The implications of symptom validity test failure for ability-based test performance in a pediatric sample.

276 children aged 8-16, consecutive outpatient neuropsychology referrals after mild TBI

US children 8-16 referred after mild traumatic brain injury; overlaps an earlier case series (Kirkwood & Kirk 2010) that also included 17-year-olds.

Consecutive clinical case series with an objective validity test (Medical Symptom Validity Test) administered alongside the ability battery. Not randomised and not a general-population sample - these are clinically referred children after head injury, so the 19% failure rate is a clinical base rate, not a school-testing one. The variance-explained figure is a correlation and does not establish that invalid effort CAUSED the low ability scores rather than sharing a cause with them.

The single most useful number in this cluster for an intake tool. Nineteen percent of school-aged children failed the MSVT using adult-derived cutoffs - one child in five, in a sample with no obvious secondary gain. NO background or injury variable distinguished the failers from the passers, so there was no way to predict from the file who would produce an invalid score. Validity-test performance correlated significantly with EVERY ability-based test and explained 38% of total ability-test variance, with large effect sizes across nearly all measures. In other words: whether the child was trying is a bigger determinant of the score profile than most of what the profile is read as measuring.

Low relevance. The finding is about measurement validity, not about a heritable trait; if anything it cuts against genetic explanation, since the failure was unpredictable from any child or injury characteristic.

Builds on and extends Kirkwood & Kirk (2010) in the same case series; consistent with the wider pediatric performance-validity literature showing children can pass adult-cutoff validity tests, so failure is informative rather than developmental.