Psychophysiologic test performance in normal twins and in a pair of identical twins with essential tremor that is suppressed by alcohol.

In a sample of 52 adults male twin pairs (26 MZ, 26DZ) performance in a series of psychophysiologic tests was measured. The intraindividual variability was determined by repetitive tests in the same subjects. In a number of cases the measured parameters proved relatively stable within the same peron; identical twins, however, were no more similar to one another than fraternal twins. In a pair of identical twins with autosomal-dominant essential tremor the degree of the tremor could be effectively reduced by alcohol application.