Contact Us

Want to learn more about Riverside?      Contact Your Local Assessment Consultant

Clinical and Special Education Woodcock-Johnson

Assessment Plan: A Guide for Evaluating Intellectual Disabilities

Dr. Geremy Grant
Written By Dr. Geremy Grant
On Jan 12, 2022
4 minute read

Assessment Planning for Intellectual Disabilities

Intellectual Disability (ID) is recognized in the field of education by Federal mandates (e.g., under the IDEA), and in the field of clinical practice (e.g., DSM-5, ICD-10-CM). ID affects roughly 1% of the population, with a higher prevalence generally seen in males when compared to females. The onset of ID typically begins in childhood and follows a life-long course. This course may be improved with early and continuing intervention.

Intellectual Functioning

Determination of ID requires standardized assessment gauging an individual’s intelligence. Intellectual assessment should involve measures tapping skills critical to day-to-day functioning such as, reasoning, problem solving, planning, judgment, and abstract thinking. Utilization of the WJ IV Tests of Cognitive Abilities (WJ IV COG) affords examiners with flexible testing options when assessing for ID. The WJ IV COG offers multiple cognitive composites providing an overall view of an individual’s functioning (General Intellectual Ability, Brief Intellectual Ability, and the Gf-Gc composite).

General Intellectual Ability (GIA)

The GIA is based on Tests 1-7 of the Cognitive Battery, which are “weighted ” to provide the best overall estimate of an individual’s intellectual functioning. The Tests “weights” imply how much they contribute to the GIA. For example, Fluid Reasoning contributes more to the GIA when compared to Working Memory. However, all seven ability domains that make up the GIA score play some role in its calculation. As such, it is possible that the true level of an individual’s impairment may be masked depending on their performance on simpler/rote tasks (e.g., those falling within the processing speed domain).

Brief Intellectual Ability (BIA)

The BIA is based on Tests 1-3 and is best used as a screener or for re-evaluation purposes. Unlike the GIA, the Tests have equal “weights”, meaning that they each equally contribute to the overall BIA score. Given this composite only assesses three of the seven CHC factors it may not provide the depth of information needed when assessing for ID.

Gf-Gc Composite (Fluid Reasoning and Comprehension-Knowledge)

This composite is structured to include the two highest-order factors (fluid reasoning and comprehension-knowledge) related to the concept of intelligence. This composite reviews a person’s reasoning abilities and knowledge, two crucial pieces for consideration in ID assessment. It offers a comparison point to the GIA that can be used to determine if the GIA may be inflated due to performance within lower-order areas of cognitive functioning. This composite may be particularly useful in identifying more mild cases of ID, where individuals may be able to meet the demands of these lower-order tasks.

Although specific IQ scores are not required for diagnosing/classifying an individual as ID, the consensus remains that the cognitive composite score should fall at or below two standard deviations of the population mean.

Adaptive Functioning

Determination of ID also requires an individual to present with deficits in adaptive functioning. Adaptive functioning relates to how well an individual can meet their day-to-day responsibilities through the use of life skills. Emphasis is placed on adaptive functioning to determine an individual’s severity level (e.g., mild, moderate, severe, profound).

A comprehensive assessment of Adaptive Functioning is best to gauge specific areas would benefit from intervention. The Adaptive Behavioral Assessment System, Third Edition (ABAS-3) is a tool that can be useful in ID assessment. The ABAS-III can be used for those between the ages of birth to 89 years. It investigates functioning in 11 various skill areas necessary for success in life, which fall within three major adaptive domains (conceptual, social, and practical). These domains and skill areas are listed below:

Intellectual Abilites Blog Image


Like the WJ IV COG, the ABAS-3 allows for an analysis of an individual’s strengths and weaknesses. Results can be synthesized into an Interpretive Report to expedite planning and implementation of supports. The ABAS-3 is coupled with an unlimited-use scoring assistant and intervention planner software.


  •  The IQ score is not the sole determinant of ID classification.
    • Not all cognitive composites are built the same.
    • The Gf-Gc is ideal to isolate the higher-order functions related to the concept of intelligence, while controlling for the influence of lower-order tests.
  •  Comprehensive adaptive assessment is vital to determining ID severity levels.
    • This should include a review of life skills needed for independence and meeting social responsibilities. An assessment which allows for a review of patterns of strengths and weaknesses, in addition to comparisons to reference groups is best.

To learn more about other considerations for identifying ID, read the article below!

Navigating the Challenges of Identifying SLD and ID

Recommended Articles:

Submit a Comment

Subscribe to our newsletter

Click here to subscribe

Stay up to date