“…When observers merely judge which of two stimuli predominates during a given observation period, the possibility of criterion effects cannot be ruled out. Some studies attempted to minimize this problem by using shorter exposure times (e.g., Hastorf & Myro, 1959; Rommetveit, Toch, & Svendsen, 1968a, 1968b), but as a consequence observers may have experienced dichoptic masking, not binocular rivalry. Rivalry requires anywhere from several hundred milliseconds to several seconds to develop (Goldstein, 1970; Liu, Tyler, Schor, & Lunn, 1990; Wolfe, 1983), so when exposure times are extremely brief one must question whether rivalry occurs at all.…”