Fig. 1.

Top: schematic of Levelt's fourth proposition (L4). Bottom: 1 example of the percept duration dependence on stimulus strength as predicted by mutual inhibition models of binocular rivalry. Specifically, the models predict that increasing stimulus strength first yields increasing-duration (ID) followed by decreasing-duration (DD), while L4 proposes only DD behavior down to arbitrarily small stimulus strengths. Changes in model parameters can alter the shape of the curve at bottom, but the mathematical equations of mutual inhibition models seem to guarantee the existence of both ID and DD behavior.