David Thomas, a crackerjack car salesman, can spot them as they come through the door. They're hesitant. Their guard is up. They want to keep their distance.

He will extend his hand for a friendly handshake. Make eye contact. Later he will run his hand over the leather upholstery or the burled-wood steering wheel. Chances are, they will do the same.

Pretty soon they'll be in Thomas's office. If they lean back in the chair, away from him, he's got more work to do. But if they lean forward, he knows in a few minutes they'll be huddled with him over a contract.

Thomas, who used to sell more Lexus automobiles than almost anyone else and now runs his own dealership in Dallas, is a student of proxemics, though he wouldn't call it that. To Thomas, it's just old-fashioned psychology. He knows how human beings use their bodies and the space around them to send and receive messages.

It's like a dance that we do: A stranger steps into our elevator and we move to the corner. We're on our cell phone, gesturing and grinning as though the person we're talking to is just feet away instead of miles. We step out of the room for a moment, return and find that our chair is taken. So we hover nearby.

"There's so much you can glean from observing the distances between people when they interact," says William Pulte, anthropologist, linguist and associate professor in Southern Methodist University's education department.

Proxemics, the study of how people perceive and use the space around them, was founded in the 1950s by anthropologist Edward T. Hall and popularized in several of his books, including "The Silent Language" (1959) and "The Hidden Dimension" (1966). Hall observed that humans like to keep their distances from one another and that those distances vary according to social interactions.

Intimate interactions such as wrestling, whispering and embracing take place within about 18 inches. Personal interactions such as conversations between husband and wife take place from 1.5 to four feet. Salesclerks and their customers, business associates and strangers stay four to 12 feet apart. Beyond that is the outer circle, the realm for speechmaking and other public activities.

"I think these degrees of separation, these categories, are universal," Pulte says. "What varies from society to society is the actual distance."

For example, conducting business deals at a distance of four to 12 feet is typical for middle-class Anglo-Americans, he says. "But in Buenos Aires or Mexico City, it's more like three to six feet." In general, people from Latin America, much of the Mediterranean world and the Near East are comfortable at closer distances than most Americans. Asians, on the other hand, prefer greater distances.

This leads to stereotypes, says Pulte. "An American goes into a department store in Mexico City and another person positions himself 31/2 feet away. And he thinks, 'Oh, these Mexicans are so pushy.'

"In Germany, it might be four to eight feet. We think, 'Hey, these Germans are so unfriendly. They don't like us much.' "

The result is culture shock, says David B. Givens, director of the Center for Nonverbal Studies in Spokane, Wash.

"We take these things for granted, build up our expectations about what our nonverbal communications mean. We think: That's reality. Until we go to Italy or South Africa, or some tribal area."

Givens says experts have estimated that anywhere from 62 percent to 99 percent of all human communication is nonverbal. "That includes facial expressions, gestures, postures, fashion."

Distance communicates, Givens says, because we are territorial creatures. Much of our nonverbal communication is about dominance and submission: Who gets the bigger office. Who gets to sit at the head of the conference table. Think of the Marine drill sergeant nose-to-nose with the trembling recruit. Givens says that if you stare at a silverback gorilla and he looks back, you'd better look away. Because if you don't, he'll soon be in your face.

We primates guard our territories, large or small.

Jill Bremer, an image and communications consultant in the Chicago area, teaches proxemics along with other communication skills such as public speaking and correct dress. Bremer, who has a degree in musical theater, says her awareness comes out of her years onstage, where body language is vital.

"A lot of times we're confused about these things," she says. "Why are you so far from me? Why do you move away when I move forward?

"The biggest problem most people have is overfamiliarity," she says. "I blame much of it on business casual dress, because it encourages us to be overly familiar with people. As an offshoot, we invade each other's work space, fiddle with the things on each other's desks."

In her classes she emphasizes cubicle etiquette. "How can we get along when there are no doors to knock on?"

Violations of work-space etiquette include "prairie-dogging" -- popping up over cubicle partitions to start, or barge in on, conversations -- and lingering in doorways.

Other transgressions, she says, involve touching. "Generally, save touching for your personal life. The only acceptable touching in business is the handshake."

All this, Pulte says, is part of a nonverbal communication spectrum that also includes tactilics (the language of touch) and oculesics (the language of glances and stares).

"Among Eastern European Jewish people, you will see two men standing and talking, and they will poke each other in the stomach for emphasis. It looks funny to most Americans. But it all converges because if you're in a culture where they stand closer, there tends to be a lot more touching."

When women in Atlanta walk past someone, typically they glance up and smile briefly. Women in Boston, on the other hand, may glance but they do not smile. The difference, no doubt, has given rise to many a misunderstanding.

"It's not intended to be flirting," Pulte says of the Southern women. "Just to be nice and polite."

With all its tribal and regional variations, body language goes back at least a million years, he says. "Then about 100,000 years ago, verbal language emerged. But human beings did not drop body language. Since then people continue to communicate in both channels."

The acceleration of time and technology has added new channels. "About 100 years ago, with the development of the telephone, for the first time we find conversations taking place without body language," Pulte says. E-mail and online chatter further distance us from face-to-face contact. Now we communicate with dozens of people a day without being able to read their body language, or to send our own.

Will we lose the old facility of reading each other's distances, glances and gestures?

Pulte doesn't think so. "Body language is so deeply rooted in human nature that it's not endangered," he says, though some people are so absorbed in electronic messages that they may become less astute in judging the nonverbal kind.

But even if there's nobody to receive them, we still send them.

One of Pulte's students observed people talking on their cell phones. He reported that about 20 percent of them still gesture and smile and nod as though somebody else were actually there listening and watching.

Old behaviors from a million years of evolution and conditioning die hard, he says. "I don't think this will go away."

"I teach our salespeople that it all starts at meeting and greeting the clients," Dave Thomas says. "They have their hesitation built up for good reason. So eye contact is crucial. A firm handshake is crucial. We treat them as a guest in our home. If they ask where the restroom is, don't point. Extend your hands and show the way.

"Remember the old TV show, 'The Price Is Right?' The game show models that presented the toaster would run their hands over it as though it were a $50,000 car. We adjust the seat and adjust the seat belt. If you want them to touch the wood of the steering wheel, this nice burled wood, you touch it, too. It even goes to the way you shut the door. It's like selling a suit: The salesperson holds up the suit, helps you put your arms into it.

"If you haven't done a good job in building rapport, you can see them lean back in the chair, lean away from you. If you've made a connection, they'll lean forward. You've just got to mirror them. If they want to get close, or if they step back that's when you step back."