INGESTED ETHANOL AND BINOCULAR-RIVALRY

Purpose. An early study claimed that ethanol ingestion can attenuate b inocular rivalry and, in some cases, may produce the phenomenal fusion of normally rivalrous stimuli. The current study examined those claim s in an experiment incorporating key controls that were lacking in the earlier study. Methods. There were two conditions, one in which obser vers consumed ethanol and the other in which they consumed a placebo. Observers reported the course of binocular rivalry for several hours a fter drink consumption using two types of rivalry stimuli, one consist ing of a continuously illuminated set of stimuli, the other consisting of dichoptic afterimages. Results. Ingestion of ethanol resulted in a decrease in rivalry alternation rates, although there was no evidence of phenomenal fusion. Results were essentially identical for both sti mulus types. Conclusion. It is suggested that this effect is not cause d by ethanol-induced changes in oculomotor mechanisms but may be cause d by ethanol-induced decreases in contrast sensitivity.