Modern-day people think of themselves as a calm, cool, rational crew. But when it comes to an everyday belief in superstition, it turns out they're not all that different from their ancestors of the Middle Ages. They may not still believe that toads cause warts or that when teenage girls lose their virginity, tiny clefts in the ends of their noses disappear, but plenty of other illogical notions remain.

Recently, for example, members of the psychology department at Pierce College in Los Angeles flew into an uproar when the administration assigned the number 1300 to their building; they were afraid that superstitious students would refuse to take psychology courses there.What with microwave radiation, AIDS and complex technologies, there are many unprecedented things to be superstitious about. The only difference is, people today don't so much call them superstitions anymore as valid psychological insights or hard-won strategies for coping with urban life.

IT'S A WARM MORNING in the overstuffed folklore archives at the University of California, Los Angeles, and Frances Cattermole-Tally, a busy but friendly folklorist and executive editor of the "Encyclopedia of American Popular Beliefs and Superstitions," is showing off the long rows of file cabinets bursting with more than a million index cards, each of which contains a different scrap of folklore or superstition. The archives were established in the 1940s by Prof. Wayland D. Hand, who hired students and research assistants to gather information from written and oral material; other universities also contributed over the years. The largest categories deal with such eternal concerns as love, death, health, luck and money. "I had someone tell me," Cattermole-Tally says, "that if you buy purple towels, your marriage will break up."

Surely, we ask, the woman didn't believe that?

Perhaps not, says Cattermole-Tally, but "she didn't buy purple towels."

Cattermole-Tally says she doesn't know whether modern-day people are more or less superstitious than our pre-industrial ancestors. "It would be hard to prove

one way or another. But considering people and the way they operate, I would say there is not much difference." She cites an example from the files, a Southern California woman who made her kids watch television from behind bales of peat moss so they wouldn't absorb any radiation.

If the woman was that worried about it, we ask, why didn't she just get rid of the TV?

"Most people don't think very logically," says Cattermole-Tally. "All you have to do is read the political pages to find that out." Most people, in fact, don't even consider themselves superstitious. "You want to know my definition of superstition?" asks Cattermole-Tally. "I have beliefs. You have superstitions." Superstition is a reflection of the way we think under stress, she explains. It's a "belief with no reality." It's not a rational process.

One way old superstitions survive through the ages is by adapting to the times. Many people, she points out, still believe that the groom shouldn't see the bride before the ceremony on their wedding day.

Why is that?

"Virgins are very powerful. You never look a goddess in the face. Actaeon looked at Diana in her bath and was torn apart by dogs. In medieval Europe, it was thought that a woman could stop a storm by raising her skirts."

She tells another story about a student who thought that if a man looked at you a certain way you could get pregnant.

What way was that?

The student didn't know. "She said, `My mother never told me,' " Cattermole-Tally says.

Over the next hour, Cattermole-Tally gives dozens of other examples of modern superstitions, including the belief that red cars get more traffic tickets and the supposed tendency of airplane crashes and entertainers' deaths to occur in threes.

Why are so many people willing to believe undocumentable things?

"I hate to say, `That's the way people think,' " she says, "but they do. People don't care what the facts are. They cling to fantastic notions. They don't want to hear what really happens." The truth is, she says, "they don't want to know."

MOST PEOPLE REGARD superstitions as quaint notions left over from the Middle Ages about black cats, broken mirrors and not walking under ladders. Psychiatrists and psychologists, on the other hand, believe that superstition arises anew in every age in response to anxiety or universal longing on the part of mankind for some kind of predictability about those aspects of life that are generally beyond human control: life, death, love and money.

"Human beings are always trying to make sense of the world," says Pitzer College anthropologist Donald Brenneis. For most people, the thought that we might live in an indifferent universe is so frightening that they prefer to blame their bad luck on something they either did or didn't do. The value of superstition is that it reduces anxiety; by making the universe predictable again, says Brenneis, it restores one's sense "of comfort and control."

ACCORDING TO former White House aide Michael K. Deaver's new book on the White House ("Behind the Scenes"), even Ronald Reagan is "incurably superstitious. If he emptied his pants pocket you would always find about five good-luck charms. I am sure he reads his horoscope every day. (Reagan is an Aquarius.)" Not only does the president not scoff at the paranormal, Deaver says, but Reagan also once told him that his dog Rex runs around the White House barking at Lincoln's ghost. A group of friends who purchased a home where the Reagans will live when they return to Southern California in January changed the address to 668 St. Cloud Road from 666 (666 being "the mark of the beast" - Satan).

A STUDY REPORTED in Psychology Today a decade ago seemed to bear out the psychologists' theory that the primary function of superstition is reducing anxiety. It found that 70 percent of college students surveyed resorted to some kind of magic - wearing lucky socks, sneakers and blouses, using lucky pens or always studying at the same library carrel. Furthermore, the study showed, the overwhelming majority of students found that using such magic usually made them feel more relaxed and less anxious.

Some of the most superstitious people of all are gamblers. Because they have so little control over the outcome of events, they often resort to random numerology: betting their odometer readings, their license-plate numbers, their children's birthdays, their wedding anniversaries. Stephen J. Conway, a 32-year-old electronics worker from Sonoma County, Calif., won $11 million two years ago in the California Lotto contest by betting the jersey numbers of such athletes as Mickey Mantle, Terry Bradshaw, Roberto Clemente and Bill Walton. Many horse-racing fans, says one local track writer, use the Holy Ghost system: If the same-numbered horse wins more than one race early on a racing card, then the fans bet that number for the rest of the day on the grounds that nature loves to complete a three (as in Father, Son and Holy Ghost.)

But superstitious as gamblers and athletes are, their beliefs are small potatoes when contrasted with those of the people who trade on the country's financial markets. One successful Los Angeles broker believes that the market always does better on days he isn't there. So when his clients' portfolios begin to drop, he leaves for a couple days. An attorney never plays the market on Monday or Friday.

Mitch Pindus, a 30-year-old stockbroker who works in Los Angeles, says he recently made a lot of money trading entirely on the basis of how a fellow broker dresses. For reasons of charity, Pindus calls the man Fred Smith. It isn't enough to say Smith is a bad dresser, Pindus says. "He is pathetically uncoordinated." He wears plaid slacks, polka-dot ties and Hush Puppies. "He has the only brown pinstripe three-piece suit I've ever seen. I used to think he was colorblind." But the crazy thing, Pindus says, is that the worse Smith dresses, the better the market does. "I'm serious," he says. The correlation is uncanny. Pindus calls it the FSCI (Fred Smith Clothing Index).

MOST SUPERSTITIOUS people instinctively rely on the conservation-of-momentum principle - if something is going right, don't change anything, including your clothes. As a result, some baseball players refuse to shave during a hitting streak or to change their shirt or pants. Former San Diego Padres pitcher John Montefusco once told the Los Angeles Times that he used to wear the same pair of underwear as long as he was winning. (If he lost, he threw it out.) Stockbrokers are notorious for this kind of thinking, says former Bear, Stearns broker Marc Shenkman. If they're sitting in front of a terminal with their feet up on the desk watching the stocks scroll by, and their stock begins to go up, they literally won't move. "They won't go to the bathroom; they'll send a secretary out for lunch; they're almost afraid to breathe. They think if they put their feet down, the stock will go down, too."

The number 13 is considered so unlucky that TWA once reported that its load factor (percentage of occupied seats) fell 5 percent on one Friday the 13th. It's a fear that goes back to primitive people, according to author Carol Potter. When they added up their fingers, they got 10; then when they added their two feet they got 12, the highest they knew how to count. Anything after that was the terrifying unknown - 13. Thirteen's reputation grew more fearsome, says Pitzer College anthropologist Brenneis, because 13 people sat down at the Last Supper, where Judas betrayed Jesus.

According to critic and film writer Michael Medved, people in the movie industry are naturally superstitious because "they know better than anyone that the notion of their becoming a star had less to do with talent than timing and luck." Los Angeles screenwriter Rowby Goren says a late friend of his would, if he happened to drop a page from his screenplay, always immediately retype it, lest this lapse somehow jinx the sale. Dick Cavett once said he touches every eighth parking meter when walking down the street. Henry Fonda reportedly used to cross his fingers when he saw a dwarf. Bette Davis once told Playboy, "If your nose itches, you'll kiss a fool."

WE REALLY are less superstitious than our ancestors in the Dark Ages, says Alan Dundes, an internationally known folklorist from the University of California, Berkeley, but that's just because science has helped replace superstition.

"This is not to say there aren't tons of examples of modern superstitions," he says. "Half these new diets are superstitions. All these beliefs connected with sports: not mentioning a no-hitter; not letting the team be with women the night before a game; professional sports people crossing themselves before shooting the foul shot. The idea that (if you're a college professor) you don't mention that you have put in a grant application for fear you won't get it. People still think if you take the umbrella, it won't rain; or if you wash your car, it will." If you think about it, says Dundes, that last superstition is really a startling conceit in personal omnipotence - the idea that what you do with your umbrella or car controls the weather for everyone.

As for advertising, he says, it couldn't function without superstition. "They have secret ingredients in gasoline and motor oil, usually with three initials - that's the magic number." One reason for the prevalence of superstition, says Dundes, is that "to some extent there has been a loss in organized religion, and people have sought alternatives: Hare Krishnas, secular humanism, harmonic convergence. Yuppies have magical beliefs in success. `Dress for success.' `Speaking of the Devil.' People are afraid the boss will appear if they just criticized him. (Such beliefs) are like Murphy's Law: `If something can go wrong, it will go wrong.' It is a way of scientifically codifying error. All I'm saying is, we can't limit superstitions to black cats crossing paths.

But the main thing to remember about superstitions, says Dundes, is that they are caused by anxiety about basic issues like love, death and health. "And when science fails - `Sorry, there's no cure for this' - that's when you go down to Mexico and get the apricot pits. The bottom line is that there will never be a time when people do not believe in superstition."