APA Dictionary of Psychology

in parapsychology experiments using Zener cards or similar targets, a supposed difference in outcomes found between trials involving participants who believe that they may succeed in the given task (sheep) and trials involving those who assume that this is impossible (goats). See also decline effect; differential effect; focusing effect; position effect; preferential effect. [coined by U.S. parapsychologist Gertrude Schmeidler (1912–2009)]