During rotational stimulation Ss were instructed, in different test sessions, to (a) do mental arithmetic, (b) make estimates of subjective velocity, (c) reproduce durations of sound stimuli, and (d) assume a state of reverie. The reverie state resulted in significantly less recorded nystagmus than the other three tasks, while mental arithmetic was the most efficacious means of obtaining a vigorous response. A factor of sustained alertness seems to be an important condition for the maintenance of nystagmus.