The Broca-Sulzer phenomenon refers to the fact that the phenomenal brightness of a stimulus can be diminished by the unchanged continuation of the stimulus itself. The reaction time of humans has been used to measure this phenomenon. The present study shows that RT is unrelated to flash duration between 10 and 500 msec. when durations presented in random order. Earlier results showing faster RT to 50-msec. flashes than to longer ones are attributable to attitudinal factors due to blocks of trials. From Psyc Abstracts 36:01:1CD93R. (PsycINFO Database Record (c) 2006 APA, all rights reserved)