Normal volunteers: Who are they?

Twenty-one NIH normal volunteers, who had previously participated in risky, invasive biomedical research experiments were compared to twelve volunteers for less invasive and risky experiments. Comparisons used measures of personality (MMPI-2), social support (The Social Support Questionnaire), motivation for participation, and ratings of riskiness and invasiveness for a sample of actual research protocols. There were few differences between the two groups. However, when both groups' data were combined, NIH normal volunteers showed a markedly defensive or "faking good" profile on the MMPI-2, with numerous subscales found to be significantly lower than those of the test's normative sample. Although NIH volunteers showed no evidence of obvious psychopathology, in view of their defensiveness, it cannot be concluded that they are in fact free of pathology. Physiological measures or self-report scales not probing for psychopathology may reduce defensiveness and thus provide more information.