During these long winter nights, you might find yourself visited by dead relatives.
Even if you can barely recall their faces, they can appear in dazzling, hi-def detail while you sleep. You might dream about your father in his mustard-yellow alpaca cardigan, or 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.
What's more, dreams seem to run on a subconscious calendar.
Even after the holidays, people from the past can rise from the depths, reeled in by thin threads tied to traditional family gatherings.
"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."
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.
But with the help of new technology, dream research has been advancing dramatically, said Bulkeley, one of the small cadre of researchers who collect data from computerized "dream banks."
Bulkeley said he has about 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 vs. 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."
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 8 ball."
And 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."
If anything, the study of dreams shows that even the most anxious and isolated among us are not so far afield. Nearly everyone has experienced a variation on dreams of being naked in public or unprepared for a test.
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 essay to pass the imperial examination.
Nearly 80 percent of recurrent dreams are negative, she said, but the dream response varies widely. Barrett 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 also exists in nearly every culture, researchers say. And while it has always provided fodder for those who claim to know how to unlock the mind's secrets, 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," said Bulkeley. "If anyone takes out a dictionary and tells you this is what your dreams mean, run the other way."