Fig. 2.

Adaptive perceptual threshold tracking. A representative tracing is shown for the vestibular-only condition at 0.5 Hz. Each circle indicates 1 trial in which the participant had to identify the direction (right or left) in which they perceived motion. Testing began at 10°/s, a suprathreshold angular velocity, and was reduced in a 2-down-1-up manner. 2 consecutively correct responses led to a decreased stimulus amplitude, and 1 incorrect response increased the amplitude of the following stimulus. Each test continued until there were 7 reversals in the adaptive track. Reversals are defined as a trial in which a directional change in the track occurred. Open circles denote reversals, and open circles with crosses indicate the last 6 reversals that were averaged to determine an individual perceptual threshold (dashed line).