[A test of symptom validity in assessing functional symptoms].

Symptom Validity Testing was developed to evaluate complaints of sensory deficits. The assessment is based on the inability of patients to perceive a sensory signal. Subjects must guess the signal using the model of coin flipping (head or tail). The signals are presented randomized in an equal number of alternatives. A 50-percent hit-rate for enough trials is expected in a true sensory deficit. Deceptive patients are expected to perform a hit-rate below the probabilities of chance.