Figure 3.

Sample data from a trial in an individual subject (#1) for a rare trial block demonstrating both a directional and temporal asymmetry. The subject was shown visual motion at 90% coherence consistent with rotation. The task was to identify which interval was larger (MC). Results from 8 independent randomly interleaved staircases are shown. Each panel represents two staircases, one in which the variable interval started at a maximum value (29°) and the other at which it started at a minimum value (1°) which tended to converge to a similar PSE during the trial block. Data points are sized proportional to the number of stimulus presentations at each level. The value of the PSE in deg is given with the 95% confidence interval in parenthesis. In every panel, the PSE is positive indicating the first interval was larger than the second interval when they were perceived as equal. When similar stimuli in opposite directions are compared (A & D, B & D), the PSE was significantly larger when leftward motion was presented first (panels C & D). This indicates a directional asymmetry where the leftward stimuli were presented larger to be perceived as equal. The magnitudes of the variable stimuli at the PSE are shown. Panel A: The first interval is variable and to the right. Panel B: The first interval is fixed and to the right. Panel C: The first interval is variable and to the left. Panel D: The first interval is fixed and to the left.