Fig. 2.

Contrast perception peaks with stimulus duration. (A) Psychometric curves, averaged across subjects (n = 9) for the unblocked and blocked experiments, with a 50-ms duration standard and a 40% contrast comparator (see Figs. S1 and S2 for full results). The unblocked results follow Broca and Sulzer’s predictions, whereas the blocked results are consistent with Bloch’s law. (B) PSE for the comparator as a function of its duration (average ± SE from the mean). The unblocked results (green) reveal a peak in perceived contrast as a function of duration. The blocked results (gray) indicate that Bloch’s law is an artifact of uncontrolled intrinsic expertise bias. Horizontal bar at top indicates the range of durations showing a statistically significant difference between the unblocked and blocked experiments.