Are verbal intelligence subtests and reading measures immune to non-credible effort?

The validity of neuropsychological testing is reliant on examinees putting forth adequate effort, yet it has been asserted that verbal subtests from the Wechsler Adult Intelligence Scales (WAIS) are insensitive to suboptimal effort in comparison to other commonly used neuropsychological measures. The current study examined performance differences on the entire WAIS-IV and WRAT-4 Reading, as well as the CVLT-II and several WMS-IV subtests, in 207 Veterans classified into Credible Effort (n = 146) and Non-credible Effort (n = 61) groups. Analyses revealed that the Non-credible Effort group performed significantly lower on all examined measures including verbal tests, with moderate to large effect sizes observed for most tests. Current findings thus indicate that WAIS-IV verbal subtests and reading ability measures, such as on the WRAT-4, are not insensitive to effects of non-credible effort. Consequently it is recommended that these tests not generally be used to estimate baseline intellectual functioning when found in the presence of non-credible effort. While there was broad performance suppression across all measures examined, results also showed a distinct continuum of test susceptibility with some measures being more or less sensitive to inadequate effort. Recommendations for future performance validity test development are presented.