"And I Feel Like I've Been Here Before"

In his 1863 travelogue Our Old Home, Nathaniel Hawthorne described a visit to Stanton Harcourt, a 15th century manor house near Oxford, England. As he stood in the building’s enormous medieval kitchen, the writer recalled, he was washed over by an eerie sensation: “I was haunted and perplexed by an idea that somewhere or other I had seen just this strange spectacle before. The height, the blackness, the dismal void, before my eyes, seemed as familiar as the decorous neatness of my grandmother’s kitchen.”

Hawthorne had never been to Stanton Harcourt before, yet his “memory” was specific and palpable and emotional. Writers from St. Augustine to Dickens to Proust have described similar sensations of having been somewhere before—impossibly—and indeed that is the accepted meaning of the psychological phenomenon commonly known as déjà vu.

And it is common: Fully a third of us report having had a déjà vu experience, and the real number may be much higher. Such experiences have over the years been attributed to everything from past lives to subterranean erotic impulses to neurological disorders, but those ideas have all been discarded. Today there is scientific consensus that déjà vu is a false memory experience: Our brains are registering novel perceptions of the world as old and familiar, even when all evidence says they cannot be.

But why? New insights into the mechanics of memory and cognition are helping to answer that question. The brain is now viewed as something of a hybrid engine, a dual processor that divides its work between rapid, automatic decisions and more deliberate judgments. It toggles back and forth constantly, and as it does it uses two different kinds of recognition: recall and familiarity.

Think of an everyday memory experience. The first kind of recognition is simple recall. You run into a woman at the market who you met at a party the night before, and you clearly recollect that first meeting: “Hi, Annie. We met at Jerry’s party last night, over by the bar.” That’s simple recall; something happened and you remember it pretty much as it happened.

The second kind of recognition is much fuzzier, based only on a vague sense of familiarity. That’s because many of the memories we put down are not finely detailed, but rather just the gist of an experience: Jerry’s party, lots of new people milling around with drinks, not much more in the way of detail. So when you run into Annie at the market, she’s only vaguely familiar. You can’t place her. Do you know her from the mailroom at work?

Déjà vu experiences are just an aberration of this normal recognition experience. Or at least that’s the theory, which psychologists have recently begun testing in the laboratory. Here’s an example. Colorado State University psychologist Anne Cleary had volunteers study a long list of celebrity names. Later on, she showed them a collection of celebrity photographs. Some photos corresponded to the names, but others did not. The volunteers did two things: They tried to identify the celebrities in the photos, and they also said how likely it was that they had studied the name of each celebrity earlier.

The findings were interesting. Even when they could not identify a celebrity by the photo, they often had a sense of which names they had studied earlier and which they had not. That is, they couldn’t identify the source of their familiarity with the celebrity, but they knew the celebrity was familiar to them. Cleary ran the same experiment with famous places, like Stonehenge and the Taj Majal, and got the same result.

Apparently the volunteers had stored at least a trace of memory, but it was sufficiently fuzzy that they weren’t consciously aware of the link to the new experience. But what exactly did they store in memory that would trigger the feelings of familiarity? Cleary suspects that even very subtle features of an experience can be enough to cause a later sense of remembering. In another experiment, she had volunteers study a random list of words: raft, eighty, and so forth. On a later recognition test, some of the new words resembled the earlier words only in their most general shape and sound: Laughed might echo raft, for example, or lady might echo eighty. When old and new words overlapped on this very subtle feature, volunteers again reported a sense of familiarity with the novel word.

Presumably the same illusion can occur with more elaborate perceptions and experiences. As Cleary reports in the October issue of Current Directions of Psychological Science, some people report a sense of familiarity with completely new pictures based only on a visual fragment from an earlier experience. A single geometric shape, for instance, can create the sense that an entire new scene has been experienced before.

That is almost certainly what happened with Hawthorne in the kitchen. Recall that it was the “height” and “blackness” of the room that stirred his global memory of having been there before. Indeed, Hawthorne figured this out himself, without the tools of modern memory research. He later summoned up a dim memory of a poem by Alexander Pope, who had also been moved to write about the cavernous rooms of Stanton Harcourt.

For more insights into the quirks of human nature, visit the “We’re Only Human” weblog at www.psychologicalscience.org/onlyhuman. Selections from the blog also appear in the magazine Scientific American Mind and at http://www.sciam.com/.