The unconscious may not be as powerful as Sigmund Freud thought, say researchers who found a way to show that subliminal messages do influence the human mind - but the influence lasts only a fraction of a second.
The study also casts doubt on the effectiveness of subliminal messages in advertising."The mind, when it's operating unconsciously, is not nearly so smart as Freud and other psychoanalysts would have us believe," said University of Washington psychology professor Anthony Greenwald.
The study by Greenwald and two assistants at the university's Seattle campus was published Friday in the journal Science. They offered a way to measure the effects of subliminal messages and showed that they only influence the mind for about one-tenth of a second.
"That's important because theories of how the mind operates unconsciously are used in devising psychotherapies," Greenwald said. "As we change our concept of how much the mind can accomplish unconsciously, we change our mind about what should work inside the therapy."
In their experiment, Greenwald's team jammed a name - the subliminal message - between two strings of letters and flashed it on a screen. Immediately afterward, they flashed a second name, called a target.
Some 300 student volunteers were asked to identify the target names as male or female. Researchers looked at what happened when the subliminal and target names were dissimilar - one male, one female.
When the time between seeing the subliminal and target names was just one-tenth of a second and the students had little time to respond, they often got the target name's gender wrong. That indicated the subliminal name had influenced them, steering them to the incorrect answer.
On the other hand, the students more easily identified the target name's gender if the interval between the subliminal and target names was longer and they had ample response time. That indicated the subliminal name's effect had not lasted beyond one-tenth of a second.
Purdue University psychology professor Eliot Smith said Greenwald's findings, which Smith has reproduced separately, put the idea of "subliminal effects" on a firm footing for the first time.
"While many of us in this research field have believed that these effects exist . . . they were still surrounded by some controversy, people who doubted their existence," Smith said.
Freud, the father of psychoanalysis, believed the unconscious performed powerful and complex feats, guiding social behavior and protecting the conscious mind from painful psychosexual truths.
"Our research reveals, instead, an unconscious mind that is limited to some very simple achievements," Greenwald wrote in materials accompanying the study. "The simple achievement that we investigated includes being able to analyze the meaning of a single word and to retain that word's meaning for just a tenth of a second."