The Relation Between Intellectual Functioning and Adaptive Behavior in the Diagnosis of Intellectual Disability.
Treat IQ and daily-life skills as two separate lanes when you diagnose or plan therapy.
01Research in Context
What this study did
Faso et al. (2016) wrote a position paper. They looked at how doctors decide if someone has intellectual disability.
The authors said IQ scores and daily-life skills are two separate things. They warned not to treat low IQ as the cause of poor adaptive behavior.
What they found
The paper found no proof that low IQ directly hurts daily living skills. It told teams to weigh both areas equally when they diagnose.
In short, stop guessing that a low score on an IQ test explains why a person cannot cook or count money.
How this fits with other research
Later work backs this up. Drijver et al. (2025) built the DIAB, a new tool that gives reliable adaptive scores for adults with moderate to profound ID. It lets clinicians give daily-life skills the same spotlight IQ already gets.
Balboni et al. (2020) went further. In a large group of people with severe ID plus other disorders, those who showed more daily skills also showed more problem behavior. This odd pairing supports the paper’s point: adaptive behavior is its own domain, not just a side effect of IQ.
Anonymous (2020) flipped the idea forward. Because IQ and adaptive scores are separate, old norm-referenced tests are poor yardsticks for treatment trials. The review urges researchers to pick new outcome measures that can actually show change.
Why it matters
For BCBAs this means write separate goals for intellectual learning and daily living. Do not drop adaptive targets just because IQ is low, and do not assume good IQ protects against adaptive gaps. Use tools like the DIAB or cognitively friendly self-reports to track real-world skills on their own track.
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02At a glance
03Original abstract
Intellectual disability originates during the developmental period and is characterized by significant limitations both in intellectual functioning and in adaptive behavior as expressed in conceptual, social, and practical adaptive skills. In this article, we present a brief history of the diagnostic criteria of intellectual disability for both the DSM-5 and AAIDD. The article also (a) provides an update of the understanding of adaptive behavior, (b) dispels two thinking errors regarding mistaken temporal or causal link between intellectual functioning and adaptive behavior, (c) explains that there is a strong correlational, but no causative, relation between intellectual functioning and adaptive behavior, and (d) asserts that once a question of determining intellectual disability is raised, both intellectual functioning and adaptive behavior are assessed and considered jointly and weighed equally in the diagnosis of intellectual disability. We discuss the problems created by an inaccurate statement that appears in the DSM-5 regarding a causal link between deficits in intellectual functioning and adaptive behavior and propose an immediate revision to remove this erroneous and confounding statement.
Intellectual and developmental disabilities, 2016 · doi:10.1352/1934-9556-54.6.381