and significantly with Imagination subscale of AQ – short and positively and significantly with Patterns subscale.
To further explore the relation between AQ – short score and FD score linear regression was conducted. When FD score was entered as predictor it was found to account for 10,8% of the variance (F = 16,543, p< 0.001).
Table 3a. Pearson correlations between AQ and FD.
AQ FD
Dejection Creativity Willfulness Extraversion Family_P_N Outspoken opinion
Social Skills .499** -.134 .292** .532** .177* .080 Routine .389** -.171* .164* .346** .051 .012 Switching .354** -.008 .115 .275** .054 .023 Imagination .317** -.372** .106 .269** .090 .020 Patterns .183* .001 .161* .047 .029 .180*
Table 3b. Continuation of Pearson correlations between AQ subscales and FD subscales. AQ
FD
Stubborn Expertise Connectedness Family Different Humor Active/Outgoing Appearance Social Skills .004 -.153* .543** .040 .217** .552** .074 Routine -.024 -.176* .443** -.090 .240** .301** .064 Switching -.009 -.020 .212** .062 -.096 .184* .066 Imagination -.090 -.203** .270** -.165* .126 .190* -.214** Patterns .048 -.076 .172* -.005 -.121 .102 .153* 30 | P a g e
7.2.2. Autistic traits and executive functions
There was significant correlation between the total AQ – short score and BRIEF-A score (r = 0.403, p<0.001). Table 4 shows the Pearson correlations between AQ – short subscales and BRIEF-A subscales. The highest correlations were apparent between Shift subscale of BRIEF-A and two subscales of AQ – short: Social Skills and Routine. Also Working Memory subscale of BRIEF-A correlated highly and significantly with AQ – short subscale Switching. Initiate subscale of BRIEF-A correlated moderately with AQ – short subscale Switching.
To explore more closely the relationship between autistic traits and executive functions the linear regression was conducted. When BRIEF-A score was entered as predictor it accounted for 16.3% of the variance (F = 26.620, p, < 0 .001).
Table 4. Pearson correlations between AQ – short and BRIEF-A
AQ BRIEF-A
Emotional Control
Inhibit Shift Self- Monitor Initiate Working
Memory Plan Organize Task Monitor Organization of Materials Social Skills .373** -.128 .555** .038 .268** .198** .147* .065 .030 Routine .199** -.025 .614** .061 .235** .177* .124 -.005 .005 Switching .126 .205** .381** .131 .424** .538** .402** .268** .219** Imagination .096 -.012 .395** .180* .239** .254** .255** .042 .141* Patterns .079 .224** .118 .253** .202** .132 .182* .070 .066
7.2.3. Autistic traits and personality traits
There was significant negative correlation between AQ – short score and extraversion score (r = -0.575, p< 0.001). Correlation between AQ – short score and neuroticism was also negative and significant (r = -0.422, p< 0.001).
To further examine the relation between autistic traits extraversion and neuroticism a linear 31 | P a g e
regression was conducted. When extraversion was entered as a predictor it was found to account for 33.1% of the variance (F = 67.759, p <0.001). When neuroticism was entered as a predictor it was found to account for 17.8% of the variance (F = 29.623, p < 0.001)
7.3.1. Schizotypy traits and feeling different
There was significant correlation between O-LIFE – short and FD (r = 0.537, p < 0.001). Tables 6a and 6b show the Pearson correlations between subscales of O-LIFE – short and FD. Dejection subscale of FD correlated significantly with all O-LIFE – short subscales. Notably the highest correlation was apparent between Dejection subscale of FD and Cognitive Disorganization subscale of O-LIFE – short. Willfulness, Connectedness and Family (positive/negative) subscales of FD also correlated significantly with all subscales of O-LIFE – short. Outspoken opinion correlated significantly with all O-LIFE – short subscales except for Cognitive Disorganization. FD subscale Expertise correlated significantly with all O-LIFE – short subscales except for Unusual Experiences subscale. FD subscale Family Different did not correlate significantly with any of the O-LIFE – short subscales. FD subscales Humor and Active/Outgoing both correlated significantly with Cognitive Disorganization and Introvertive Anhedonia scales of O-LIFE – short.
To further explore the relationship between schizotypy traits and feeling different a linear regression was conducted. When FD was entered as a predictor it was found to account for 28.8% of the variance (F = 55.503, p < 0.001).
Table 6a. Pearson correlations between O-LIFE – short and FD.
OLIFE
FD
Dejection Creativity Willfulness Extraversion Family_P_N Outspoken opinion
Unusual Experience .345** .077 .346** .132 .251** .151* Cognitive Disorganization .687** .024 .204** .322** .243** .117 Introvertive Anhedonia .387** -.181* .287** .308** .210** .171* Impulsive Nonconformity .492** -.035 .272** .089 .194* .354**
Table 6b. Continuation of Pearson correlations between O-LIFE subscales and FD subscales.
O-LIFE
FD
Stubborn Expertise Connectedness Family
Different Humor Active/ outgoing Appearance Unusual Experience .149* -.086 .241** .138 .032 .115 .203** Cognitive Disorganization -.009 -.337** .367** .042 .148* .144* .038 Introvertive Anhedonia .056 -.245** .539** .000 .148* .426** .003 Impulsive Nonconformity .366** -.194* .305** .179* -.036 .023 .171*
7.3.2. Schizotypy traits and executive functions
There was a significant correlation between O-LIFE – short and BRIEF-A (r = 0.695, p < 0.001). Table 7 shows the Pearson correlations between O-LIFE – short subscales and BRIEF-A
subscales. Shift, Emotional Control, Self- Monitor, Initiate, Working Memory, Plan Organize and Task Monitor subscales of BRIEF-A correlated significantly with all O-LIFE – short subscales. Inhibit and Organization Materials subscales of BRIEF-A correlated significantly with all O-LIFE – short subscales except for Introvertive Anhedonia.
To further examine the relationship between schizotypy traits and executive functions a linear 33 | P a g e
regression was conducted. When BRIEF-A was entered as a predictor it was found to account for 48.3% of the variance (F = 128.052, p < 0.001).
Table 7. Pearson correlations between O-LIFE – short and BRIEF-A. O-LIFE
BRIEF-A
Inhibit Shift Emotional
Control Self- Monitor Initiate Working Memory Plan Organize Task Monitor Organization Materials Unusual Experience .344** .211** .272** .333** .214** .240** .237** .212** .166* Cognitive Disorganization .504** .519** .449** .369** .580** .646** .575** .411** .350** Introvertive Anhedonia .071 .468** .168* .162* .371** .256** .242** .183* .118 Impulsive Nonconformity .608** .220** .310** .408** .375** .351** .341** .330** .245**
7.3.3. Schizotypy traits and personality traits
There was negative significant correlation between O-LIFE – short and extraversion (r = -0.388, p < 0.001). Also neuroticism and OLIFE – short correlated negatively and significantly (r = -0.466, p < 0.001).
For both variables (extraversion and neuroticism) a linear regression was conducted. When extraversion was entered as a predictor it accounted for 15.1% of the variance (F = 24.306, p < 0.001). When neuroticism was entered as a predictor it accounted for 21.7 % of the variance (F = 37.963, p < 0.001)
7.3.4 Executive functions, personality and feeling different
There was significant correlation between BRIEF-A and FD (r = 0.395, p < 0.001). Tables 8a and
8b show the Pearson correlations between BRIEF-A subscales and FD subscales.
Dejection subscale of FD correlated significantly with all BRIEF-A subscales. Notably the highest correlations were apparent with Emotional Control , Shift, Initiate and Plan Organize, respectively. Expertise subscale of FD correlated significantly with all BRIEF-A subscales except for Emotional Control. There was no significant correlation between Family Different subscale of FD with any BRIEF-A subscales. Furthermore, a negative significant correlation was found between Humor subscale and Inhibit subscale of BRIEF-A. Appearance subscale of FD did not correlate significantly with any of the BRIEF-A subscales.
There was negative significant correlation between BRIEF-A and extraversion (r = - 0.309, p < 0.001) as well as between BRIEF-A and neuroticism (r = - 0.445, p < 0.001). FD also correlated negatively and significantly with both extraversion (r = - 0.385, p < 0.001) and neuroticism (r = - 0.459, p< 0.001).
Table 8a. Pearson correlations between BRIEF-A and FD.
BRIEF
FD
Dejection Creativity Willfulness Extraversion Family P N Outspoken opinion
Inhibit 281** .078 .131 -.077 .129 256** Shift 538** -.169* .195* 347** .132 .054 Emotional Control 578** .093 292** .180* 259** 230** Self-Monitor 310** -.085 .098 .010 .146* .142* Initiate .526** -.014 .060 .243** .239** .066 Working Memory .476** .059 .154* .168* .256** .126 Plan Organize .453** .009 .087 .173* .235** .049 Task Monitor .255** .080 -.038 .176* .022 .135 Organization of Materials .320** .065 .058 .014 .057 .087 35 | P a g e
Table 8b. Continuation of Pearson correlations between BRIEF-A subscales and FD subscales.
BRIEF
FD
Stubborn Expertise Connectedness Family Different Humor Active/Outgoing Appearance
Inhibit 307** -.270** .145* .092 -.141* -.134 .072 Shift .089 -.196* 464** .019 277** 311** .090 Emotional Control 293** -.079 284** .037 282** 290** .094 Self-Monitor 233** -.343** 217** .011 .097 .043 -.015 Initiate -.035 -.213** .285** .107 -.055 .062 -.083 Working Memory .009 -.333** .224** .083 .012 .008 -.046 Plan Organize -.044 -.314** .259** .096 -.005 .042 -.046 Task Monitor .039 -.248** .149* -.003 .039 .011 -.060 Organization of Materials -.031 -.239** .129 .049 -.008 -.052 .001
8. Discussion and conclusion
The main goal of the present study was to investigate the relationship between autistic traits and schizotypy traits and their association with executive functions, personality and anew variable “feeling different from other people” in the general Dutch population.
As hypothesized autistic and schizotypy traits were positively and significantly correlated. This confirms earlier findings (Russell-Smith et al., 2011; Hurst et al., 2007; Dinsdale et al., 2013) that there is an overlap between autistic and schizotypy traits in the general population.
Our exploratory hypothesis that autistic traits will positively correlate with the newly introduced variable “feeling different” was confirmed. Likewise, the hypothesis that schizotypy traits will positively correlate with feeling different was confirmed. Although the correlation between autistic traits and feeling different was not as high as between schizotypy traits and feeling different, both were significant, indicating that there is an association between those traits and feeling different from other people. In particular, high correlation was found between Dejection
subscale of FD and Cognitive Disorganization scale of O-LIFE – short. This result is in line with findings in clinical patients, where depressive moods appear to influence cognitive deficits (Iosifescua et al., 2012).
Also, high correlation was found between Connectedness subscale of FD and Introvertive Anhedonia of O-LIFE – short. This result suggests that schizotypy traits are connected to self-stigma in the general population, as it is seen in schizophrenic patients (Dopke and Batscha, 2014)
Furthermore, the results from linear regression indicate that both autistic and schizotypy traits could be predicted by FD score. Therefore FD could be useful as an additional tool in assessment of impairments linked to autism spectrum disorders and schizophrenia spectrum disorders. The results are promising, however caution is needed for their interpretation. The Feeling Different questionnaire is a novel instrument and was tested only twice. Nevertheless, our findings could be of value for better understanding of the relationship between autistic traits and schizotypy traits, as well as, in broader picture, for better understanding of autism and
schizophrenia disorder spectra.
With regard to executive function we found that scores on BRIEF-A correlated significantly with autistic traits. Although BRIEF-A does not measure the whole spectrum of executive functions, it is a good instrument to assess executive functions on behavioral level. Bearing this in mind, our findings indicate that executive disfunctioning, to some extent, is linked to autistic traits. These findings, however novel, are in agreement with previous results in autistic patients (Rogers et al., 2006; Hill, 2004).
Additionally, as hypothesized, schizotypy traits and executive functions correlated significantly. 37 | P a g e
Again, this finding suggests that there is an association between schizotypy traits and executive functions on behavioral level, which is in line with previous research findings in schizophrenia spectrum disorders. (Pickup, 2008; Kravariti etal., 2005).
Interestingly, the correlation was again higher for schizotypy traits than for autistic traits, as is case with feeling different scores. It is possible that high levels of cognitive disorganization, which is characteristic of schizotypy traits but not of autistic traits, results in higher level of executive disfunction.
Moreover, autistic traits and schizotypy traits could be predicted from the score on BRIEF-A. These novel findings imply that there is a link between autistic traits, schizotypy traits and executive functions also in the general population. As cognitive impairments are present in both autism spectrum disorders and in schizophrenia spectrum disorders better understanding of the association between cognitive functioning in general and characteristics of those disorder spectra could be of value for assessing the range and severity of the impairments.
Furthermore, our hypothesis that autistic traits will negatively correlate with extraversion were confirmed. This finding is compatible with results from autistic patients where low extraversion levels are found (Wakabayashi et al., 2006).
Although significant correlations were found between autistic traits and neuroticism as well as between schizotypy traits and neuroticism, both correlations were negative. Therefore our hypotheses that there will be positive correlation between autistic traits, schizotypy traits and neuroticism were not confirmed. These results are also not in agreement with previous findings (Wakabayashi, et al., 2006; Herran et al., 2006). Possiblythis pattern of personality is seen only in people with diagnosed disorder (autism spectrum disorder or schizophrenia spectrum disorder)
and is not associated with autistic and schizotypy traits in general population. Establishing better profile of personality could be advantageous in forming broader phenotype for autism spectrum disorders and schizophrenia spectrum disorders. This, in turn, could provide improvements in behaviorally applied therapies in both disorder spectra.
The results from partial correlations revealed that even after controlling for feeling different, executive functions, neuroticism and extraversion, correlation between autistic traits and schizotypy traits was still significant. This finding combined with previous results (Russell-Smith et al., 2011; Hurst et al., 2007; Dinsdale et al., 2013) support the evidence of overlap between autistic and schizotypy traits.
To summarize, our research, combined with recent findings of Russell-Smith and colleagues (2013) enhances better understanding of the association between autistic traits and schizotypy traits. Better assessments of impairments and disfunctions connected to autism spectrum disorder and schizophrenia spectrum disorder is of value for the scientific as well as applied reasons. When more is known about the autistic traits and schizotypy traits, better estimation can be made of their impact on the general functioning of an individual exhibiting those traits. Indirectly, this could lead to better estimation of impairment and disfunctions in autism spectrum disorders and schizophrenia spectrum disorders. Consequently, as the greater insight in the functioning is gained, broader and improved approach in cognitive and behavioral treatment for autism spectrum disorder and schizophrenia spectrum disorder could be applied.
8.1 Limitations
At this point our findings show promise, but definite conclusions cannot be drawn yet. Further
investigation of the feeling different concept is needed to establish the extend and number of factors associated with both autistic and schizotypy traits. Careful revision of the items in the Feeling Different questionnaire is required to eliminate possible overlap with items which measure autistic and schizotypy traits. Also meticulous revisal of the proposed facets of the Feeling Different questionnaire is advised. Especially the subscale Connectedness requires additional investigation because of its low internal consistency. Therefore re-evaluation, further validation and refinement of the Feeling Different questionnaire is of great importance.
Additionally, better assessment of executive functions is advised. For the purpose of this research a self-report questionnaire was used. However, more objective measurements of this domain could be obtained if acquired by professional clinicians.
Lastly, a greater and more differentiated sample size is desirable to obtain more accurate and generalizable conclusions.
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