Detecting dissimulation: profiles of simulated malingerers, traumatic brain-injury patients, and normal controls on a revised version of Hiscock and Hiscock's Forced-Choice Memory Test.

Abstract

A computer-administered memory test was given to normal subjects instructed to feign brain damage, normal controls, and traumatic brain-injured (TBI) patients with complaints of memory dysfunction. The test, a revised version of an instrument developed by Hiscock and Hiscock (1989) employed forced, two-choice recognition of previously presented five-digit numbers. Two levels of item difficulty and three retention intervals were used. Control and TBI subjects performed at near ceiling level on easy items and items with short retention intervals. Feigning subjects performed worse than TBI and control subjects at all levels of item difficulty and all retention intervals. Subjects groups were maximally distinguishable from one another by performance on difficult items and items with the longest retention interval. All TBI patients performed at or above chance level. Only 15% of the feigning subjects performed below chance level on any section of the test. Jack-knifed discriminant function analysis correctly classified 83% of all subjects into their respective groups. Although evaluation of patient performance relative to chance probability is useful for indicating the presence of extremely exaggerated memory deficits, criteria derived from sample distributions of group scores were superior for evaluation of motivation in less obvious cases. The Victoria Revision may be useful for detecting true memory deficit as well as dissimulation.