The use of symptom validity testing in the diagnosis of functional sensory and memory deficits: a review

This paper reviews the use of a modern psychophysical technique known as symptom validity testing. The technique employs a forced choice procedure providing an objective method for distinguishing between functional and organic aetiology in cases with sensory or memory deficit. The determination of functionality is by the objective demonstration that behaviour is controlled by stimuli in the sense modality in which the deficit is claimed. The data can be evaluated using conventional statistical techniques. The method is an advance on classical psychophysical methods as it does not depend upon the patient reporting whether he can or cannot perceive a single stimulus.