Traumatic brain injury is the most common cause of neurological disorder in the United States, with an annual incidence of over 1.5 million cases. Although acute space occupying lesions may be visualized by radiographic methods such as CT or MRI, diffuse shearing of neuronal projections is thought to be the primary cause of chronic cognitive impairment caused by traumatic brain injury. Axonal shearing occurs at the microscopic level and cannot be directly visualized by radiographic methods. Objective diagnosis of chronic intellectual impairment typically involves examination with the Wechsler Adult Intelligence Scale-3 (WAIS-3). Traumatic brain injury may significantly reduce IQ, and differentially affect component abilities such as short term memory and reasoning. In clinical settings the extent of intellectual impairment cannot be predicted by existing radiographic methods, and must be directly tested with the WAIS-3. Test results are used by physicians to make judgments about prognosis and treatment. IQ tests are also used by the courts to determine the amount of compensation awarded in personal injury litigation and for determinations of criminal competence and sanity. Attempts to exaggerate or malinger intellectual impairment are frequent in these cases, and account for about 40% of litigating or compensation seeking head trauma claims. The current study is designed to provide an empirically tested method for identification of malingered intellectual impairment. The WAIS-3 will be administered to 40 individuals who have sustained medically documented brain injury, and 40 normal neurologically subjects who simulate deficient intelligence. Test scores will be statistically analyzed by stepwise discriminant function analysis. This will produce an algebraic equation capable of making differential diagnoses between actual and malingered impairment in IQ. The resulting procedure can be applied to clinical cases to determine if intellectual impairment is present or exaggerated.