Repetitive and Restricted Behaviors and Interests in Autism Spectrum Disorders

Executive Summary

This comprehensive examination of restricted and repetitive behaviors and interests (RRBIs) challenges deficit-based assumptions by demonstrating that these behaviors often serve critical adaptive functions—sensory regulation, anxiety management, attention maintenance, and emotional grounding. Rather than representing pathology requiring elimination, RRBIs exist on a continuum from adaptive assets to participation barriers, requiring individualized functional analysis rather than suppression. The research reveals two neurobiologically distinct domains—Repetitive Sensory Motor Behaviors (linked to motor development and basal ganglia function) and Insistence on Sameness (linked to frontostriatal circuits and anxiety regulation)—which develop independently and require different intervention approaches. Critical findings include the bidirectional relationship between anxiety and insistence on sameness mediated by intolerance of uncertainty, significant gender differences in RRBI expression that contribute to underdiagnosis in females, and the importance of leveraging special interests as motivational assets rather than treating them as deficits. The evidence consistently shows that reducing interfering behaviors without simultaneously building adaptive alternatives produces insufficient or counterproductive outcomes, while neurodiversity-affirming approaches that distinguish between helpful and hindering behaviors based on individual function rather than social appearance produce more sustainable improvements in daily participation and well-being.

Overview and Core Concepts

Definition and Classification of RRBIs

RRBIs constitute a core diagnostic feature of Autism Spectrum Disorder characterized by repetition, rigidity, invariance, and situational inappropriateness. The DSM-5 identifies four symptom categories: stereotyped speech, movement, or object use; extreme resistance to change and rigid adherence to routines; circumscribed and intense interests; and unusual sensory responses. Only two of four types are required for diagnosis, reflecting the heterogeneity of autistic experiences. Importantly, RRBIs manifest across all autistic individuals regardless of age or cognitive level, though expression varies considerably.

Research identifies two distinct overarching domains with separate developmental trajectories and underlying mechanisms. Repetitive Sensory Motor Behaviors include stereotyped motor behaviors, body rocking, spinning, repetitive object manipulation, and atypical sensory responses. These lower-order behaviors correlate with motor system development and basal ganglia function. In typical development, they peak at 12–15 months when approximately 60% of infants show repetitive hand movements like toy fiddling, then decline sharply by ages 2–3 years as motor control matures. In autistic individuals, RSMB remain elevated and persistent, suggesting differential motor system maturation.

Insistence on Sameness encompasses behavioral rigidity, resistance to change, rituals, and circumscribed interests. These higher-order behaviors emerge rarely at age 2, increase gradually through early childhood, and remain relatively stable thereafter. In typical development, IS peaks between 24–48 months when children display strong preferences for sameness, rituals, and inflexible likes or dislikes, then declines by 48–72 months as self-regulation develops. In autistic individuals, IS remains elevated and persistent, potentially serving as a maladaptive self-regulation mechanism linked to frontostriatal circuits including the orbitofrontal cortex, anterior cingulate cortex, and their striatal connections.

Critically, RSMB and IS develop independently. Higher nonverbal IQ at age 2 predicts milder RSMB that reduce over time, but shows no effect on IS trajectory. This neurobiological distinction carries profound clinical implications: interventions effective for one domain may not work for the other, and assessment must clearly identify which domain(s) require targeting.

Subjective Meanings and Adaptive Functions

First-hand accounts from autistic individuals reveal that RRBIs serve multiple critical functions that external observers often misunderstand:

Arousal and Attention Regulation: Repetitive behaviors like object rubbing, pacing, and body rocking help maintain attention and concentration during learning, work, or social situations. One participant described hand movements during class as “accessibility”—necessary for concentration, not distraction. Research confirms that sensory motor behaviors facilitate rather than impede learning when they serve this regulatory function. The profound insight here is that behaviors appearing disruptive to observers often function as essential cognitive tools for autistic individuals.

Sensory Regulation: RRBIs function bidirectionally—blocking or diminishing overwhelming sensory input for hyper-responsive individuals, or seeking strong stimuli for under-responsive individuals. One participant described reading multi-sensory engagement as essential: “I think through my hands and legs…the physical presence is very important to me. Without the physical sensations I’ll sometimes ask myself if I even really exist.” This reveals sensory regulation’s existential significance—some autistic individuals experience repetitive sensory-motor behaviors as grounding mechanisms that maintain their sense of self and reality.

Emotional Regulation: Repetitive movements relieve stress, anxiety, and excitement, appearing most frequently during emotional extremes—severe distress or overwhelming joy. Self-injurious behaviors sometimes substitute unbearable emotional pain with more tolerable physical pain, or serve as arousal regulation upon waking. These behaviors, while concerning to observe, may represent the individual’s best available coping mechanism for managing intense emotional states.

Security and Coping with Uncertainty: Familiar routines, repetitive activities, and attachment to objects provide certainty and control. Participants described extreme anxiety when facing unexpected changes, with one noting: “I am always afraid that if change will come it won’t be me anymore.” This captures how insistence on sameness functions as anxiety management and identity preservation rather than mere behavioral inflexibility. The existential dimension here reveals that for some autistic individuals, predictability isn’t just preferable—it’s central to maintaining their sense of self and continuity.

Social Communication: Special interests build confidence in social interactions, provide meaningful conversation topics, and help make sense of complex social situations and emotions. Many autistic individuals report their interests facilitated academic success, employment, and social connection. Rather than representing social disengagement, circumscribed interests can serve as bridges to social participation and relationship-building.

Two Distinct Neurobiological Pathways

Understanding that RSMB and IS reflect distinct neurobiological systems helps explain why some interventions fail and why individuals require highly individualized approaches.

RSMB Neurobiological Pathway: Linked to motor system maturation and basal ganglia/motor cortex dysfunction. The basal ganglia (striatum, caudate, putamen, globus pallidus) control motor movements and generate context-dependent behaviors. Research found enlarged caudate nucleus volume correlates with compulsive behavior and motor stereotypies, larger right caudate volume correlates with higher repetitive behavior scores, and bilateral putamen enlargement appears in autism. Cortico-striatal connectivity studies identified imbalanced intrinsic functional connectivity in autism—increased for limbic circuits but reduced for frontoparietal and motor circuits—associated with RRBI severity. Motor cortex, supplementary motor area, and cerebellar gray matter volume differences correlate with RSMB severity, and these patterns differ by sex/gender (motor cortex and cerebellar patterns in girls; right putamen patterns in boys).

IS Neurobiological Pathway: The orbitofrontal cortex, anterior cingulate cortex, and their connections to striatal and limbic regions regulate behavioral rigidity and anxiety. In typical development, these circuits mature between ages 2–4 years, enabling more sophisticated self-regulation and anxiety reduction. In autism, documented delays in self-regulation abilities across multiple domains combine with elevated anxiety (40–87% prevalence in autism versus general population baseline) to perpetuate IS as the primary coping mechanism. Research found bidirectional relationships: effortful control mediates the IS-anxiety association while IS mediates relationships between effortful control and anxiety, suggesting IS persists due to inflexibility rather than actual functional benefit—it reduces anxiety acutely but prevents exposure to situations necessary for developing more adaptive coping strategies.

Neurotransmitter Systems and Genetic Foundations

Neurotransmitter Dysregulation

Dopamine: Plays a central role in RRBI generation. Dopamine agonists induce stereotypic behaviors in mammals; dopamine synthesis inhibition reduces RRBIs while dopamine precursors increase them; mutations in dopamine signaling pathways correlate with ASD diagnosis and “insistence on sameness” specifically. However, clinical evidence conflicts—some individuals with intellectual disability and RRBIs showed low homovanillic acid (dopamine metabolite), contradicting animal findings. This neurochemical heterogeneity reflects the genetic diversity underlying autism.

GABA: Involves inhibitory pathway changes; children with complex motor stereotypies showed lower GABA levels in anterior cingulate cortex and striatum, with reduced GABA levels correlating to greater motor stereotypy severity. GABA receptor agonists improved RRBIs in mouse autism models, suggesting potential intervention targets though clinical application remains underdeveloped.

Serotonin: Axon projections from raphe nuclei to basal ganglia create dopamine-5-HT interactions. Some individuals with ASD show higher blood serotonin levels; acute tryptophan depletion worsened stereotyped behavior. However, systematic reviews find insufficient evidence that SSRIs effectively treat autism in children or adults despite sometimes being prescribed, indicating serotonin-based interventions have limited specificity.

Glutamate: Excitatory signaling abnormalities may impair learning and memory, with genetic abnormalities in glutamatergic components correlating with ASD diagnosis. Glutamate dysregulation may interact with dopamine dysfunction in RRBI generation.

Genetic Basis and Syndrome-Specific Profiles

Approximately 1,000 genes potentially implicate in autism with no single common mutation, reflecting genetic heterogeneity. Seven specific RRBIs showed significant heritability: circumscribed interests, repetitive use of objects, compulsions/rituals, unusual sensory interests, general sensitivity to noise, unusual attachments to objects, and stereotyped body movements. Genome-Wide Association Studies identified novel risk genes including SLC35B1 and PHB. Parental heritability studies found children whose both parents scored in the top 20% for RRBI severity showed increased RRBI scores themselves.

Critically, genetic syndromes produce syndrome-specific RRBI profiles—Fragile X shows hand stereotypies and echolalia; Prader-Willi features hoarding and routine preference; Smith-Magenis syndrome shows people attachment. This indicates that specific genetic abnormalities produce characteristic behavioral patterns requiring targeted approaches rather than generic RRBI interventions.

Sensory Processing and RRBIs

Complex Bidirectional Relationships

Sensory features co-exist across hyper-, hypo-, and seeking patterns within individuals, and most autistic individuals show mixed sensory reactivity patterns rather than a single profile. Sensory modulation—the central nervous system’s ability to regulate responses to sensory input—determines RRBI expression. Dunn’s four-quadrant model classifies sensory difficulties based on neurological threshold (high/low stimulation needed for response) and behavioral style (passive/active): Poor Registration (attenuated responses to stimuli), Sensory Seeking (behaviors increasing stimulation due to inadequate registration), Sensory Sensitivity (withdrawal, anxiety, or internalizing symptoms), and Sensory Avoiding (active removal from overwhelming intense stimuli).

Two Competing Theories Explain Sensory-RRBI Links: The “over-arousal” theory posits that repetitive behaviors block sensory input perceived as threatening or too intense by sensory hyper-reactive individuals. Evidence supporting this includes increased sensory hyper-reactivity associating with increased frequency/intensity of all repetitive behavior types across ASD and typically developing groups regardless of gender, age, or IQ. The “seeking” theory proposes that repetitive behaviors provide additional sensory input for hypo-reactive individuals less able to use environmental sensory stimuli, facilitating self-regulation and learning. Evidence supporting this includes sensory hypo-reactivity significantly associating with increased repetitive motor behaviors, with hypo-reactivity being the strongest correlate of stereotyped movements.

However, both theories incompletely explain the complexity. Contradictory findings exist: hypo-reactivity associates with insistence on sameness, which is typically considered a control/reduction strategy linked to hyper-reactivity. Emerging research identifies intolerance of uncertainty and anxiety as partial mediators of sensory-RRBI relationships. One study found intolerance of uncertainty explained 50% of sensory sensitivity variance, partially mediated by anxiety. Sensory avoiding mediated relationships between insistence on sameness and anxiety.

Current estimates indicate 60–95% of individuals with ASD experience clinically significant sensory features, though this wide range reflects measurement variability. Families report significant functional restrictions due to sensory symptoms. Hyper-reactivity to specific sounds, food tastes/textures triggers avoidance behaviors and strong emotional reactions to routine changes; hypo-reactivity results in failure to notice salient stimuli or dangerous situations; distracting sensory experiences cause attention loss and social difficulties. Some individuals report enhanced sensory abilities (heightened visual detail awareness) supporting certain learning tasks.

Sensory Subtypes and Individual Profiles

Seven sensory subtype models have been proposed identifying distinct clusters varying by age and developmental level:

Lane Model (children aged 2–10 years, n=312): Four subtypes using Short Sensory Profile—(1) Sensory Adaptive (37.5%) with no clinically significant sensory difficulties; (2) Taste/Smell Sensitive (40.2%) with sensory reactivity difficulties and normal multisensory integration; (3) Postural Inattentive (10.3%) with multisensory integration impairments and normal sensory reactivity; (4) Generalised Sensory Difference (12.1%) with difficulties in both domains. Taste/Smell Sensitive showed highest communication difficulty and picky eating; those with greatest sensory reactivity difficulties exhibited highest challenging behaviors.

Ausderau Model (children aged 2–12 years, n=1,294): Four subtypes—(1) Mild (29%) with very few sensory symptoms; (2) Extreme-Mixed (17%) with high symptom levels across all domains; (3) Sensitive-Distressed (28%) with hyper-reactivity and enhanced sensory perception; (4) Attenuated-Preoccupied (17%) with hypo-reactivity and sensory seeking. Subtype membership stable at one-year follow-up (91%). ASD symptom severity greatest in Extreme-Mixed; Attenuated-Preoccupied showed lowest adaptive behavior and youngest age; Extreme-Mixed associated with highest parenting stress.

Adolescent Model: Shows different pattern with variation limited to severity of symptoms only, with no specific differences in sensory modality or specific sensory behaviors. Anxiety increased significantly with greater sensory symptoms.

Notably, many children with autism have mild or no clinically significant sensory symptoms, supporting the diagnostic approach where sensory features are “sufficient but not necessary” for ASD diagnosis. This challenges assumptions that sensory regulation is universally central to autism intervention planning.

Sex/Gender Differences and Diagnostic Implications

The male-to-female autism diagnosis ratio remains consistently reported at 4:1, ranging from 2.3:1 to 9:1 depending on cognitive ability. However, this disparity is not fully explained by biological factors alone.

Diagnostic Ascertainment Bias: Females receive autism diagnoses at older ages than males, particularly those with average or above-average IQ. Young girls tend to display fewer repetitive and restrictive behaviors than boys and may be referred for evaluation later. Historical research shows girls previously evaluated before age six for developmental concerns were not identified as having autism until age ten. Genetic research reveals females diagnosed with autism carry more genetic mutations associated with ASD than males with equivalent symptom levels, suggesting females require higher genetic or environmental loading to develop autism yet are diagnosed less frequently.

Quantitative RRBI Differences: Research consistently finds females exhibit fewer RRBIs overall compared to males, particularly in stereotyped motor behaviors, repetitive object use, and circumscribed interests. However, females demonstrate higher levels of self-injurious behavior, compulsive behaviors, and insistence on sameness. Girls’ interests often resemble those of typically developing girls (animals, horses, classical literature) but differ in intensity, quality, and time investment—not the topic itself.

Developmental Trajectory Differences: No sex/gender differences appear in early toddlerhood; significant differences emerge after age 6 years and continue through school-age and early adolescence, then reduce again in later adolescence and adulthood. This suggests camouflaging or suppression of behaviors rather than genuine developmental divergence.

Measurement Bias: ADOS-2 items most sensitive for identifying autism differ by age/functioning level—for younger/lower-functioning children, “unusual repetitive interests” and “unusual sensory interests” are most indicative (areas where girls score lower); for adolescents, “stereotyped/idiosyncratic speech” is more sensitive (again, an area where females are less impaired). Critically, the Social Responsiveness Scale-2 shows opposite patterns: females self-report higher RRBI than males on self-report measures, while parent/clinician observations show females as less impaired. This discrepancy highlights observational assessment systematically misses female presentations.

Anxiety, Intolerance of Uncertainty, and RRBIs

Anxiety is highly prevalent in autism (40–87% of individuals meet criteria for at least one anxiety disorder versus general population baseline), and complex bidirectional relationships exist with RRBIs.

RRBI Subtypes Show Different Anxiety Relationships: Insistence on Sameness consistently associates with higher anxiety levels across studies. Among anxious individuals with ASD, IS correlates with separation anxiety and peer physical injury but not other anxiety types. Sensory hyper-reactivity consistently associates with anxiety across age groups. For non-anxious individuals with ASD, repetitive movements correlate with OCD symptoms but not other anxiety types.

Three Mechanistic Models:

Model 1: Anxiety Causes RRBI — Anxiety motivates emergence of RRBIs through multiple pathways. RRBIs, particularly circumscribed interests and symbolic reenactment, serve as maladaptive coping mechanisms reducing anxiety by controlling the environment and creating predictable outcomes. This creates a problematic cycle: RRBI provides immediate anxiety relief, building positive beliefs about these behaviors, leading to increased reliance and further limiting engagement, perpetuating anxiety. Anxiety triggers sensory hyper-reactivity through hypervigilance—scanning for threat-related stimuli with attentional biases that make disengaging difficult.

Model 2: RRBI Causes Anxiety — Anxiety may result from RRBI consequences. Pervasive ASD-related challenges—cognitive, sensory, and social-communication deficits—can lead to RRBI like resistance to change and insistence on sameness, ultimately producing anxiety. ASD-specific stressors including unpredictability of social encounters, peer rejection/victimization, aversive sensory experiences, and inability to engage in preferred repetitive behaviors trigger anxiety and mood dysregulation. Sensory hyper-reactivity may trigger specific phobia or generalized anxiety through conditioning: aversive sensory stimuli become associated with specific objects/situations, conditioning these as fear-eliciting stimuli.

Model 3: Shared Mechanisms — Rather than one construct causing the other, intolerance of uncertainty mediates relationships between both. IU involves difficulty enduring uncertain situations and perceiving uncertainty as stressful and threatening. Two key IU factors resonate with ASD: desire for predictability and uncertainty paralysis. IS has been hypothesized as a strategy to reduce IU-related distress. IU mediates associations between broad autism symptoms and anxiety in children/adolescents and adults with ASD, and partially mediates associations between sensory sensitivity and anxiety.

RRBIs That Promote Vs. Inhibit Daily Life Participation

Promoting Participation: Structured routines reduce stress by providing predictability and clear organizational frameworks. Special interests demonstrate the most positive implications—they motivate academic engagement (students pursuing degrees in history, art, science, communication), support employment (individuals working in museums related to art interests, legal investigation), and enhance self-esteem through expertise. Knowledge accumulated through special interests manifests in productive leisure activities. Participants rejected the term “excessive engagement,” preferring “extended engagement” or “intensified engagement” to reflect the positive nature of deep focus comparable to figures like Albert Einstein.

Inhibiting Participation: Negative social responses create a problematic cycle—individuals hide adaptive repetitive behaviors due to social judgment, leading to avoidance of public settings and further social isolation. One participant described being asked to stop manipulating objects during class despite improved concentration. Sensory overload from repetitive behaviors (lasting hours to days) causes confusion, distraction, and avoidance of daily activities like grocery shopping or driving. Tactile sensitivities complicate self-care (avoiding hair combing, avoiding towel-drying face). The disconnect between adaptive RRBI functions and negative environmental reactions creates significant barriers to participation.

Related Conditions and Comorbidities

Eating Disorders and Selective Eating: Food selectivity affects approximately 90% of young children with ASD compared to 25–30% of typically developing children, manifesting as insistence on specific foods, preparation methods, and mealtime routines. Food restriction creates nutritional risks including under-nutrition, suboptimal growth, vitamin/mineral/amino acid deficiencies, and obesity for those with binge eating. Adolescents with eating disorders show histories of more repetitive, self-injurious, and compulsive behaviors plus insistence on sameness than non-eating-disordered peers.

Self-Injurious Behaviors: Though not included in DSM-5 ASD criteria, approximately half of interviewed individuals report self-injurious behaviors (scratching, head-banging, self-induced vomiting). These occur in response to severe emotional distress (attempting to convert unbearable emotional pain to more tolerable physical pain) or as arousal regulation (scratching deeply upon waking to transition from sleep). These behaviors warrant attention as indicators of severe mental distress requiring clinical intervention.

Practical Strategies and Intervention Approaches

Functional Behavioral Assessment and Analysis

Before intervening to reduce or change RRBIs, conduct thorough functional behavioral analysis identifying underlying mechanisms. Assessment involves: identifying various RRBIs performed; identifying which concern individuals/parents/caregivers/therapists; identifying behavior characteristics (frequency, duration, intensity, triggering contexts); identifying underlying mechanisms (sensory hyper/hypo-responsivity, communication needs, anxiety-related, attention-seeking, arousal regulation); evaluating fit between target behavior, environment (social/physical), and occupation (demands, roles, goals).

Different mechanisms require different intervention strategies: sensory-seeking behaviors benefit from environmental enrichment and matched alternatives; anxiety-driven behaviors require anxiety management and exposure therapy strategies; communication-based behaviors benefit from functional communication training; attention-seeking behaviors respond to attention-based reinforcement strategies.

Rep-Mod Intervention Model

The “Rep-Mod” model, based on ICF (International Classification of Functioning, Disability, and Health) and PEO (Person-Environment-Occupation) frameworks, proposes that disability results from environmental demands/opportunities interaction with person characteristics. Assessment involves identifying which RRBIs concern key stakeholders, identifying underlying mechanisms, and evaluating person-environment-occupation fit.

Intervention strategies integrate sensory-based and behavioral-based methods: Empowerment strategies integrate behaviors within adaptive activities (transform narrow interests into wider/functional interests or competitive work); Reduction methods reduce interfering behaviors while adding adaptive alternatives; Reassessment evaluates intervention effects on daily task participation, determining whether to cease/continue/modify intervention.

Antecedent-Based and Environmental Strategies

Environmental enrichment with competing reinforcers modifies conditions before behavior occurs. Remove positive reinforcers of non-adaptive behavior; provide matched alternatives (adaptive objects replacing problematic RRBIs); prompt engagement with alternatives; expand behavior/play repertoire; teach functional communication; use visual cues/schedules/video-guided technologies; incorporate physical exercise (jogging, horseback riding, martial arts, swimming, yoga/dance showed significant RRBI decreases in 5 of 6 studies, though effects may not maintain post-intervention).

Consequence-Based Strategies

Response interruption/redirection physically or verbally interrupts and redirects behavior. Extinction removes or terminates reinforcer. Differential reinforcement builds on restricted play by expanding repetitive behavior into more symbolic/social elements. Established evidence-based practices include: functional behavioral analysis, stimulus control/environmental modification, response interruption/redirection, functional communication training, extinction, and differential reinforcement.

Critical finding: Reducing RRBI alone is insufficient without purposefully strengthening alternative adaptive behaviors. Research found reducing RRBI associated with increases in other behaviors—sometimes adaptive but sometimes replacement with alternative non-adaptive behaviors. Therefore, intervention must simultaneously build competing adaptive skills.

Sensory-Based Interventions

Sensory Integration Therapy (clinic-based combinations of sensory/kinetic stimuli in child-directed activities) shows moderate evidence. Sensory-based interventions (classroom-based single-sensory strategies like balls/vests/swings to influence arousal) show promising evidence for goal attainment and reduced negative responses, though mixed results appear overall. Environmental enrichment (exposure to aversive stimuli for tolerance promotion) shows efficacy for improved sensory reactivity, ASD symptomatology, receptive language, non-verbal IQ. Auditory integration (filtered sound) shows some evidence of improved hearing sensitivity. Massage-based interventions show promising evidence for improved ASD symptom severity and sensory difficulties.

Important limitation: Heterogeneity in study design/populations, restricted quality, high bias risk, limited follow-up, lack of treatment fidelity, and unclear mechanisms limit the evidence base for sensory interventions.

Parent-Mediated and Family-Implemented Interventions

FITBI (Family-Implemented Treatment for Behavioral Inflexibility): Therapist and parent co-implementation over 12 weeks showed significant RRBI decreases at post-intervention, maintained for most participants. Lin & Koegel study (3 young children, self-management + PRT principles targeting higher-order RRBI): Gains in observed/parent-reported flexibility, increased activity variety, increased positive parent-child affect, reduced parent ratings on Repetitive Behavior Questionnaire. “Managing Repetitive Behaviours” program: 8-week group intervention for parents, developed in consultation with parents, incorporates video feedback/interactive activities/peer support emphasis. Pilot RCT (25 families) showed promising feasibility/acceptability/initial outcomes.

Working With Special Interests Rather Than Against Them

Rather than restricting or eliminating special interests, research supports leveraging them as motivational assets. Special interests can motivate academic and vocational engagement, build self-esteem through expertise development, support social communication, enhance subjective well-being and life satisfaction, and facilitate employment success when matched appropriately. Transform narrow interests into functional occupations; use special interests as reinforcement for learning other skills; expand interests through related educational pathways. For example, a child’s intense interest in specific animals can expand into biology, veterinary science, or animal care employment rather than being suppressed as “excessive.”