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Subliminal Perception.

Research on subliminal perception investigates whether subjects can unconsciously perceive stimuli that do not extend the absolute threshold. In a study that demonstrated the emotional impact of subliminal stimulations a device called a tachistoscope was used to flash the slides of strangers to subjects too briefly (only a tiny fraction of a second) to exceed the absolute threshold. Because previous research had shown that we prefer stimuli with which we are familiar, the experimenters predicted that if subliminal perception exists, the subjects would later express more positive feeling toward people whose photographs had been presented subliminally.

Given that we may be able to perceive subliminal stimuli and that we prefer stimuli with which we are familiar, could manufacturers make us like their products more by repeatedly presenting us subliminal messages about them? This is a heart of a controversy that has lasted since the late 1950s: Can subliminal advertising make people buy particular products? The controversy began after a marketing firm repeatedly flashed the words Eat Popcorn and Drink Coca-Cola during movies shown at a theatre in Fort Lee, New Jersey. Though those watching the movies could not detect the advertisements, after several weeks, popcorn sales had increased 50% and Coke sales had increased 18%. However, psychologists pointed out that the uncontrolled conditions of the study made it impossible to determine the actual reason for the increase in sales. Perhaps sales increased because better movies, hotter weather, or more appealing counter displays attracted more customers during the period when subliminal advertising was used.

More recently, parents of teenagers have expressed concerns about the alleged subliminal messages in rock music recording, such as Led Zeppelin’s “Stairway to Heaven”, that supposedly can be heard clearly when the recording is played backward. Despite the lack of evidence that such messages exist, fear that they might cause crime, Satanism, and sexual promiscouty led California and other states to pass laws requiring warnings on recordings that contained subliminal messages. Yet even if recording (or movies) contain subliminal messages, there is no evidence that listeners will obey them like zombies anymore that they will obey messages of which they are aware.

But what of the popular subliminal self-help audiotapes that supposedly help you to do everything from increase your grades to decrease your weight? They, too, have been evaluated scientifically. In a study of university students, one group listened to sounds of ocean waves that masked subliminal messages promoting good study habits. A second group listened to a placebo audiotape of ocean waves with no subliminal messages. And a control group listened to neither. At the end of the study, the groups didn’t differ in their final-exam grades or in their grade point averages. studies like this on indicate that you would be wise to spend less money on self-help tapes and more time on studying.