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Embedded validity indicators (EVIs) derived from motor tests have received less empirical attention than those derived from tests of other neuropsychological abilities, particularly memory. Preliminary evidence suggests that the Grooved Pegboard Test (GPB) may function as an EVI, but existing studies were largely conducted using simulators and population samples without cognitive impairment. In this study we aimed to evaluate the GPB's classification accuracy as an EVI among a mixed clinical neuropsychiatric sample with and without cognitive impairment. This cross-sectional study comprised 223 patients clinically referred for neuropsychological testing. GPB raw and T-scores for both dominant and nondominant hands were examined as EVIs. A known-groups design, based on ≤1 failure on a battery of validated, independent criterion PVTs, showed that GPB performance differed significantly by validity group. Within the valid group, receiver operating characteristic curve analyses revealed that only the dominant hand raw score displayed acceptable classification accuracy for detecting invalid performance (area under curve [AUC] =.72), with an optimal cut-score of ≥106 seconds (33% sensitivity/88% specificity). All other scores had marginally lower classification accuracy (AUCs =.65–.68) for differentiating valid from invalid performers. Therefore, the GPB demonstrated limited utility as an EVI in a clinical sample containing patients with bona fide cognitive impairment. [ABSTRACT FROM AUTHOR]