Failure to inhibit the reading response on the Stroop Test: a pathognomonic indicator of suspect effort.

We present 6 patients who displayed noncredible effort on neuropsychological testing (verified by failures on specialized measures designed to discreetly assess effort status and multiple behavioral inconsistencies) and complained of complete illiteracy secondary to impoverished educational history, learning disability, or acquired brain injury. The Stroop Test, a measure of a specific aspect of executive function requiring inhibition of an automatized oral reading response in favor of a less habitual, competing color-naming response, was administered to these patients. All six subjects claimed that they were unable to perform the Word-Reading trial as a consequence of total reading disability, but on the Color-Word Interference trial, they all committed "errors" by reading the written words. Five of the six subjects also performed substantially slower on the Interference condition relative to the Color-Naming trial, indicating that they were in fact inhibiting a reading response. However, in cases involving complaints of complete reading illiteracy, the observation of these individuals performing an act that they claimed to be unable to do was the most powerful and pathognomonic indicator of deliberate feigning or exaggeration of impairment in these cases.