WHAT ON EARTH IS DEJA VU???

 

Watching the summer's events unfold - war protests, an Olympics scoring scandal, numerous terror scares - some people may have felt that it was all very familiar, that they had somehow been through this before.

Yet psychologists say it is usually life's more mundane details - the click of a radiator, the play of the shadows on a tablecloth - that prompt that sudden and sometimes breath-taking sense of familiarity.

"The way the coffee cups were lined up on the table," said Gretchen Purcell, 24, a business consultant in the Washington area who felt this so strongly during a conference-call meeting last month that it made her laugh out loud. "The whole scene was so familiar I thought I knew what people were going to say before they said it. It was like I was in a movie I'd already seen."

French for just that ("already seen"), déjà vu is the sort of fleeting, intimate experience that reveals itself more readily to novelists than to researchers. As recently as the 1990's, social scientists doing population surveys asked about it in the same breath as they inquired about poltergeists and contact with the dead.

But new research on memory has opened a promising window on the phenomenon, providing both possible explanations for the sensation and novel ways to create and measure it.

"It has been either ignored or considered too spooky or flaky for many scientists to touch," said Dr. Alan Brown, a psychologist at Southern Methodist University in Dallas, who reviews the history of the field in a new book, "The Déjà Vu Experience: Essays in Cognitive Psychology.'' "But it is real, and by bringing it into the lab we can at least begin to understand it."

In surveys, about two-thirds of adults report having had at least one déjà vu experience, and the odd sensation seems to occur most often in people with lively, frequently stimulated imaginations. People who travel a lot are more likely to report the experiences than homebodies, for instance, and those with college or advanced degrees report having it more often than others, perhaps because they have encountered its sweet strangeness in the literary accounts of Proust and Tolstoy - or are more likely to rent the movie "Groundhog Day." Rates seem to peak in young adulthood and to fall off gradually through retirement age, when, Dr. Brown suggests, many people live daily routines that really are familiar.

A century ago, when Freud's theories dominated the field of psychiatry, analysts cast déjà vu as evidence of unconscious conflict, the ego defending itself against upsetting erotic urges for a mother figure or other hidden desires. And for decades, doctors have reported that sensations of déjà vu occasionally precede the seizures suffered by people with epilepsy. Overactive circuits in the temporal lobe, which can cause seizures, may inappropriately stimulate regions of the brain involved in detecting familiarity, some doctors say.

But Dr. Brown and others argue that it is not necessary to invoke hidden conflicts or unusual brain conditions to explain many cases of déjà vu. Normal, healthy brain function suffices. For one thing, déjà vu appears to be more common when people are exhausted or stressed, conditions that are known to cloud short- and long-term memory (and that may also accompany jamais vu, the opposite experience of staring at familiar words or objects and having no recollection of them).

Debbie O'Leary, 40, a writer in Bloomington, Ind., said that some years ago she felt sensations of déjà vu while sick at home, as if her life had become a scratched record, with the same chorus repeating.

"It was literally like my brain was stuttering, like the same tape kept replaying the same thoughts, the same motions," as if time were stuck, she said. "I think it was the fatigue, the fever."

Psychologists have long known, too, that people register impressions and images well before they are aware of what they have seen. The brain sends visual signals through at least two circuits, which move from the retina through the brain to the visual cortex via different routes.