During these long winter nights as the holidays flash by, you might find yourself visited more often by dead relatives.

Even if you can barely recall their faces, they can appear in dazzling hi-def detail while you sleep.

Not only might you dream about your father in his mustard-yellow alpaca cardigan, but you might even detect the clove scent of his aftershave and hear his gravelly voice telling you to dump your girlfriend.

"The brain definitely has this amazing capacity to create an entirely lifelike experiential reality in our dreams," said Kelly Bulkeley, former president of the International Association for the Study of Dreams in Berkeley, Calif.

It also seems to run a subconscious calendar. People from the past can rise from the depths, reeled in by thin threads tied to the holidays.

"People are gathering this time of year. There definitely is a circumstantial trigger," Bulkeley said. "This is what dreams do - they keep us connected to our roots as they try to imagine where our future lies."

Using a new wealth of information, he said, studies are revealing the remarkable commonality of recurrent dreams. Most are negative. Children tend to dream about being chased by monsters or animals, but adults are haunted mostly by failed exams and fear of forgetting to get dressed.

And yet, the more dreams are studied, the clearer it becomes these thoughts from the mists of the mind are as deeply personal as they are mysterious.

The study of dreams dates back centuries. Aristotle believed them to be demonic. Freud interpreted them as a glimpse into the unconscious. One of the first quantitative studies was done by Mary Whiton Calkins, a psychologist at Wellesley College in the early 1900s.

Dream research has been advancing dramatically with help from new technology, said Bulkeley, one of the small cadre of researchers who collect data from computerized "dream banks."

Last he checked, Bulkeley had 14,000 dreams in his personal collection, much of which is shared with colleague G. William Domhoff of the University of California, Santa Cruz. Domhoff has more than 30,000 in his bank.

Using computers, they sift through the data looking for patterns, key words, and images.

"In the past, if a dream researcher wanted to analyze the difference between the way the blind dream versus the sighted, if they collected 200 dreams, that was considered a good-sized sample," said Deirdre Barrett, associate professor of psychology at Harvard Medical School and author of The Committee of Sleep, about how artists, scientists, and athletes use dreams to solve problems.

Now, with tens of thousands of dreams in the bank, Barrett said, "there are all these samples that allow you to pick out tiny elements of dream content. We can select for rare medical conditions and study how do the dreams vary."

A recent study in Japan, she said, has used technology to create videos reflecting the content of dreams. Researchers recorded brain-wave patterns as each subject looked at pictures of animals, people, and objects. They then looked for correlating patterns when the subject was asleep, and converted them into visual images.

"It was the coolest-looking thing," Barrett said.

Dream research has remained a small domain because its advancement does not seem to have direct clinical applications, with the exception, she said, of post-traumatic distress nightmares and a few other rare disorders.

Dreams can serve as a "therapeutic ally," giving clues about the nature of anxieties, frustrations, and desires. "But it's not a magic eight ball."

Some of Barrett's work has looked at the practical implications of dreams.

"People dream solutions to architectural designs or chemistry, writers dream plots for novels, musicians hear scores. Just about any practical human pursuit can get a huge breakthrough in a dream," Barrett said. "If we're in a rut and not seeing a solution, dreams can show us a way outside of the box."

Those who may suffer existential angst, feeling isolated and alone in their suffering, might consider the ties that bind nearly all of humanity: Recurrent dreams of being naked in public and showing up in a panic unprepared for a test.

Nearly everyone has had variations of both.

The test dream, Barrett said, dates to at least the 15th century, when Chinese candidates for coveted positions in the government bureaucracy had to master a complex "eight-legged essay" to pass the imperial examination.

Nearly 80 percent of recurrent dreams are negative, she said.

Whatever variation an individual has tends to remain consistent, she said. And the range of those variations is as diverse as the human race.

She has heard of dreams in which a man is mortified to find himself in a mall without shoes and he tries to keep to the shadows to hide his bare feet. Others, she said, may find themselves stark naked on a busy city street and decide to saunter nonchalantly as though nothing were amiss.

Dream interpretation exists in nearly every culture, researchers say. And it has always provided fodder for those who claim - out of sincere religious or cultural belief or roguish scheming - to know how to unlock the mind's secrets.

The one truth that remains constant, Bulkeley said, is the only expert about your dreams is you.

"People can give you helpful advice, but it's always up to the dreamer to say this is what I think it means," he said. "If anyone takes out a dictionary and tells you this is what your dreams mean, run the other way."

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