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Structure of Restricted Repetitive Behaviors of Individuals Referred for Autism Spectrum Disorder Assessment

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Title: Structure of Restricted Repetitive Behaviors of Individuals Referred for Autism Spectrum Disorder Assessment
Language: English
Authors: Helen Kay Root, Monica M. Abdul-Chani, Zachary Enos Arnold, Jeremy J. Cottle, Timothy Hilty, Kristi Carter Guest, Sarah E. O'Kelley
Source: Journal of Autism and Developmental Disorders. 2026 56(1):100-109.
Availability: Springer. Available from: Springer Nature. One New York Plaza, Suite 4600, New York, NY 10004. Tel: 800-777-4643; Tel: 212-460-1500; Fax: 212-460-1700; e-mail: customerservice@springernature.com; Web site: https://link.springer.com/
Peer Reviewed: Y
Page Count: 10
Publication Date: 2026
Document Type: Journal Articles
Reports - Research
Descriptors: Behavior Problems, Symptoms (Individual Disorders), Autism Spectrum Disorders, Neurodevelopmental Disorders, Children, Child Behavior, Screening Tests
DOI: 10.1007/s10803-024-06536-7
ISSN: 0162-3257
1573-3432
Abstract: Purpose: Restricted and/or repetitive displays of behavior, interests, or activities (RRBs) are one of the core symptom domains of autism spectrum disorder (ASD). Current and past research indicates two 'clusters' of RRBs in children with ASD: repetitive sensorimotor (e.g., hand/finger and more complex motor mannerisms) and insistence on sameness (e.g., resistance to changes in the environment) behaviors. The current study aims to fill a gap by examining how RRBs may diverge in individuals with ASD and with other neurodevelopmental disorders (ONDD) in a clinical sample. Methods: A total of 558 individuals were seen at a tertiary care clinic for a comprehensive clinical assessment of ASD. The sample was split into ASD (n = 292 individuals) and ONDD (n = 266) groups based on clinical diagnosis. Exploratory factor analyses were conducted using Autism Diagnostic Interview-Revised (ADI-R) RRB item scores for the overall sample, the ASD group, and the ONDD group. Results: Exploratory factor analysis of ADI-R RRB items indicated a 2-factor solution for the full sample and ASD group. Items loaded onto two factors comprised of "Repetitive Sensorimotor" and "Insistence on Sameness" behaviors, consistent with previous literature. Results demonstrated a unique loading pattern for the non-ASD group, with items clustering into "Higher Order" (e.g., circumscribed interests) and "Lower Order" (e.g., hand and finger mannerisms) behaviors. Conclusion: The results of the current study may point towards using RRBs to guide screening of children who are referred for an ASD evaluation to better identify children who are at higher risk of having ASD.
Abstractor: As Provided
Entry Date: 2026
Accession Number: EJ1504730
Database: ERIC
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  Value: <anid>AN0191290297;aut01jan.26;2026Feb04.02:38;v2.2.500</anid> <title id="AN0191290297-1">Structure of Restricted Repetitive Behaviors of Individuals Referred for Autism Spectrum Disorder Assessment </title> <p>Purpose: Restricted and/or repetitive displays of behavior, interests, or activities (RRBs) are one of the core symptom domains of autism spectrum disorder (ASD). Current and past research indicates two 'clusters' of RRBs in children with ASD: repetitive sensorimotor (e.g., hand/finger and more complex motor mannerisms) and insistence on sameness (e.g., resistance to changes in the environment) behaviors. The current study aims to fill a gap by examining how RRBs may diverge in individuals with ASD and with other neurodevelopmental disorders (ONDD) in a clinical sample. Methods: A total of 558 individuals were seen at a tertiary care clinic for a comprehensive clinical assessment of ASD. The sample was split into ASD (n = 292 individuals) and ONDD (n = 266) groups based on clinical diagnosis. Exploratory factor analyses were conducted using Autism Diagnostic Interview-Revised (ADI-R) RRB item scores for the overall sample, the ASD group, and the ONDD group. Results: Exploratory factor analysis of ADI-R RRB items indicated a 2-factor solution for the full sample and ASD group. Items loaded onto two factors comprised of "Repetitive Sensorimotor" and "Insistence on Sameness" behaviors, consistent with previous literature. Results demonstrated a unique loading pattern for the non-ASD group, with items clustering into "Higher Order" (e.g., circumscribed interests) and "Lower Order" (e.g., hand and finger mannerisms) behaviors. Conclusion: The results of the current study may point towards using RRBs to guide screening of children who are referred for an ASD evaluation to better identify children who are at higher risk of having ASD.</p> <p>Keywords: Autism spectrum disorder; Restricted and repetitive behaviors; Factor analysis; Autism diagnostic interview-revised; Medical and Health Sciences Public Health and Health Services</p> <p>Copyright comment Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.</p> <p>Knowledge and awareness of autism spectrum disorder (ASD) has increased substantially over the past 60 years due to the increasing interest of researchers worldwide (Wolff, [<reflink idref="bib40" id="ref1">40</reflink>]). Criteria for a diagnosis, as outlined in the Diagnostic and Statistical Manual, Fifth Edition, Text Revision (DSM-5-TR) require deficits in social communication and interaction and the presence of restricted, repetitive behaviors, interests, or activities (American Psychiatric Association, [<reflink idref="bib1" id="ref2">1</reflink>]). While a majority of parents of children diagnosed with ASD report concerns about their child's development prior to 2 years of age (Kozlowski et al., [<reflink idref="bib11" id="ref3">11</reflink>]) and despite evidence of the stability of an ASD diagnosis at this age (Lord et al., [<reflink idref="bib16" id="ref4">16</reflink>]), the average age of diagnosis in the United States is around 4 years of age (Maenner et al., [<reflink idref="bib18" id="ref5">18</reflink>]) Due to this disparity, it is beneficial to look more closely at the symptom domains of ASD to examine how to promote earlier diagnosis.</p> <p>One of the two core symptom domains of ASD is the presence of restricted and/or repetitive patterns of behavior, interests, or activities (American Psychiatric Association, [<reflink idref="bib1" id="ref6">1</reflink>]) – broadly referred to as RRBs. RRBs include stereotyped or repetitive speech, motor movements, or use of objects; insistence on strict adherence to daily routines; extreme resistance to change; ritualized behavior; fixated interest of abnormal intensity or focus; and atypical reactivity to a range of sensory stimuli. These behaviors may characterize some of the initial presentations of ASD – often emerging before language development delays (Wolff et al., [<reflink idref="bib41" id="ref7">41</reflink>]). However, estimates have shown that approximately 16% of children diagnosed with ASD have behavioral difficulties cited as the area of first concern compared to almost 50% of concerns related to atypical language development (McConachie et al., [<reflink idref="bib20" id="ref8">20</reflink>]). Notably, RRBs are also seen in typical development (Evans et al., [<reflink idref="bib6" id="ref9">6</reflink>]; Leekam et al., [<reflink idref="bib13" id="ref10">13</reflink>]; Thelen, [<reflink idref="bib32" id="ref11">32</reflink>]; Wolff et al., [<reflink idref="bib41" id="ref12">41</reflink>]) and children with other neurodevelopmental disabilities (Berry et al., [<reflink idref="bib3" id="ref13">3</reflink>]), substantially increasing the difficulty parents face in identifying the level at which these behaviors warrant concern and/or consideration of an ASD diagnosis (Wolff et al., [<reflink idref="bib41" id="ref14">41</reflink>]).</p> <p>RRBs can be both developmentally appropriate and additive to learning. However, children with ASD have significantly greater frequency, amounts, and severity of such behaviors beginning prior to 12 months of age regardless of cognitive and adaptive abilities (Ozonoff et al., [<reflink idref="bib23" id="ref15">23</reflink>]; Wolff et al., [<reflink idref="bib41" id="ref16">41</reflink>]). Notably, research has demonstrated that the typical presentation of RRBs in ASD is dependent on age. Specifically, children with ASD tend to display repetitive motor movements including rocking, spinning, hand flapping, and unusual posturing, commonly thought of as "lower order" RRBs (Harrop et al., [<reflink idref="bib9" id="ref17">9</reflink>]; Militerni et al., [<reflink idref="bib21" id="ref18">21</reflink>]; Ozonoff et al., [<reflink idref="bib23" id="ref19">23</reflink>]; Richler et al., [<reflink idref="bib25" id="ref20">25</reflink>]; Wolff et al., [<reflink idref="bib41" id="ref21">41</reflink>]) in infancy. At 2 or 3 years of age, children with ASD display frequent repetitive movements involving their body or objects as well as unusual sensory preoccupations or interests. This pattern of increasing complexity continues into later childhood, as children at 7 to 11 years of age may display greater frequency of repetitive complex motor sequences (e.g., filling and emptying sequences, repetitive pretend play; (Militerni et al., [<reflink idref="bib21" id="ref22">21</reflink>]), although trajectories of change in RRBs are heterogeneous (Richler et al., [<reflink idref="bib25" id="ref23">25</reflink>]). Moreover intellectual ability appears to impact the complexity of RRBs in children with ASD, as those who have higher intellectual ability demonstrate more complex or "higher order" RRBs (i.e., circumscribed interests and unusual preoccupations; (Militerni et al., [<reflink idref="bib21" id="ref24">21</reflink>]). Using RRB-related items from the Autism Diagnostic Interview-Revised (ADI-R) – a gold-standard diagnostic instrument for ASD – many studies have provided evidence for the existence of two 'clusters' of RRBs (i.e., Repetitive Sensorimotor and Insistence on Sameness behaviors) in children with ASD across age range and abilities (Cuccaro et al., [<reflink idref="bib4" id="ref25">4</reflink>]; Lewis & Kim, [<reflink idref="bib14" id="ref26">14</reflink>]; Mooney et al., [<reflink idref="bib22" id="ref27">22</reflink>]; Richler et al., [<reflink idref="bib24" id="ref28">24</reflink>]; Szatmari et al., [<reflink idref="bib30" id="ref29">30</reflink>]; Turner, [<reflink idref="bib33" id="ref30">33</reflink>]). Repetitive Sensorimotor behaviors include hand, finger, and more complex motor mannerisms; the repetitive usage of parts or whole objects; and unusual sensory interests or aversions. Insistence on Sameness behaviors encompass ritualistic or compulsive behaviors; difficulties with change in daily routines; and resistance to changes in the environment. Another recent study suggested three possible factors, capturing these two proposed clusters while adding a factor related to Unusual or Circumscribed Interests (Uljarević et al., [<reflink idref="bib34" id="ref31">34</reflink>]), whereas a recent meta-analysis of factor correlations across measures suggested the presence of eight specific factors in the RRB domain (Uljarević et al., [<reflink idref="bib35" id="ref32">35</reflink>]). Recently, an exploratory factor analysis using the ADI-R with a preschool-age community-based research sample identified an additional novel stereotyped speech factor (Hiruma et al., [<reflink idref="bib10" id="ref33">10</reflink>]) and was the first to examine differences in factor structures between individuals with an ASD diagnosis and individuals without an ASD diagnosis. However, the non-ASD sample was small, especially compared to the larger ASD sample, and the findings regarding the non-ASD factor structure were ill-defined as the factors were difficult to conceptualize. Despite an increased interest in characterizing RRBs of individuals with ASD, there are still gaps in the literature, including how RRBs may present in clinical samples. No known prior studies have examined a clinical sample to assess how RRBs may diverge in individuals who receive an ASD diagnosis as opposed to other neurodevelopmental disabilities (ONDD). Moreover, inclusion of school-age children is imperative for characterizing RRBs across a crucial age range when diagnosis frequently takes place (Mandell et al., [<reflink idref="bib19" id="ref34">19</reflink>]). Better understanding of these behavior profiles may aid in earlier detection, screening, and diagnosis of ASD.</p> <hd id="AN0191290297-2">Current Study</hd> <p>The current study aimed to characterize the RRBs of children referred to a tertiary care clinic for an ASD evaluation. Specifically, the current study examines the structure of RRBs in a sample of children who have a wide range of developmental concerns in addition to a core referral concern of possible ASD. Furthermore, this study assesses the structure of RRBs exhibited by individuals who receive an ASD diagnosis versus those who are determined not to have ASD. Given the wealth of literature regarding the two-factor structure of RRBs on the ADI-R and that all individuals in the current sample were referred due to a concern of possible ASD, it was hypothesized that the RRBs of the overall sample would cluster into two factors: Repetitive Sensorimotor and Insistence on Sameness. Additionally, RRBs were hypothesized to cluster differently between the ASD and non-ASD groups – with RRBs of the ASD group clustering into the same two factors as the overall sample and a novel cluster for the non-ASD group.</p> <hd id="AN0191290297-3">Methods</hd> <p></p> <hd id="AN0191290297-4">Participants</hd> <p>The overall sample included 558 individuals seen at a tertiary care clinic for a comprehensive clinical assessment of ASD. While all individuals were referred to the tertiary care clinic due to concerns of possible ASD, 292 individuals (52%) received an ASD diagnosis and 266 (48%) were determined to have ONDD (e.g., intellectual disability, language disorder, ADHD). Groups were assigned based on presence (ASD) or absence (ONDD) of ASD diagnosis. To be included in the current study, an ADI-R had to have been completed during the comprehensive assessment and the participants had to be younger than 10 years. Ten years of age was chosen as a cutoff for the current sample due to changes in the ADI-R algorithm after the age of 10 and the ASD clinic serving largely preschool and school-aged children under the age of 10. Participant characteristics can be found in Table 1. The racial composition of the sample was as follows: 58.0% White, 24.2% Black, 0.36% Asian, 0.36% other race, and 12.4% unknown. 4.5% of the sample identified as Hispanic. The sample consisted of 19.0% females. The average age was 4.62 years (<emph>SD</emph> = 1.99 years), with a range from 1 year 5 months to 9 years 11 months. Cognitive scores (<emph>M</emph> = 78.21, <emph>SD</emph> = 18.5) and adaptive scores (<emph>M</emph> = 69.7, <emph>SD</emph> = 12.3) did not differ between groups.</p> <p>Table 1 Participant characteristics</p> <p> <ephtml> <table rules="groups"><thead><tr><th align="left"><p>Demographics</p></th><th align="left"><p>Overall</p><p>N = 558</p></th><th align="left"><p>ASD</p><p>N = 292</p></th><th align="left"><p>ONDD</p><p>N = 266</p></th><th align="left"><p>p-value</p></th></tr></thead><tbody><tr><td align="left"><p>Gender (% Females)</p></td><td align="left"><p>19.0%</p></td><td align="left"><p>17.1%</p></td><td align="left"><p>21.1%</p></td><td align="left"><p><italic>n.s.</italic></p></td></tr><tr><td align="left"><p>Race/Ethnicity</p></td><td align="left" /><td align="left" /><td align="left" /><td align="left" /></tr><tr><td align="left"><p> White (%)</p></td><td align="left"><p>58.0%</p></td><td align="left"><p>53.6%</p></td><td align="left"><p>62.8%</p></td><td align="left"><p><italic>n.s.</italic></p></td></tr><tr><td align="left"><p> Black (%)</p></td><td align="left"><p>24.2%</p></td><td align="left"><p>26.1%</p></td><td align="left"><p>22.2%</p></td><td align="left"><p><italic>n.s.</italic></p></td></tr><tr><td align="left"><p> Asian (%)</p></td><td align="left"><p>0.36%</p></td><td align="left"><p>0.34%</p></td><td align="left"><p>0.38%</p></td><td align="left"><p><italic>n.s.</italic></p></td></tr><tr><td align="left"><p> Hispanic/Latinx</p></td><td align="left"><p>4.5%</p></td><td align="left"><p>5.2%</p></td><td align="left"><p>3.8%</p></td><td align="left"><p><italic>n.s.</italic></p></td></tr><tr><td align="left"><p> Other (%)</p></td><td align="left"><p>0.36%</p></td><td align="left"><p>0.34%</p></td><td align="left"><p>0.38%</p></td><td align="left"><p><italic>n.s.</italic></p></td></tr><tr><td align="left"><p> Unknown (%)</p></td><td align="left"><p>12.4%</p></td><td align="left"><p>14.1%</p></td><td align="left"><p>10.5%</p></td><td align="left"><p><italic>n.s.</italic></p></td></tr><tr><td align="left"><p>Age (years)</p><p><italic>M (SD)</italic></p></td><td align="left"><p>4.62</p><p>(1.99)</p></td><td align="left"><p>4.57</p><p>(2.01)</p></td><td align="left"><p>4.67</p><p>(1.97)</p></td><td align="left"><p><italic>n.s.</italic></p></td></tr><tr><td align="left"><p> Clinical Characteristics</p></td><td align="left" /><td align="left" /><td align="left" /><td align="left" /></tr><tr><td align="left"><p>ADOS Comparison Score</p><p><italic>M (SD)</italic></p></td><td align="left"><p>5.15</p><p>(2.73)</p></td><td align="left"><p>6.95</p><p>(1.87)</p></td><td align="left"><p>3.17</p><p>(2.07)</p></td><td align="left"><p><italic>p</italic> < 0.001</p></td></tr><tr><td align="left"><p>Cognitive Standard Score</p><p><italic>M (SD)</italic></p></td><td align="left"><p>78.22</p><p>(18.57)</p></td><td align="left"><p>76.08</p><p>(20.18)</p></td><td align="left"><p>79.84</p><p>(17.13)</p></td><td align="left"><p><italic>n.s.</italic></p></td></tr><tr><td align="left"><p>Adaptive Standard Score</p><p><italic>M (SD)</italic></p></td><td align="left"><p>69.65</p><p>(12.31)</p></td><td align="left"><p>68.9</p><p>(12.8)</p></td><td align="left"><p>70.4</p><p>(11.8)</p></td><td align="left"><p><italic>n.s.</italic></p></td></tr></tbody></table> </ephtml> </p> <hd id="AN0191290297-5">Procedure</hd> <p>Procedures for this study were approved by the Institutional Review Board. Children with a range of developmental concerns were seen at a tertiary care clinic to determine whether a diagnosis of ASD was appropriate. Children received a comprehensive multi-disciplinary evaluation from disciplines appropriate to their referral concern (e.g., audiology, optometry, speech/language pathology, occupational therapy, pediatrics, nutrition, social work, psychology) between 2006 and 2018. At a minimum, all children in the current sample received a comprehensive ASD evaluation led by a psychologist which included an Autism Diagnostic Observation Schedule (ADOS) or Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) and Autism Diagnostic Interview-Revised (ADI-R). Two clinicians at the clinic were independently research-reliable on both measures and the remainder of clinicians who administered the ADOS-2 and ADI-R were site-reliable. All clinicians had attended clinical ADOS training, and many had attended research reliability training but did not complete independent reliability. Following the comprehensive clinical evaluation, licensed clinical professionals made a consensus diagnosis regarding the presence or absence of ASD based on all available information (e.g., current testing, school records, medical history). This variable was utilized to create two groups in the current study, those who received an ASD diagnosis (ASD) and those who presented with an ONDD. A breakdown of the diagnostic categories included in the ONDD group can be found in Table 2.</p> <p>Table 2 Common diagnoses in the ONDD group (N = 251)</p> <p> <ephtml> <table rules="groups"><thead><tr><th align="left"><p>Variable</p></th><th align="left"><p>n (%)</p></th></tr></thead><tbody><tr><td align="left"><p>ADHD</p></td><td align="left"><p>19 (7.6%)</p></td></tr><tr><td align="left"><p>Global/Mixed Developmental Delays</p></td><td align="left"><p>41 (16.3%)</p></td></tr><tr><td align="left"><p>Intellectual Disability</p></td><td align="left"><p>7 (2.8%)</p></td></tr><tr><td align="left"><p>Anxiety Disorders</p></td><td align="left"><p>7 (2.8%)</p></td></tr><tr><td align="left"><p>Language Disorders</p></td><td align="left"><p>45 (17.9%)</p></td></tr><tr><td align="left"><p>Unknown</p></td><td align="left"><p>132 (52.6%)</p></td></tr></tbody></table> </ephtml> </p> <p> <emph>Note</emph> Some participants were diagnosed with 2 or more NDDs or other NDDs that were less common in this sample. For 132 participants, diagnoses were missing or unreported due changes in how clinical data was extracted over the years included in this study (i.e., non-ASD diagnoses were not captured consistently)</p> <p>Data from comprehensive clinical evaluations were collected via retrospective chart review. Data availability varied from child to child as the assessment batteries were chosen by clinicians based on referral concerns and other factors (e.g., time available for the assessment, patient fatigue). The chart review and data extraction processes were systematic in prioritizing information gathered from the reports generated by clinicians from the university's tertiary care clinic evaluation. Additional sources, in order of priority, included medical records, caregiver report on intake paperwork, school reports, and reports from outside evaluations. All variables had consensus-operational definitions and lab members (i.e., graduate and undergraduate students) were trained to 95% reliability for collection of data. In addition, 10% of all data collection from chart review and data entry into the database were checked for reliability. If discrepancies were identified, a code book of previous consensus decisions was reviewed and there was discussion with lab members and faculty mentors to achieve consensus.</p> <hd id="AN0191290297-6">Materials</hd> <p></p> <hd id="AN0191290297-7">Autism Diagnostic Interview-Revised (ADI-R)</hd> <p>The ADI-R is a semi-structured, standardized interview conducted by clinicians with caregiver(s) of individuals with ASD (Rutter et al., [<reflink idref="bib28" id="ref35">28</reflink>]). It is considered a gold standard measure for diagnosing ASD, particularly in combination with the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2). The ADI-R consists of 93 items focusing on three domains of functioning: Language/Communication, Reciprocal Social Interactions, and Restricted, Repetitive, and Stereotyped Behaviors and Interests. Coefficient alphas for internal consistency, test-retest reliability, and inter-rater reliability for the ADI-R are 0.80 or greater (Lord et al., [<reflink idref="bib15" id="ref36">15</reflink>]). Items are scored by a clinician on a scale of 0 to 3 based on parental description of the presence and severity of given behaviors, with a score of 0 meaning the behavior is not present and 3 meaning it is present and severely impacts daily functioning. For most items, there is a "current" and "ever" score, with the current score examining present functioning and the ever score focusing on the child's 4th year of life, when applicable. Because many of the participants in the current study were under five years of age, only the "current" scores were utilized for the entire sample. The following algorithm items for RRBs were included in analyses: Stereotyped Utterance and Delayed Echolalia (Item 33), Verbal Rituals (Item 39), Unusual Preoccupations (Item 67), Circumscribed Interests (Item 68), Repetitive Use of Objects or Interest in Parts of Objects (Item 69), Compulsions/Rituals (Item 70), Unusual Sensory Interests (Item 71), Hand and Finger Mannerisms (Item 77), and Other Complex Mannerisms or Stereotyped Body Movements (Item 78). Descriptives and a correlation matrix for ADI-R items are described in Tables 3 and 4, respectively.</p> <p>Table 3 Descriptives for ADI-R items</p> <p> <ephtml> <table rules="groups"><thead><tr><th align="left"><p>Item</p></th><th align="left"><p>n</p></th><th align="left"><p>M (SD)</p></th><th align="left"><p>Transformed M (SD)</p></th></tr></thead><tbody><tr><td align="left"><p>Stereotyped Utterances and Delayed Echolalia</p></td><td align="left"><p>212</p></td><td align="left"><p>0.92 (0.79)</p></td><td align="left"><p>0.76 (0.58)</p></td></tr><tr><td align="left"><p>Verbal Rituals</p></td><td align="left"><p>208</p></td><td align="left"><p>0.41 (0.72)</p></td><td align="left"><p>0.34 (0.55)</p></td></tr><tr><td align="left"><p>Unusual Preoccupations</p></td><td align="left"><p>428</p></td><td align="left"><p>0.28 (0.59)</p></td><td align="left"><p>0.24 (0.47)</p></td></tr><tr><td align="left"><p>Circumscribed Interests</p></td><td align="left"><p>370</p></td><td align="left"><p>0.64 (0.90)</p></td><td align="left"><p>0.50 (0.63)</p></td></tr><tr><td align="left"><p>Repetitive Use of Objects or Interest in Parts of Objects</p></td><td align="left"><p>424</p></td><td align="left"><p>1.09 (0.89)</p></td><td align="left"><p>0.87 (0.58)</p></td></tr><tr><td align="left"><p>Compulsions/Rituals</p></td><td align="left"><p>428</p></td><td align="left"><p>0.53 (0.88)</p></td><td align="left"><p>0.40 (0.60)</p></td></tr><tr><td align="left"><p>Unusual Sensory Interests</p></td><td align="left"><p>426</p></td><td align="left"><p>0.67 (0.65)</p></td><td align="left"><p>0.62 (0.54)</p></td></tr><tr><td align="left"><p>Hand and Finger Mannerisms</p></td><td align="left"><p>428</p></td><td align="left"><p>0.53 (0.80)</p></td><td align="left"><p>0.43 (0.59)</p></td></tr><tr><td align="left"><p>Other Complex Mannerisms or Stereotyped Body Movements</p></td><td align="left"><p>421</p></td><td align="left"><p>0.59 (0.81)</p></td><td align="left"><p>0.48 (0.60)</p></td></tr></tbody></table> </ephtml> </p> <p>Table 4 Correlation matrix of ADI-R items</p> <p> <ephtml> <table rules="groups"><thead><tr><th align="left"><p>Item</p></th><th align="left"><p>Stereo_Echo</p></th><th align="left"><p>Verb_Rit</p></th><th align="left"><p>Unu_Preocc</p></th><th align="left"><p>Circ_Int</p></th><th align="left"><p>Rep_Obj</p></th><th align="left"><p>Comp_Rit</p></th><th align="left"><p>Unu_Sense</p></th><th align="left"><p>Hand_Finger</p></th><th align="left"><p>Other_Comp</p></th></tr></thead><tbody><tr><td align="left"><p>Stereotyped Utterances and Delayed Echolalia</p></td><td align="left"><p>1</p></td><td align="left" /><td align="left" /><td align="left" /><td align="left" /><td align="left" /><td align="left" /><td align="left" /><td align="left" /></tr><tr><td align="left"><p>Verbal Rituals</p></td><td align="left"><p>0.341**</p></td><td align="left"><p>1</p></td><td align="left" /><td align="left" /><td align="left" /><td align="left" /><td align="left" /><td align="left" /><td align="left" /></tr><tr><td align="left"><p>Unusual Preoccupations</p></td><td align="left"><p>0.025</p></td><td align="left"><p>0.227**</p></td><td align="left"><p>1</p></td><td align="left" /><td align="left" /><td align="left" /><td align="left" /><td align="left" /><td align="left" /></tr><tr><td align="left"><p>Circumscribed Interests</p></td><td align="left"><p>0.225**</p></td><td align="left"><p>0.167*</p></td><td align="left"><p>0.038</p></td><td align="left"><p>1</p></td><td align="left" /><td align="left" /><td align="left" /><td align="left" /><td align="left" /></tr><tr><td align="left"><p>Repetitive Use of Objects or Interests in Parts of Objects</p></td><td align="left"><p>0.227**</p></td><td align="left"><p>0.188**</p></td><td align="left"><p>0.058</p></td><td align="left"><p>0.039</p></td><td align="left"><p>1</p></td><td align="left" /><td align="left" /><td align="left" /><td align="left" /></tr><tr><td align="left"><p>Compulsions/Rituals</p></td><td align="left"><p>0.174*</p></td><td align="left"><p>0.260**</p></td><td align="left"><p>0.181**</p></td><td align="left"><p>0.197**</p></td><td align="left"><p>0.119*</p></td><td align="left"><p>1</p></td><td align="left" /><td align="left" /><td align="left" /></tr><tr><td align="left"><p>Unusual Sensory Interests</p></td><td align="left"><p>0.232**</p></td><td align="left"><p>0.115</p></td><td align="left"><p>0.128**</p></td><td align="left"><p>0.004</p></td><td align="left"><p>0.344**</p></td><td align="left"><p>0.066</p></td><td align="left"><p>1</p></td><td align="left" /><td align="left" /></tr><tr><td align="left"><p>Hand and Finger Mannerisms</p></td><td align="left"><p>0.238**</p></td><td align="left"><p>0.104</p></td><td align="left"><p>0.042</p></td><td align="left"><p>0.002</p></td><td align="left"><p>0.278**</p></td><td align="left"><p>0.092</p></td><td align="left"><p>0.265**</p></td><td align="left"><p>1</p></td><td align="left" /></tr><tr><td align="left"><p>Other Complex Mannerisms or Stereotyped Body Movements</p></td><td align="left"><p>0.258**</p></td><td align="left"><p>0.082</p></td><td align="left"><p>0.118*</p></td><td align="left"><p>0.035</p></td><td align="left"><p>0.308**</p></td><td align="left"><p>0.099*</p></td><td align="left"><p>0.281**</p></td><td align="left"><p>0.328**</p></td><td align="left"><p>1</p></td></tr></tbody></table> </ephtml> </p> <p> <emph>Note</emph> *<emph>p</emph> < 0.05, **<emph>p</emph> < 0.01</p> <hd id="AN0191290297-8">Autism Diagnostic Observation Schedule (ADOS-G) and Autism Diagnostic Observation Schedule, S...</hd> <p>The ADOS-G and ADOS-2 are play-based assessments designed to observe social and communication behaviors associated with an ASD diagnosis (Lord et al., [<reflink idref="bib17" id="ref37">17</reflink>]). There are 5 modules of the ADOS-2, administered based on age (Toddler Module) or language ability (Modules 1–4). Each module provides social communication and RRB domain scores. The Toddler Module provides a level of concern for ASD, while Modules 1–4 provide a comparison score between 1 and 10 with higher scores indicating greater ASD symptom severity. The ADOS-G and ADOS-2 was used to supplement determination of an ASD diagnosis.</p> <hd id="AN0191290297-9">Cognitive and Adaptive Measures</hd> <p>Due to factors such as age and level of functioning, children were assessed using various cognitive and adaptive measures. Thus, standard scores (<emph>M</emph> = 100, <emph>SD</emph> = 10) from these measures were collapsed into a single variable for cognitive ability and a single variable for adaptive skills. Cognitive assessments included: Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III); Differential Ability Scales, Second Edition (DAS-II); Leiter International Performance Scale, Third Edition (Leiter-3); Stanford-Binet Intelligence Scales, Fifth Edition (SB-5); Wechsler Abbreviated Scale of Intelligence, First Edition (WASI) and Second Edition (WASI-II); and Wechsler Intelligence Scale for Children, Fourth Edition (WISC-IV) and Fifth Edition (WISC-V) (Bayley, [<reflink idref="bib2" id="ref38">2</reflink>]; Elliott, [<reflink idref="bib5" id="ref39">5</reflink>]; Roid, [<reflink idref="bib26" id="ref40">26</reflink>]; Roid et al., [<reflink idref="bib27" id="ref41">27</reflink>]; Wechsler, [<reflink idref="bib36" id="ref42">36</reflink>], [<reflink idref="bib37" id="ref43">37</reflink>], [<reflink idref="bib38" id="ref44">38</reflink>], [<reflink idref="bib39" id="ref45">39</reflink>]). Adaptive measures included: Vineland Adaptive Behavior Scales, Second Edition (Vineland-II) and Third Edition (Vineland-3), and Adaptive Behavior Assessment System, Third Edition (ABAS-3) (Harrison & Oakland, [<reflink idref="bib8" id="ref46">8</reflink>]; Sparrow et al., [<reflink idref="bib29" id="ref47">29</reflink>]).</p> <hd id="AN0191290297-10">Data Analysis</hd> <p>Three exploratory factor analyses were conducted on the nine RRB items of the ADI-R within the overall sample, the ASD group, and the ONDD group. Maximum likelihood analyses with Varimax rotation were utilized to identify factors. A value of 0.3 was used as cutoff for factor loadings. Eigenvalues, scree plots, and follow-up sensitivity analysis contributed to determining the number of factors to maintain.</p> <p>Due to assumption violations, data were transformed using the square root transformation. Following transformation of data, analyses were initially conducted with Principal Components Analysis and Oblimin rotation. Given low factor correlations (r's < 0.2), analyses were re-run using Varimax rotation, which improved factor correlations (r's > 0.3). Analyses indicated a two-factor solution, with the exception of Item 67 which did not load onto either factor; however, squared multiple correlations were all equal to 1. Maximum Likelihood analyses with Varimax rotation were conducted, which improved the squared multiple correlations and still yielded a two-factor solution. Item 67 still did not load on either of the factors, so it was removed from analyses and analyses were rerun.</p> <p>Chi square analyses revealed a significant difference on ASD diagnosis (p's < 0.05) between groups who did and did not have missingness on all RRB items. Children with ASD were more likely to have missingness on items 33 and 39, while children without ASD were more likely to have missingness on items 67, 68, 69, 70, 71, 77, and 78. Chi square analyses revealed no significant differences between missingness groups on gender (p's > 0.05). Independent samples t-tests revealed a significant difference on age between groups who did and did not have missingness on all items. Analyses indicated that younger children were more likely to have missingness. Sensitivity analysis was run using pairwise and listwise deletion which produced comparable results.</p> <hd id="AN0191290297-11">Results</hd> <p></p> <hd id="AN0191290297-12">Preliminary Analysis</hd> <p>The assumption of multivariate normality was met for all items except for Item 67: Unusual Preoccupations. Upon examination of this item, there was significant kurtosis (4.46) and positive skewness (2.20), however, given the rarity of this behavior in younger children, it was found to be clinically relevant data. Although univariate outliers were present for three items (Verbal Rituals, Unusual Preoccupations, Unusual Sensory Interests), the normality violations and outliers were largely due to individuals who had scores of 3. As the average age of the sample was 4.62 years, the low number of individuals with a score of 3, which indicates frequent and severe RRBs, is unsurprising, yet the information was still valuable clinically and therefore was not removed. Given the violations of the normality, linearity, and outliers assumptions, data was transformed using the square root transformation (Tabachnick et al., [<reflink idref="bib31" id="ref48">31</reflink>]). Assumptions were retested and all were met.</p> <hd id="AN0191290297-13">Main Analysis</hd> <p>Exploratory factor analysis using Maximum Likelihood and Varimax rotation yielded several latent factors for the overall sample (see Table 5). Analyses yielded two eigenvalues greater than one with all items included, as well as when Unusual Preoccupations was removed. Scree plot analysis indicated a break between factors 2 and 3, suggesting a two-factor solution. The rotated factor matrix also indicated a two-factor solution. Sensitivity analysis of Maximum Likelihood and Principal Components Analysis revealed comparable results. A two-factor solution is presented, due to moderate factor loadings and interpretability of results.</p> <p>Table 5 Factor loadings for the entire sample</p> <p> <ephtml> <table rules="groups"><thead><tr><th align="left"><p>Item</p></th><th align="left"><p>Factor 1:</p><p>Repetitive Sensorimotor</p></th><th align="left"><p>Factor 2:</p><p>Insistence on Sameness</p></th></tr></thead><tbody><tr><td align="left"><p>Stereotyped Utterances and Delayed Echolalia</p></td><td align="left"><p>0.364</p></td><td align="left"><p>0.584</p></td></tr><tr><td align="left"><p>Verbal Rituals</p></td><td align="left" /><td align="left"><p>0.655</p></td></tr><tr><td align="left"><p>Circumscribed Interests</p></td><td align="left" /><td align="left"><p>0.693</p></td></tr><tr><td align="left"><p>Compulsions/Rituals</p></td><td align="left" /><td align="left"><p>0.623</p></td></tr><tr><td align="left"><p>Repetitive Use of Objects or Interest in Parts of Objects</p></td><td align="left"><p>0.656</p></td><td align="left" /></tr><tr><td align="left"><p>Unusual Sensory Interests</p></td><td align="left"><p>0.674</p></td><td align="left" /></tr><tr><td align="left"><p>Hand and Finger Mannerisms</p></td><td align="left"><p>0.655</p></td><td align="left" /></tr><tr><td align="left"><p>Other Complex Mannerisms/Stereotyped Body Movements</p></td><td align="left"><p>0.678</p></td><td align="left" /></tr></tbody></table> </ephtml> </p> <p> <emph>Note</emph> Item 67 was removed from analyses due to failing to load onto either factor</p> <p>The two-factor rotated solution accounted for 45.1% of variance. Factor 1 accounted for 24.4% of variance and included Repetitive Use of Objects, Unusual Sensory Interests, Hand/Finger Mannerism, and Other Complex Mannerisms or Stereotyped Body Movements. This factor encompasses "Repetitive Sensorimotor" RRBs. Factor 2 accounted for 20.8% of variance and consisted of Stereotyped Utterances and Delayed Echolalia, Verbal Rituals, Circumscribed Interests, and Compulsions/Rituals. This factor encompasses "Insistence on Sameness" RRBs. Stereotyped Utterances and Delayed Echolalia had a split-loading between Factors 1 (0.364) and 2 (0.584), however, it had a higher loading on Factor 2 and was conceptually more related.</p> <p>To examine the structure of RRBs within the two groups, exploratory factor analysis was run separately for the ASD and non-ASD groups. Initially, Maximum Likelihood analyses with Varimax rotation were used while requesting a two-factor solution, as found in the overall sample. For the ASD group, two eigenvalues were greater than 1.0, scree plot analysis indicated a break at Factor 3, and interpretability suggested the same two-factor solution as in the larger sample (Table 6), with the exception of Compulsions/Rituals, which did not load on either factor. Factor 1, "Repetitive Sensorimotor", accounted for 15.8% of variance and included Repetitive Use of Objects, Unusual Sensory Interests, Hand/Finger Mannerism, Other Complex Mannerisms or Stereotyped Body Movements. Factor 2, "Insistence on Sameness", accounted for 9.63% of variance and consisted of Stereotyped Utterances and Delayed Echolalia, Verbal Rituals, and Circumscribed Interests. There were no items with split-loadings. Sensitivity analysis with Principal Components Analysis yielded comparable results.</p> <p>Table 6 Factor loadings for the ASD Group</p> <p> <ephtml> <table rules="groups"><thead><tr><th align="left"><p>Item</p></th><th align="left"><p>Factor 1:</p><p>Repetitive Sensorimotor</p></th><th align="left"><p>Factor 2:</p><p>Insistence on Sameness</p></th></tr></thead><tbody><tr><td align="left"><p>Stereotyped Utterances and Delayed Echolalia</p></td><td align="left" /><td align="left"><p>0.414</p></td></tr><tr><td align="left"><p>Verbal Rituals</p></td><td align="left" /><td align="left"><p>0.415</p></td></tr><tr><td align="left"><p>Circumscribed Interests</p></td><td align="left" /><td align="left"><p>0.560</p></td></tr><tr><td align="left"><p>Repetitive Use of Objects or Interest in Parts of Objects</p></td><td align="left"><p>0.626</p></td><td align="left" /></tr><tr><td align="left"><p>Unusual Sensory Interests</p></td><td align="left"><p>0.570</p></td><td align="left" /></tr><tr><td align="left"><p>Hand and Finger Mannerisms</p></td><td align="left"><p>0.398</p></td><td align="left" /></tr><tr><td align="left"><p>Other Complex Mannerisms/Stereotyped Body Movements</p></td><td align="left"><p>0.464</p></td><td align="left" /></tr></tbody></table> </ephtml> </p> <p> <emph>Note</emph> Items 67 and 70 were removed from analyses due to failing to load onto either factor</p> <p>For the non-ASD group, when two factors were requested, two eigenvalues were greater than 1.0, scree plot analysis indicated a break between factor 2 and 3, and factor loadings suggested one to two factors. However, the factors were not similar to the factors found for the overall sample, so exploratory factor analysis using Maximum Likelihood and Varimax rotation was conducted. Repetitive Use of Objects and Unusual Sensory Interests did not load onto a factor, so they were removed from analyses and analyses were re-run. Analyses revealed three eigenvalues greater than 1.0, scree plot analyses indicated three factors, and factor loadings also indicated the presence of three factors (Table 7). Factor 1 accounted for 15.2% of variance and was made up of Unusual Preoccupations. Factor 2 accounted for 14.9% of variance and was made up of Stereotyped Utterances and Delayed Echolalia, Verbal Rituals, Circumscribed Interests, and Compulsions/Rituals. The items making up these factors are all those considered to be "Higher Order" RRBs and are typically seen in older individuals (Harrop et al., [<reflink idref="bib9" id="ref49">9</reflink>]; Militerni et al., [<reflink idref="bib21" id="ref50">21</reflink>]; Ozonoff et al., [<reflink idref="bib23" id="ref51">23</reflink>]; Richler et al., [<reflink idref="bib25" id="ref52">25</reflink>]; Wolff et al., [<reflink idref="bib41" id="ref53">41</reflink>]) and those with higher intellectual ability (Militerni et al., [<reflink idref="bib21" id="ref54">21</reflink>]). Factor 3 accounted for 10.2% of variance and was made up of Hand/Finger Mannerisms and Other Complex Mannerisms or Stereotyped Body Movements. The items contributing to these factors are considered "Lower Order" RRBs and are typically seen in younger individuals (Harrop et al., [<reflink idref="bib9" id="ref55">9</reflink>]; Militerni et al., [<reflink idref="bib21" id="ref56">21</reflink>]; Ozonoff et al., [<reflink idref="bib23" id="ref57">23</reflink>]; Richler et al., [<reflink idref="bib25" id="ref58">25</reflink>]; Wolff et al., [<reflink idref="bib41" id="ref59">41</reflink>]) and those with lower intellectual ability (Militerni et al., [<reflink idref="bib21" id="ref60">21</reflink>]). There were no items with split-loadings. When Unusual Preoccupations was removed, Factors 2 and 3 remained the same. Due to this item's high and unique loading, the Unusual Preoccupations item, and therefore Factor 1, were retained.</p> <p>Table 7 Factor loadings for the ONDD Group</p> <p> <ephtml> <table rules="groups"><thead><tr><th align="left"><p>Item</p></th><th align="left"><p>Factor 1:</p><p>Unusual Preoccupations</p></th><th align="left"><p>Factor 2:</p><p>Higher Order RRBs</p></th><th align="left"><p>Factor 3:</p><p>Lower Order RRBs</p></th></tr></thead><tbody><tr><td align="left"><p>Unusual Preoccupations</p></td><td align="left"><p>0.995</p></td><td align="left" /><td align="left" /></tr><tr><td align="left"><p>Stereotyped Utterances and Delayed Echolalia</p></td><td align="left" /><td align="left"><p>0.493</p></td><td align="left" /></tr><tr><td align="left"><p>Verbal Rituals</p></td><td align="left" /><td align="left"><p>0.531</p></td><td align="left" /></tr><tr><td align="left"><p>Circumscribed Interests</p></td><td align="left" /><td align="left"><p>0.439</p></td><td align="left" /></tr><tr><td align="left"><p>Compulsions/Rituals</p></td><td align="left" /><td align="left"><p>0.553</p></td><td align="left" /></tr><tr><td align="left"><p>Hand and Finger Mannerisms</p></td><td align="left" /><td align="left" /><td align="left"><p>0.331</p></td></tr><tr><td align="left"><p>Other Complex Mannerisms/Stereotyped Body Movements</p></td><td align="left" /><td align="left" /><td align="left"><p>0.730</p></td></tr></tbody></table> </ephtml> </p> <p> <emph>Note</emph> Items 69 and 71 were removed from analyses due to failing to load onto either factor</p> <hd id="AN0191290297-14">Discussion</hd> <p>The current exploratory factor analysis of the ADI-R RRB subscale is one of the first to analyze the RRB clusters in a clinical sample of children referred for a comprehensive ASD evaluation. The exploratory factor analysis of children referred for an ASD evaluation indicated the presence of two factors of RRBs, Repetitive Sensorimotor and Insistence on Sameness. These results confirm that children in this clinically derived sample exhibit the same clusters of RRBs as previous literature had suggested (Cuccaro et al., [<reflink idref="bib4" id="ref61">4</reflink>]; Lewis & Kim, [<reflink idref="bib14" id="ref62">14</reflink>]; Richler et al., [<reflink idref="bib25" id="ref63">25</reflink>]; Szatmari et al., [<reflink idref="bib30" id="ref64">30</reflink>]; Turner, [<reflink idref="bib33" id="ref65">33</reflink>]). A recent literature review also found a two-factor model of RRBs (e.g., Insistence of Sameness and Repetitive Motor Behaviors) across ASD and non-ASD populations (Uljarević et al., [<reflink idref="bib35" id="ref66">35</reflink>]). Of note, unusual preoccupations did not load onto either factor. However, this may be due to the young age of the current sample, as unusual preoccupations are seen more frequently in children who are older, verbal, and have greater intellectual ability (Militerni et al., [<reflink idref="bib21" id="ref67">21</reflink>]). These results suggest that clinicians should consider a child's age when attempting to identify RRBs in children with ONDDs, as RRBs may progress and change throughout the course of development (Harrop et al., [<reflink idref="bib9" id="ref68">9</reflink>]; Militerni et al., [<reflink idref="bib21" id="ref69">21</reflink>]; Ozonoff et al., [<reflink idref="bib23" id="ref70">23</reflink>]; Richler et al., [<reflink idref="bib25" id="ref71">25</reflink>]; Wolff et al., [<reflink idref="bib41" id="ref72">41</reflink>]). While there was a range of missingness on the ADI-R RRB items, items regarding verbal abilities, Item 33: Stereotyped Utterances and Delayed Echolalia and Item 39: Verbal Rituals, had the highest level of missingness. The level of missingness across those items is unsurprising, since it is likely that a large percentage of the children did not have sufficient verbal abilities for these questions to be asked. Therefore, future conceptualizations and efforts to recognize RRBs across children with ONDDs should consider their language abilities and how RRBs may manifest differently across language capabilities.</p> <p>When split into groups, children with ASD exhibited the same two factor structure of RRBs as the overall sample, Repetitive Sensorimotor and Insistence on Sameness. The only difference was that Insistence on Sameness no longer included Item 70, which measures Compulsions and Rituals. One explanation for Item 70 dropping from the model is that Compulsions and Rituals are considered a "higher order" RRB. As previously discussed, "higher order" RRBs are more typical in populations that are older, verbal, and have higher intellectual abilities (Harrop et al., [<reflink idref="bib9" id="ref73">9</reflink>]; Militerni et al., [<reflink idref="bib21" id="ref74">21</reflink>]); Ozonoff et al., [<reflink idref="bib23" id="ref75">23</reflink>]; Richler et al., [<reflink idref="bib25" id="ref76">25</reflink>]; Wolff et al., [<reflink idref="bib41" id="ref77">41</reflink>]). Therefore, the current results should be interpreted within the scope of a younger and less verbal ASD population than what was analyzed in previous studies.</p> <p>The exploratory factor analysis of children with ONDDs exhibited a distinct RRB profile. Specifically, children with ONDDs were found to have three factors of RRBs: Unusual Preoccupations, "Higher Order" (e.g., circumscribed interests, verbal rituals) and "Lower Order" (e.g., hand/finger mannerisms) behaviors. The Unusual Preoccupations factor should be analyzed with caution since the item was found to violate multivariate normality. However, since the ADI-R only measures severity on a 4-point scale and circumscribed interests are rarer in younger children due to the cognitive demands of interests (Militerni et al., [<reflink idref="bib21" id="ref78">21</reflink>]), this construct should be studied and scrutinized in older samples. Additionally, repetitive use of objects and unusual sensory interests did not load onto either factor for children with ONDDs. This suggests that children with ONDDs who are referred for an ASD evaluation but are not subsequently diagnosed with ASD exhibit more of the "higher order" RRBs which are typically seen in older individuals or those with higher intellectual ability (Militerni et al., [<reflink idref="bib21" id="ref79">21</reflink>]). One explanation for the disparity of clustering in ASD and ONDDs is that "Lower Order" RRBs are more typical of ASD than "Higher Order" RRBs and that there is a trait of ASD that is not currently captured which could help explain the disparity between the groups.</p> <p>The disparity in clustering of RRBs between the ASD and the ONDDs groups suggests the importance of further examination of RRBs within clinical populations, as clarifying the RRB profile may aid in better identifying children who have ASD at an earlier age, as well as distinguishing those with atypical presentations who do not have ASD. Although RRBs are seen in typical development (Evans et al., [<reflink idref="bib6" id="ref80">6</reflink>]; Thelen, [<reflink idref="bib32" id="ref81">32</reflink>]; Wolff et al., [<reflink idref="bib41" id="ref82">41</reflink>]), these results suggest that RRBs may clearly differentiate children with ASD from those with other developmental concerns at a young age. Furthermore, the results of the current study may point towards using RRBs to guide screening of children who are referred for an ASD evaluation to better identify children who are at higher risk of having ASD.</p> <p>A recently published exploratory factor analysis of the ADI-R (Hiruma et al., [<reflink idref="bib10" id="ref83">10</reflink>]) with 827 pre-school children (ages 35 to 71 months) with and without ASD found three factors in the ASD group: Repetitive Sensorimotor Behaviors, Insistence on Sameness, and Novel Stereotyped Speech. As previously discussed, it is likely that a large percentage of the children in our sample did not have sufficient verbal abilities to be considered for repetitive speech behaviors. Therefore, the additional factor of Novel Stereotyped Speech found in the recent publication was unlikely to be found in the current sample. The other differences in findings could be attributed to multiple factors: age, sociodemographics, sample size differences, and response-collapsing. The current study utilized a larger age range, did not have differences across race and gender, and had a smaller sample size difference between the ASD and ONDD groups, which could indicate that the current study is more representative of the expression of RRBs across multiple measures of diversity. Lastly, the recently published study did not have a diversity of responses on the ADI-R and had to collapse the severity of parent-reported behaviors into a dichotomous variable in the ONDD group. The current study did not need to collapse the severity ratings in the ONDD group, and therefore could represent a greater severity range of RRBs across neurodevelopmental disabilities.</p> <hd id="AN0191290297-15">Limitations</hd> <p>Several limitations should be noted for this study. Due to the nature of a clinical database and the grouping of the ONDDs, specific conclusions cannot be made about specific ONDDs (e.g. language disorder, global developmental delay, and ADHD) diagnoses and how their RRBs are expressed. Future studies should consider breaking down ONDD groups into the specific diagnosis received to determine whether there are differences in RRB profiles between these smaller groups. Additionally, the current sample reflects preschool and school-aged ONDDs and does not provide an explanation for how ONDDs may change throughout development (e.g. adolescence and adulthood). Future studies should consider longitudinal analyses of RRBs, as these profiles may change over time and be helpful in identifying children of all ages who are at risk for ASD based on the RRBs exhibited. Lastly, due to the lack of scale sensitivity, the ADI-R may not be a sensitive measure for understanding RRB factors and future studies should consider additional measures of RRBs, such as the Repetitive Behavior Scale Revised (RBS-R) (Lam & Aman, [<reflink idref="bib12" id="ref84">12</reflink>]) or the Behavior and Sensory Interests Questionnaire (Hanson et al., [<reflink idref="bib7" id="ref85">7</reflink>]) in order to validate the existence of these clusters. Lastly, future studies should consider the RRBs of children of varying ages, as well as language and cognitive abilities, as these variables may influence the RRBs exhibited (Harrop et al., [<reflink idref="bib9" id="ref86">9</reflink>]; Militerni et al., [<reflink idref="bib21" id="ref87">21</reflink>]; Ozonoff et al., [<reflink idref="bib23" id="ref88">23</reflink>]; Richler et al., [<reflink idref="bib25" id="ref89">25</reflink>]; Wolff et al., [<reflink idref="bib41" id="ref90">41</reflink>]).</p> <hd id="AN0191290297-16">Conclusions</hd> <p>The expression of RRBs across neurodevelopmental disabilities is well documented, but the differential expression of RRBs across ASD and ONDDs has not been fully explored. The current study was one of the first to explore this differential expression in a clinical sample of ASD and ONDDs via an exploratory factory analysis of the ADI-R. The results mirror previous literature, finding distinct RRB factors of Repetitive Sensorimotor and Insistence on Sameness. However, ONDDs had distinct RRB factors of Unusual Preoccupations, "Higher Order" (e.g., circumscribed interest, verbal rituals) and "Lower Order" (e.g., hand/finger mannerisms) behaviors, suggesting that the "Lower Order" RRBs might be more unique to ASD than other RRBs. Increasing the understanding of how RRBs present in clinical samples referred for ASD evaluation may aid in improved detection and diagnosis of children with ASD.</p> <hd id="AN0191290297-17">Author contributions</hd> <p>Helen Root, Monica Abdul-Chani, Sarah O'Kelley, and Kristi Guest contributed to the study conception and design. Material preparation, data collection and analysis were performed by Helen Root and Monica Abdul-Chani. The first draft of the manuscript was written by all authors and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.</p> <hd id="AN0191290297-18">Declarations</hd> <p></p> <hd id="AN0191290297-19">Competing Interests</hd> <p>There are no competing interests for the authors to report.</p> <hd id="AN0191290297-20">Publisher's Note</hd> <p>Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.</p> <ref id="AN0191290297-21"> <title> References </title> <blist> <bibl id="bib1" idref="ref2" type="bt">1</bibl> <bibtext> American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders (DSM-5®), Text Revision (5th ed.). American Psychiatric Pub.</bibtext> </blist> <blist> <bibl id="bib2" idref="ref38" type="bt">2</bibl> <bibtext> Bayley, N. (2006). Bayley Scales of Infant and Toddler Development, Third Edition. San Antonio, TX: Harcourt Assessment.</bibtext> </blist> <blist> <bibl id="bib3" idref="ref13" type="bt">3</bibl> <bibtext> Berry K, Russell K, Frost K. 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  Data: Structure of Restricted Repetitive Behaviors of Individuals Referred for Autism Spectrum Disorder Assessment
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  Data: <searchLink fieldCode="AR" term="%22Helen+Kay+Root%22">Helen Kay Root</searchLink><br /><searchLink fieldCode="AR" term="%22Monica+M%2E+Abdul-Chani%22">Monica M. Abdul-Chani</searchLink><br /><searchLink fieldCode="AR" term="%22Zachary+Enos+Arnold%22">Zachary Enos Arnold</searchLink><br /><searchLink fieldCode="AR" term="%22Jeremy+J%2E+Cottle%22">Jeremy J. Cottle</searchLink><br /><searchLink fieldCode="AR" term="%22Timothy+Hilty%22">Timothy Hilty</searchLink><br /><searchLink fieldCode="AR" term="%22Kristi+Carter+Guest%22">Kristi Carter Guest</searchLink><br /><searchLink fieldCode="AR" term="%22Sarah+E%2E+O'Kelley%22">Sarah E. O'Kelley</searchLink>
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  Data: <searchLink fieldCode="SO" term="%22Journal+of+Autism+and+Developmental+Disorders%22"><i>Journal of Autism and Developmental Disorders</i></searchLink>. 2026 56(1):100-109.
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  Data: Springer. Available from: Springer Nature. One New York Plaza, Suite 4600, New York, NY 10004. Tel: 800-777-4643; Tel: 212-460-1500; Fax: 212-460-1700; e-mail: customerservice@springernature.com; Web site: https://link.springer.com/
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  Data: <searchLink fieldCode="DE" term="%22Behavior+Problems%22">Behavior Problems</searchLink><br /><searchLink fieldCode="DE" term="%22Symptoms+%28Individual+Disorders%29%22">Symptoms (Individual Disorders)</searchLink><br /><searchLink fieldCode="DE" term="%22Autism+Spectrum+Disorders%22">Autism Spectrum Disorders</searchLink><br /><searchLink fieldCode="DE" term="%22Neurodevelopmental+Disorders%22">Neurodevelopmental Disorders</searchLink><br /><searchLink fieldCode="DE" term="%22Children%22">Children</searchLink><br /><searchLink fieldCode="DE" term="%22Child+Behavior%22">Child Behavior</searchLink><br /><searchLink fieldCode="DE" term="%22Screening+Tests%22">Screening Tests</searchLink>
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  Data: 10.1007/s10803-024-06536-7
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  Data: Purpose: Restricted and/or repetitive displays of behavior, interests, or activities (RRBs) are one of the core symptom domains of autism spectrum disorder (ASD). Current and past research indicates two 'clusters' of RRBs in children with ASD: repetitive sensorimotor (e.g., hand/finger and more complex motor mannerisms) and insistence on sameness (e.g., resistance to changes in the environment) behaviors. The current study aims to fill a gap by examining how RRBs may diverge in individuals with ASD and with other neurodevelopmental disorders (ONDD) in a clinical sample. Methods: A total of 558 individuals were seen at a tertiary care clinic for a comprehensive clinical assessment of ASD. The sample was split into ASD (n = 292 individuals) and ONDD (n = 266) groups based on clinical diagnosis. Exploratory factor analyses were conducted using Autism Diagnostic Interview-Revised (ADI-R) RRB item scores for the overall sample, the ASD group, and the ONDD group. Results: Exploratory factor analysis of ADI-R RRB items indicated a 2-factor solution for the full sample and ASD group. Items loaded onto two factors comprised of "Repetitive Sensorimotor" and "Insistence on Sameness" behaviors, consistent with previous literature. Results demonstrated a unique loading pattern for the non-ASD group, with items clustering into "Higher Order" (e.g., circumscribed interests) and "Lower Order" (e.g., hand and finger mannerisms) behaviors. Conclusion: The results of the current study may point towards using RRBs to guide screening of children who are referred for an ASD evaluation to better identify children who are at higher risk of having ASD.
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