Fig. 2.

Sequence of answers provided by a subject over the course of one run using a “3-down, 1-up” adaptive paradigm. Each trial is indicated by a circle. A subject must answer correctly three times in a row before the comparison stimulus is reduced one step closer to the reference to make the task more difficult. A single error increases the comparison stimulus by an equal amount. Reversals are indicated by open circles. For reference velocities greater than or equal to 20 deg/s, the first five reversals are thrown out and the subsequent nine are averaged to determine the threshold. For reference velocities of 0 deg/s (detection threshold), the first nine reversals are averaged to determine the threshold