The public often associates autism with an individual who possesses a single, all-consuming “special interest,” such as trains, dinosaurs, or a niche academic subject. This intense focus is a recognizable trait in media portrayals and public perception of Autism Spectrum Disorder (ASD). If an autistic person lacks this fixated interest, it can cause confusion about the validity of their diagnosis. However, official diagnostic criteria show that this single trait, while common, is not mandatory for an autism diagnosis.
The Two Core Diagnostic Domains
To receive an Autism Spectrum Disorder diagnosis, an individual must meet criteria across two distinct categories defined in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Domain A focuses on persistent differences in social communication and social interaction. This domain requires deficits in social-emotional reciprocity, nonverbal communicative behaviors, and in developing, maintaining, and understanding relationships. All three areas must show persistent deficits. Domain B covers restricted, repetitive patterns of behavior, interests, or activities. A diagnosis requires meeting criteria in both Domain A and Domain B.
Identifying Restricted and Repetitive Behaviors
The Domain B criteria, which address Restricted and Repetitive Patterns of Behavior, Interests, or Activities (RRPB), is comprised of four distinct sub-criteria. For an individual to meet the RRPB requirement for an ASD diagnosis, they must demonstrate at least two of these four different sub-criteria. This structure is what makes the presence of a special interest non-mandatory for a diagnosis. The special interest that the public commonly associates with autism falls under only one of these four sub-criteria: Highly restricted, fixated interests that are abnormal in intensity or focus. The other three sub-criteria offer alternative ways to satisfy the RRPB domain:
- Stereotyped or repetitive motor movements, use of objects, or speech, such as hand flapping or repeating phrases (echolalia).
- Insistence on sameness, an inflexible adherence to specific, non-functional routines, or ritualized patterns of verbal or nonverbal behavior. This can manifest as extreme distress at small changes or a rigid need to follow a particular route or sequence of actions.
- Hyper- or hypo-reactivity to sensory input or an unusual interest in sensory aspects of the environment. This includes not reacting to pain or temperature, an adverse response to specific sounds or textures, or a visual fascination with lights or movement.
The Variability of Autistic Interests
While the intense special interest is a well-known characteristic, the manifestation of interests varies widely among autistic individuals. Studies suggest that a significant majority, potentially 75% to 90% of autistic people, do develop one or more special interests, but this still leaves a portion who do not. For many, the interest may not align with the common stereotypes of trains or mathematics.
An interest can be considered a “restricted interest” if it is pursued with unusual intensity and depth, even if the subject matter itself is common, such as an intense focus on a specific sports team or a particular genre of literature. The autistic person’s focus on collecting exhaustive details and dedicating an extensive amount of time makes them restricted in intensity. Furthermore, some individuals experience serial interests, where they move from one intense focus to another over time, rather than maintaining a single, lifelong passion. The intensity of the focus, rather than the topic’s unusual nature, is the defining factor in the diagnostic criteria. For some, the interest may be internal or abstract, such as an intense preoccupation with philosophical concepts or complex systems, which is not outwardly visible to others.
Diagnosis When Intense Focus is Absent
An individual can absolutely be autistic without possessing a special interest, provided they meet the remaining diagnostic requirements. The core of the diagnosis lies in meeting all criteria in the social communication domain (Domain A) and at least two of the four criteria in the restricted and repetitive behavior domain (Domain B). Since the special interest is only one of the four options in Domain B, an individual can easily meet the threshold by presenting with other characteristics.
For example, a person could be diagnosed with ASD if they exhibit significant differences in social communication (Domain A) combined with a strong insistence on sameness (RRPB Criterion 2) and significant sensory processing differences (RRPB Criterion 4). Meeting just these two criteria from the RRPB domain is sufficient, even without the presence of a highly restricted, fixated interest. The combination of characteristics is what matters for the diagnosis, not the presence of any single, specific trait. The diagnostic process is designed to look at the overall pattern of persistent differences across both core domains. The emphasis is on how the combination of these characteristics causes clinically significant impairment in daily functioning, rather than requiring the presence of any one specific trait like the special interest.