Noncredible Explanations of Noncredible Performance on Symptom Validity Tests 5

Neuropsychologists measure brain function using standardized tests, or, at least that is the intention. For generations, it was assumed that differences in cognitive ability from one person to another were accurately mirrored by differences in cognitive test scores, although not perfectly because there was some random error. It was assumed that, in nearly all cases, people being administered cognitive tests were trying their best and that low scores reflected low abilities in nearly all cases. Scores in the impaired range were readily interpreted as signs of cognitive deficits and impaired brain function. Error was assumed to be just as likely to lead to an overestimate of brain function as to an underestimate. Only relatively recently was it shown that the assumption that people are trying their best is often wrong, and that low scores frequently do not signify low ability at all because the data are simply invalid (e.g., Fox, 2011; Green, Rohling, LeesHaley, & Allen, 2001; Meyers, Volbrecht, Axelrod, & Reinsch-Boothby, 2011; Stevens, Friedel, Mehren, & Merten, 2008). Invalid test results from poor effort or deliberate underachievement do not occur only in groups where there is an obvious external incentive to appear cognitively impaired, such as those seeking financial compensation for cognitive impairment. Even in groups previously assumed to be highly motivated to do well, effort may be poor, leading to invalid test results. For example, it was assumed that professional athletes being tested cognitively at baseline and then after concussions would try their best. Their motivation was to carry on playing and earning a living. The assumption of valid data and good effort was disproven when an American professional football player, Peyton Manning, admitted that he had deliberately performed poorly at baseline so that his scores after a concussion would look as if there was no impairment, and other players admitted that this was a commonly-used tactic to manipulate the test scores in their favor (Fox59 Sports Staff, 2011). Neuropsychologists now know that, in many different contexts, effort can be low to a degree that is sufficient to invalidate test results, especially if there is an incentive to appear impaired (e.g., Chafetz, 2008; Chafetz, Prentkowski, & Rao, 2011; Flaro, Green, & Robertson, 2007; Sullivan, May, & Galbally, 2007). For that reason, effort testing is increasingly recognized as an essential component of neuropsychological testing (Bush et al., 2005; Heilbronner, Sweet, Morgan, Larrabee, & Millis, 2009).