Rate of optokinetic nystagmus to the left and right and performance on the portable Rod and Frame Test

Deviations from the true vertical on the Rod and Frame Test were studied in relation to optokinetic nystagmus response during varied mental activities in 14 right-handed male college students. Judgment of the vertical was more accurate for 7 subjects whose frequency of optokinetic nystagmus was high or low in both directions than for those 7 whose optokinetic nystagmus frequency was high in one direction and low in the other. Asymmetries in the degree to which subjects' optokinetic nystagmus frequency was raised during periods when they were instructed to perform presumed left-hemisphere mental tasks were related to asymmetries in their Rod and Frame Test performance.