Intellectual Disability

See the Assessment section of the Intellectual Disability evidence map for pertinent scientific evidence, expert opinion, and client/caregiver perspective.


SLPs screen for hearing, speech, language, communication, and swallowing problems. Screening does not result in a diagnosis of a disorder but, rather, determines the need for further assessment and/or referral for other services. Screening may not be a needed step for individuals with ID, particularly those with more severe limitations in intellectual or adaptive functioning. For these individuals, a comprehensive assessment is likely to be the first step.

Screening typically includes

  • gathering information from parents, teachers, and co-workers regarding concerns about an individuals language(s) and skills in each language;
  • conducting a hearing screening to rule out hearing loss as a possible contributing factor to language difficulties;
  • administering formal screening assessments that have normative data and/or cutoff scores and that have demonstrated evidence of adequate sensitivity and specificity;
  • using informal measures, such as those designed by the clinician and tailored to the population being screened (e.g., preschool, school-age/adolescence, adult);
  • observing speech production, language comprehension and production, social communication, and literacy skills in natural environments; and
  • conducting a screening of swallowing function.

Screening may result in recommendations for

  • complete audiologic assessment;
  • comprehensive language assessment;
  • comprehensive speech sound assessment, if the speech sound system is not appropriate for the individuals age and/or linguistic community;
  • comprehensive literacy assessment; and
  • referral for other assessments or services.

Comprehensive Assessment

Collaboration and Teaming

Assessment for individuals with ID involves multiple professionals due to the varying and far-reaching needs across developmental domains. Team models may be multidisciplinary, interdisciplinary, or transdisciplinary (see collaboration and teaming).

The particular collaborative team model that is selected depends on the needs of the individual with ID. Team members determine strengths and limitations in adaptive functioning and collaboratively determine the levels of supports needed across conceptual, social, and practical domains.

The role of SLPs and audiologists is to assess the individuals speech, language, and hearing skills. Assessments are sensitive to cultural and linguistic diversity and address components within the ICF (WHO, 2001) framework, including body structures/functions, activities/participation, and contextual factors. Findings from the communication and hearing assessments should be analyzed in the context of findings from other professionals (e.g., psychologist) for whom an ID diagnosis is within their purview.

Components of a Comprehensive Assessment

Both formal and informal assessment approaches can be used. Formal testing may be required if diagnosis or eligibility have yet to be determined for a child at risk for, or suspected of, a DD. Informal testing may be most useful to determine the childs achievement of specific developmental milestones. See assessment tools, techniques, and data sources that may be used in a comprehensive communication assessment. Dynamic assessment may be used to identify nonsymbolic and symbolic communication behaviors and to evaluate individual learning potential (Pea, 1996; Snell, 2002).

The comprehensive assessment may include the following, depending on the age and functioning of an individual with ID and his or her needs:

  • Case history, including medical, educational, and vocational status as well as teacher, caregiver, employer, and client/patient perspectives on the problem.
  • Interview with family members about communication during daily routines.
  • Review of auditory, visual, motor, and cognitive status, including hearing screening.
  • Assessment of
    • nonsymbolic (e.g., gestures, vocalizations, problem behaviors) and/or symbolic (e.g., words, signs, pictures) communication;
    • play;
    • social interaction and social communication;
    • spoken language (listening and speaking);
    • written language (reading and writing);
    • speech production;
    • oral motor skills;
    • swallowing; and
    • fluency.
  • Assessment for AAC and/or other assistive technology.
  • Identification of the potential for effective intervention strategies and compensations.

Details regarding the components of a comprehensive assessment are available on the following Practice Portal pages:

For individuals with ASD and ID, also see autism spectrum disorder and social communication disorders in school-age children for relevant assessment considerations based on individual needs.

Information provided in Communication Characteristics: Selected Populations With an Intellectual Disability may be useful in putting together an assessment protocol to document an individual performance profile. For example:

  • Children with Down syndrome often have a specific deficit in expressive syntax relative to semantics. They also have difficulty with speech production due to low muscle tone and characteristic facial dysmorphlogy (Berglund, Eriksson, & Johansson, 2001; Roberts, Price, & Malkin, 2007). Therefore, children with Down syndrome may require a detailed evaluation of syntactic production relative to comprehension along with a speech intelligibility inventory.
  • Individuals with Fragile X syndrome often have pragmatic language difficulties (Abbeduto & Sterling, 2011). They would benefit from a detailed evaluation of social communication relative to language structure and function.

Assessment may result in

  • diagnosis of a communication disorder or delay, secondary to ID;
  • description of the characteristics and severity of the communication disorder or delay;
  • determination of performance variability as a function of communicative situations/contexts;
  • identification of possible hearing problems;
  • recommendations for intervention and support;
  • recommendation of a communication system (e.g., low-tech or speech-generating device [SGD]);
  • referral to other professionals as needed (e.g., physician, physical therapist, occupational therapist, psychologist, or counselor);
  • recommendations for support for parents, caregivers, teachers, and employers; and
  • recommendations for support for transitions (e.g., early intervention into school age; school age into work place).

Family-Centered Practices

Persons with ID and their families are integral to the assessment process and are pivotal decision makers in determining specific goals and objectives and how clinical services should be provided following the assessment.

Families offer an important and unique knowledge base about the strengths, challenges, and needs for the individual with ID. They provide useful information about communication skills during daily routines. They also identify valued life outcomes for their children (e.g., being safe and healthy, having a home, establishing meaningful relationships, having choices and control, and creating opportunities for meaningful activities across environments; Giangreco, 1990). Ultimately, the decision about specific goals and objectives rests with the family and the person with ID, recognizing that the individual family circumstances and values are central to the decision-making process.

See family-centered practice for general guidelines.

Cultural and Linguistic Factors

Individuals with ID commonly experience stigmatization, discrimination, and health inequalities across cultures (Allison & Strydom, 2009). Because of this, some family members may not be willing to seek services, even when such services are readily available.

Linguistic factors may influence an assessment protocol when working with individuals who are multilingual. Careful consideration of language history (e.g., quality and duration of exposure to different languages) and linguistic abilities in all languages is necessary in the evaluation. See bilingual service deliverycultural competence, and collaborating with interpreters for additional information.

Eligibility for Services

Individuals with ID of all ages are eligible for SLP services because enhancement of communication skills is needed to function effectively, regardless of age or cognitive level relative to communication abilities. Eligibility is an area that has continued to evolve as the rights of individuals with ID have been increasingly well-recognized. In fact, the NJC emphasizes that there are no prerequisites for communication (NJC, 2002, 2003).

Beginning with the Developmental Disabilities Services and Facilities Act of 1970 (PL 91-517), eligibility rules for service delivery for ID have undergone widespread change (e.g., Hauber, 1984; Kohlenberg, Mack, & Brown, 1996; Whitney-Thomas, Timmons, Gilmore, & Thomas, 1999).

Categorically applying a priori criteria in making decisions on eligibility for services is not consistent with the law and IDEA regulations (IDEA, 2004). These a priori criteria cause concern when applied without regard to individual needs. They include discrepancies between cognitive and communication functioning (cognitive referencing); diagnosis; absence of prerequisite cognitive or other skills; and failure to benefit from previous communication services and supports. See NJC (2002, 2003) for information related to a priori criteria. Also see ASHAs resource page on cognitive referencing.

Cognitive referencing is a particular concern when applied to individuals with disabilities in general and to individuals with ID in particular (Casby, 1992; Cole, Dale, & Mills, 1990; Cole & Fey, 1996; Notari, Cole, & Mills, 1992). Cognitive referencing rests on the assumption that language skills cannot improve beyond cognitive ability. Relevant research indicates that language intervention benefits children with ID even when no language–cognition discrepancy exists (D. Carr & Felice, 2000; Cole et al., 1990; Warren, Gazdag, Bambara, & Jones, 1994).

The absence of prerequisite cognitive or other skills for determining eligibility is also of concern for individuals with ID. There are no prerequisites for communication supports and services, including the use of AAC (Romski & Sevcik, 2005). For example, some individuals with ID may be good candidates for immediate introduction of symbolic communication goals that target acquisition and use of words or AAC symbols. For individuals with extremely limited functional communication, other short-term goals may be equally appropriate (e.g., broader communication goals such as turn-taking and social participation, both of which involve nonsymbolic modes such as gesturing).

For information about eligibility for services in the schools, see eligibility and dismissal in schools, IDEA Part B Issue Brief: Individualized Education Programs and Eligibility for Services, and 2011 IDEA Part C Final Regulations.

Adolescents and Adults With ID

Individuals with ID continue to develop communication skills beyond the school years (e.g., Cheslock, Barton-Hulsey, Romski, & Sevcik, 2008). As the person with ID reaches adolescence and adulthood, his or her communication and functional needs change. For example, the teen years place a premium on peer interactions, use of social media, and communication skills needed to optimize acceptance and relationship development.

Individuals transitioning from school to vocational settings will need communication skills specific to the work setting (e.g., talking with co-workers and supervisors, interacting with customers).

SLPs work to maximize the participation and independence of individuals with ID as they experience life transitions that place new demands on communication. The speech-language assessment will need to incorporate an evaluation of skills needed to support the individuals changing communication needs.

ID and Hearing Loss

An increased prevalence of hearing loss has been reported in individuals with ID as compared with the general population. For example, considerable rates of conductive hearing loss have been reported in children with Down syndrome (e.g., Hess, Rosanowski, Eysholdt, & Shuster, 2006; Park, Wilson, Stevens, Harward, & Hohler, 2012), and Herer (2012) found that the prevalence of hearing loss in noninstitutionalized adults with ID was higher than for individuals in the general population and that the hearing loss occurred at a much younger age.

Therefore, early detection of hearing loss and routine monitoring are essential for ensuring positive communication outcomes. The comprehensive assessment includes a hearing screening and referral for a complete audiological assessment, if hearing concerns are indicated.

See permanent childhood hearing loss and hearing loss–beyond early childhood for more information.

Challenging Behaviors

Comprehensive assessment of individuals with ID involves assessment of the function of challenging behaviors, also known as problem behaviors. Common challenging behaviors include aggressive, disruptive, self-injurious, and stereotypic behaviors.

Challenging behaviors can function as a means to gain attention (social reinforcement), express wants or needs (tangible reinforcement), indicate frustration or a desire to avoid a nonpreferred activity or event (escape-avoidance), or gain sensory input (sensory reinforcement).

Understanding these broad functions of nonspeech modes can lead to greater understanding of the potential communication functions of challenging behaviors (e.g., Reichle & Wacker, 1993) and development of responsive interventions. This knowledge serves as the basis for replacing problem behaviors with more appropriate communication skills, including AAC, that would serve the same functions (see functional communication training [FCT] in the Treatment section).

Differential Diagnosis

SLPs need to differentiate between ID and other disorders and conditions (e.g., spoken language disorders and hearing loss) whose communication problems—particularly when severe—can be mistakenly attributed to ID (e.g., late language emergence and ASD).

Developmental Delay

Developmental delay (DD) is commonly used as a temporary diagnosis in young children at risk for ID. It indicates a failure to achieve age-appropriate developmental milestones (Petersen, Kube, & Palmer, 1998). More severe impairments are more likely to result in early identification of ID (Daily, Ardinger, & Holmes, 2000).

Often, the first sign of a developmental problem—including in milder forms of ID—is delayed language development. Therefore, SLPs may need to help make a differential diagnosis between (a) late language emergence and (b) ID or another DD.


SLPs may receive referrals for children with communication delays or deficits and limitations in social functioning. These behaviors may signal ASD, ID, or other conditions. The SLP may be part of a team making a differential diagnosis between ID and ASD or a diagnosis of comorbidity. Diagnosis of ID or ASD may be difficult because of the similarities and co-morbidity between the two conditions.

Commonalities between ASD and ID include:

  • onset during the developmental period;
  • deficits in nonspoken and verbal communication skills;
  • limitations in social participation; and
  • attention and academic difficulties.

Differences between ASD and ID include the following:

  • Individuals with ID have deficits in intellectual functioning, by definition; however, individuals with ASD have a range of intellectual abilities, from having an IQ within normal limits to having severe IQ limitations.
  • Individuals with ID usually develop skills slower than do their typically developing peers, but some follow patterns of typical development; those with ASD may not follow the typical developmental progression of skills across domains (e.g., communication and social interaction).
  • Research shows that individuals with ASD have difficulty with theory of mind (i.e., understanding the perspective of others), regardless of their level of cognitive functioning; these difficulties are more severe in individuals with ASD than in individuals with ID alone (Yirmiya, Erel, Shaked, & Solomonica-Levi, 1998).

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