Relationship between the Vineland Adaptive Behaviour Scales and the Wechsler Adult Intelligence Scale IV in adults with intellectual disabilities.
IQ and daily-living skills stay separate in adults with ID, so always measure both.
01Research in Context
What this study did
The team gave the adults with intellectual disability two tests. One was the WAIS-IV IQ test. The other was the Vineland Adaptive Behavior Scales interview.
They ran simple correlations to see if IQ scores matched daily-living scores.
What they found
IQ and Vineland scores hardly lined up. Most correlation numbers were below 0.30, which is weak.
High IQ did not mean high adaptive skills, and vice versa. The two tools measure different things.
How this fits with other research
Whitaker (2008) shows IQ in low-functioning adults is usually stable. Dudley et al. (2019) add that, even when IQ is steady, adaptive skills can sit anywhere on the scale.
Green et al. (2020) found Vineland-3 gives lower scores than Vineland-II. Together with M et al., this warns us: a drop in Vineland scores may be the edition, not real skill loss.
Mazur et al. (1992) saw stable WAIS-R scores over 2.5 years. M et al. now say those stable IQs still won’t predict self-care or social skills.
Why it matters
Keep testing both IQ and adaptive behavior. One number can’t tell you if a client can cook, shop, or keep a job. Use Vineland for programming goals and WAIS-IV for cognitive strengths. If you switch Vineland editions, expect lower scores and don’t panic.
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02At a glance
03Original abstract
BACKGROUND: Diagnoses of intellectual disability (ID) are based on three criteria: significant impairments in intellectual functioning, concurrent deficits in adaptive behaviour, and both being acquired in the developmental period. Adaptive behaviour was formally incorporated into the diagnosis in 1959; the rationale being that IQ and adaptive behaviour were different constructs that independently contribute to the diagnosis. However, there are limited data on the relationship between IQ and adaptive behaviour and especially so for adults who have ID. The aim of this study was to investigate this relationship on two widely used assessment tools: the Wechsler Adult Intelligence Scale - fourth edition (WAIS-IV) and the Vineland Adaptive Behaviour Scales (VABS). METHOD: Data were extracted from the case files of 147 adults who had a formal diagnosis of ID based on the WAIS-IV and VABS. Internal consistency was computed and compared to general population data. Correlations between the WAIS-IV and the VABS were computed. RESULTS: Internal consistencies for the tests when used with adults who have ID were generally good. The correlations between the WAIS-IV and VABS composite and subdomain scores were all low and similar to those reported for the general population. CONCLUSION: These results suggest that the WAIS-IV and VABS are measuring different constructs that contribute to the diagnosis of ID. Unfortunately, by the time such data have been collected, tests are being revised. The Vineland has now been revised and is in its third edition, but no data on the relationship between IQ and the VABS were collected during test development. The WAIS-V is now in development, and so it is recommended that such work be incorporated into this process or shortly thereafter to ensure that the tools continue to access independent constructs.
Journal of intellectual disability research : JIDR, 2019 · doi:10.1111/jir.12610