Investigating the structure and invariance of the Wechsler Adult Intelligence Scales, Fourth Edition in a sample of adults with intellectual disabilities.
The WAIS-IV keeps its four-factor structure in adults with ID, so you can interpret the scores just like you do for typical clients.
01Research in Context
What this study did
McGeown et al. (2013) asked a simple question. Does the WAIS-IV still measure the same four abilities in adults with intellectual disability as it does in everyone else?
They gave the full battery to adults with ID and to matched controls. Then they ran factor checks to see if the four-factor shape held.
What they found
The four WAIS-IV factors stayed intact. The same Index scores—Verbal Comprehension, Perceptual Reasoning, Working Memory, and Processing Speed—fit the ID group just like the control group.
In plain words, the test measures the same things, so you can read the scores the same way.
How this fits with other research
Symons et al. (2005) already showed that short Wechsler forms work well in high-functioning autism. McGeown et al. (2013) now extends that good news to adults with ID using the full WAIS-IV.
Lawer et al. (2009) found that circumplex personality scales keep their shape in ID. The new IQ data line up with that pattern: mainstream tests hold their structure.
Mottron (2004) warned that non-Wechsler IQ tools overestimate ability in autism. The current study quietly backs that stance—stick with Wechsler instruments when you need valid scores.
Why it matters
You can give the WAIS-IV to adult clients with ID and trust the Index profile. If Working Memory Index is the lowest, you can target memory strategies without wondering if the test “means something else” in this population. Use the same score cut-offs, write reports with the same language, and compare clients to norm tables without extra caveats.
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02At a glance
03Original abstract
Recent research has questioned whether the Wechsler Adult Intelligence Scales (WAIS) measure the same constructs for adults with intellectual disabilities as they do for the general population (MacLean et al., 2011). Using the special validity sample of the WAIS-IV (Wechsler, 2008b), the structure of the WAIS-IV was investigated using confirmatory factor analysis and tested for measurement invariance across a sample with intellectual disabilities and a control group matched in demographic characteristics. The instrument demonstrated strong factorial invariance when the standard subtests were used. When the standard and supplemental subtests were included in the model, the WAIS-IV four-factor structure provided a model of measurement for the Subtest Scores in the intellectual disability group, but the Perceptual Reasoning factor demonstrated differentiation into Fluid Reasoning and Visual-Spatial factors in the matched control group. In general, the research findings suggest that the four-factor structure of the WAIS-IV is invariant across the intellectual disability and matched control groups.
Research in developmental disabilities, 2013 · doi:10.1016/j.ridd.2013.06.029