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-TR, 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 V Tests of Cognitive Abilities (WJ V COG) affords examiners with flexible testing options when assessing for ID. The WJ V 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 8 tests from the Cognitive Battery that are equally weighted across all ages. The GIA will often be the best single-score predictor of various global criteria such as overall school achievement and other life outcomes that have a relationship to cognitive ability.
Brief Intellectual Ability (BIA)
The BIA is based on Tests 1-3 and is best used as a screener or for re-evaluation purposes. Like 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. Because many cognitive tests now measure multiple abilities, it may be important to evaluation an individuals' functioning on more complex tasks versus simpler, more automatic 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:
Like the WJ V 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.
Summary