Characterizing Repetitive Behaviors & Interests Specific to Autism: The Autistic Interests Scale

Characterizing Repetitive Behaviors & Interests Specific to Autism: The Autistic Interests Scale

Introduction

Autism is a phenotype which is well known to be characterized in part by repetitive, stereotyped, restricted behavior and interests (e.g., Baron-Cohen et al. 2001; Mirenda et al. 2010). While repetitive behavior is an aspect of the autism phenotype, repetitive behavior in general is largely not specific to autism, and aspects such as intense investment in interests and fidgeting are often present in schizotypy (Jones et al. 2015), borderline personality (Dell’Osso et al. 2018), and OCD (Cloudfindings 2021a). This can make the identification of repetitive behavior caused by an autism spectrum disorder as opposed to a different disorder difficult, and may confound the measurement of autistic traits with repetitive behavior caused by other phenotypes, as has been the case with measuring social deficits in autism (Cloudfindings 2021b, 2022a)(Crespi 2021)(Del Giudice et al. 2014). To remedy this, I created an 8-item scale [Table 1] with items intending to reflect repetitive behaviors and interests with characteristics specific to autism


Table 1

Item	Justification
My strongest interests are in movies, shows, books, or video games	While not recognized much in scientific literature, the online autistic community has recognized strong interests directed particularly toward media as being very common in autism. This is consistent with the finding that autism involves a strong drive to collect facts about topics (Baron-Cohen et al. 2003)
My strongest interests are in mechanical things (e.g., trains,  computers, fire alarms, etc)	Autism often involves interests in technical subjects and increased mechanistic cognition (Baron-Cohen et al. 2001, 2003)(Badcock & Crespi 2006). This may also differentiate from schizotypy, as schizotypy is associated with creative, artistic, or socially oriented interests rather than mechanical or technical ones (Cloudfindings 2022b)
I like to learn as many facts as I can about my interests	Autism involves a strong drive to collect facts about topics of interest (Baron-Cohen et al. 2003). In contrast, schizotypy may involve a creative and exploratory approach to topics of interest (Cloudfindings 2022b)
When I find something I like, or enjoy, I tend to do it over and over or “obsess” over it	Autism involves intense, stereotyped interests (Mirenda et al. 2010)
It is important that people I am friends with like the same things as me	Social interaction in autistic people tends to be motivated by fulfillment of personal interests rather than the act of socializing in itself (Baron-Cohen 2005)
It is important that people I am friends with share the same beliefs as me	Autistic people tend to hold strong beliefs and have difficulty compromising with others perspectives (Baron-Cohen 2005)
I prefer to do the same things every day in the same order	Autistic people tend to prefer consistent day-to-day routines and experience distress when they are not able to follow through with them (Crespi 2021). This may differentiate from other forms of repetitive behaviors and rituals that characterize schizotypy, such as counting compulsions (Sobin et al. 2000)
I like internet memes	Internet memes typically surround references to specific topics or pop culture as opposed to other types of jokes which require mentalizing to interpret (Cloudfindings 2021b)

Study & Results

Among other measures (which will be reported on in separate posts as they address different topics), I included the eight items of this scale, as well as the imagination subscale of the autism-spectrum quotient (AQ, Baron-Cohen et al. 2001), the literal language scale (Cloudfindings 2021b), and the unusual experiences subscale of the short O-LIFE to measure positive schizotypy (Mason et al. 2005). Participants were also asked to report whether they were diagnosed with or suspected an autism spectrum disorder and a schizophrenia spectrum disorder. The survey data was collected using PsyToolkit (Stoet 2010, 2017) and had a total of 122 participants who had fully completed the survey. 

 

Principal components analysis was used to test if the items of the scale reflected a common latent factor. All items loaded on the first principal component in the same direction, however the loading for “I like internet memes” was relatively small (r=0.29) [Table 2].

Table 2

Item	PC1 Loading
My strongest interests are in movies, shows, books, or video games	0.31
My strongest interests are in mechanical things (e.g., trains,  computers, fire alarms, etc)	0.37
I like internet memes	0.29
I like to learn as many facts as I can about my interests	0.64
When I find something I like, or enjoy, I tend to do it over and over or “obsess” over it	0.50
It is important that people I am friends with like the same things as me	0.74
It is important that people I am friends with share the same beliefs as me	0.60
I prefer to do the same things every day in the same order	0.63

 

The items of the literal language scale and unusual experiences scale were put through a principal components analysis to identify and obtain scores for the latent bipolar schizotypy-autism factor identified in previous studies (Cloudfindings 2022a)(Del Giudice 2014). This factor emerged as in previous studies as the second principal component [Table 3].

Table 3

Item	PC1	PC2
When in the dark do you often see shapes and forms even though there is nothing there?	-0.453	0.39
Are your thoughts sometimes so strong that you can almost hear them?	-0.532	0.27
Have you ever thought that you had special, almost magical powers?	-0.484	0.40
Have you sometimes sensed an evil presence around you, even though you could not see it?	-0.402	0.48
Do you think that you could learn to read other’s minds if you wanted to?	-0.377	0.43
When you look in the mirror does your face sometimes seem quite different from usual?	-0.388	0.46
Do ideas and insights sometimes come to you so fast that you cannot express them all?	-0.512	0.33
Can some people make you aware of them just by thinking about you?	-0.238	0.41
Does a passing thought ever seem so real it frightens you?	-0.459	0.44
Do you feel that your accidents are caused by mysterious forces?	-0.337	0.47
Do you ever have a sense of vague danger or sudden dread for reasons that you do not understand?	-0.521	0.32
Does your sense of smell sometimes become unusually strong?	-0.266	0.30
People tell me I "take things too seriously"	-0.309	-0.38
I often miss the point of jokes	-0.675	-0.40
I often don't pick up when someone is being sarcastic	-0.663	-0.42
Most words or phrases have only one meaning	-0.491	-0.55
I have trouble "reading between the lines" of what other people say	-0.631	-0.44
Unless otherwise specified, I assume that people mean exactly what they say.	-0.656	-0.39
I stick to the technical meaning of words rather than what other people think they mean.	-0.403	-0.65
The meaning of a word is determined by its dictionary definition	-0.366	-0.56

Correlations between the schizotypy-autism factor, PC1 scores for autistic interests, imagination AQ subscale (scored so higher scores reflect increased imagination and lower autistic traits), literal language, and suspected or diagnosed autism and schizophrenia-spectrum disorders were then tested [Table 4] (correlations with suspected or diagnosed disorders are spearman due to being reported on a four point scale, making the relationships non-linear). Autistic interests correlated in the direction of autistic traits with all measures, and predicted suspected or diagnosed autism (r=0.50). This supports the validity of the autistic interests scale to measure repetitive behaviors & interests that characterize autism. 

Table 4

	Autistic Interests	Schizotypy-Autism	Literal Language	Imagination
Schizotypy-Autism	-0.30
Literal Language	0.51	-0.67
Imagination	-0.19	0.40	-0.47
Suspect or Diagnosed ASD	0.51	-0.19	0.45	-0.39
Suspect or Diagnosed SSD	-0.08	0.30	0.02	0.05

1. Baron-Cohen et al. (2001) The Autism-Spectrum Quotient (AQ): Evidence from Asperger Syndrome/High-Functioning Autism, Males and Females, Scientists and Mathematicians
2. Mirenda et al. (2010) Validating the Repetitive Behavior Scale-Revised in Young Children with Autism Spectrum Disorder
3. Jones et al. (2015) The Melbourne Assessment of Schizotypy in Kids: A Useful Measure of Childhood Schizotypal Personality Disorder
4. Dell’Osso et al. (2018) Correlates of autistic traits among patients with borderline personality disorder
5. Cloudfindings (2021a) The Shared Etiology of Obsessive-Compulsive Behavior and Autistic Repetitive Behavior
6. Cloudfindings (2022a) Literal Language, Schizotypy, and Gender Dysphoria
7. Cloudfindings (2021b) Literal Language Scale: Development & Association With Social Intelligence
8. Crespi (2021) How is quantification of social deficits useful for studying autism and schizophrenia?
9. Del Giudice et al. (2014) Autistic-like and schizotypal traits in a life history perspective: diametrical associations with impulsivity, sensation seeking, and sociosexual behavior
10. Esterberg et al. (2015) Childhood and Current Autistic Features in Adolescents with Schizotypal Personality Disorder
11. Esterberg et al. (2013) Prodromal and Autistic Symptoms in Schizotypal Personality Disorder and 22q11.2 Deletion Syndrome
12. Baron-Cohen et al. (2003) The Systemising Quotient (SQ): An investigation of adults with Asperger Syndrome or High Functioning Autism and normal sex differences
13. Badcock & Crespi (2006) Imbalanced genomic imprinting in brain development: an evolutionary basis for the aetiology of autism
14. Cloudfindings (2022b) Autism and Schizotypy as Diametrical Disorders of Plasticity
15. Baron-Cohen (2005) Autism «Autos»: Literally
16. Crespi (2021) Pattern Unifies Autism
17. Sobin et al. (2000) Evidence of a schizotypy subtype in OCD
18. Stoet (2010). PsyToolkit - A software package for programming psychological experiments using Linux.
19. Stoet (2017). PsyToolkit: A novel web-based method for running online questionnaires and reaction-time experiments
20. Mason et al. (2005) Short scales for measuring schizotypy