Which feature best distinguishes Autism Spectrum Disorder (ASD) from Intellectual Disability (ID) in a 4-year-old child?

Explanation

## Distinguishing ASD from Intellectual Disability ### Core Difference **Key Point:** The hallmark discriminator between ASD and ID is the **qualitative nature of social-communication deficits and the presence of restricted, repetitive behaviors (RRBs)**. While ID affects global cognitive development uniformly, ASD is characterized by a specific profile of social-pragmatic dysfunction and stereotyped behaviors, even when IQ is normal or mildly reduced. ### Comparative Features | Feature | ASD | Intellectual Disability | |---------|-----|------------------------| | **Social reciprocity** | Qualitatively abnormal (lack of joint attention, poor eye contact, reduced social interest) | Delayed but developmentally appropriate for mental age | | **Restricted/repetitive behaviors** | Core diagnostic criterion; prominent and intrusive | Absent or minimal; not a defining feature | | **Communication pattern** | Pragmatic deficits, echolalia, atypical prosody; may have normal vocabulary | Delayed across all language domains; proportionate to overall delay | | **Adaptive functioning** | Uneven profile (may excel in certain areas while struggling socially) | Global impairment proportionate to IQ | | **Cognitive profile** | Uneven (peaks and valleys; may have savant skills) | Relatively uniform delay across domains | | **Onset** | Symptoms present from infancy; regression possible | Gradual global delay evident early | ### Clinical Pearl **Clinical Pearl:** A child with ASD may have normal or near-normal IQ but profound social-communication deficits and rigid behavioral patterns. Conversely, a child with ID shows proportionate delays across all areas without the qualitative social peculiarities or RRBs that define ASD. The two conditions can coexist (ASD + ID), but RRBs and social-pragmatic dysfunction are the true discriminators. ### High-Yield Distinction **High-Yield:** DSM-5 diagnostic criteria for ASD explicitly require: 1. Persistent deficits in social communication and interaction (across multiple contexts). 2. Restricted, repetitive patterns of behavior, interests, or activities. ID is defined solely by deficits in intellectual and adaptive functioning. The presence of criterion 2 (RRBs) in a child without global cognitive delay strongly suggests ASD over ID. ### Mnemonic **Mnemonic:** **RRBS = ASD's Red Flag** — Restricted, Repetitive Behaviors and interests are the Signature discriminator of ASD. ID lacks this qualitative behavioral signature.