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Intellectual Disability

Intellectual or cognitive functioning refers to an individual’s thinking or reasoning skills, which are expressed both verbally and nonverbally. Verbal reasoning skills include how one understands and uses language to describe what they know. Nonverbal or perceptual reasoning skills rely less heavily on verbal communication and include visual-spatial skills, being able to solve problems using visual and tactile methods, and quantitative reasoning ability. Intellectual or cognitive functioning also refers to an individual’s cognitive proficiency, which refers to abilities associated with completing tasks quickly, efficiently, and accurately. Cognitive proficiency can be thought of as the brain’s ‘horsepower’. It includes auditory and visual working memory skills, as well as processing speed, which refers to how quickly or accurately an individual is able to take in and use information from their environment.

An intellectual disability may be diagnosed when an individual’s intellectual and adaptive functioning is significantly below what would be expected compared to same-age peers. Adaptive functioning refers to a person’s ability to engage in and independently complete daily living skills at home, the school, and in the community at a level expected when compared to other people their age. These skills can be categorized into conceptual (e.g., communication skills, self-direction), social (e.g., social skills), and practical (e.g., self-care, ability to use community resources) areas.

If concerns have been identified in any or all of these areas, an assessment of the individual’s intellectual ability and adaptive skills may be important for determining his/her level of functioning. Such an assessment can be useful for understanding a person’s overall cognitive abilities, as well as their individual strengths and areas of challenge. This information can then be used to help with educational planning, placement, and acquiring appropriate services and supports.

To determine an individual’s level of cognitive and adaptive functioning, or experienced clinicians will:

  • Assess cognitive abilities through standardized intelligence testing (e.g., WISC-V).
  • Assess adaptive functioning through clinical interview, observation, and parent, teacher, and/or self rating scales/questionnaires.