It's a free country, right? Well, not exactly. Every day, all day long, the specific position of your body and the state of your mind are under the control of a powerful and authoritative force of which you are almost entirely unaware.

It's the system of personal space. Every culture has its own, and some are so drastically different that they can cause friction -- or at least extreme unease -- when groups such as Arabs and northern Europeans get together.

Individual idiosyncracies and social context can modify the rules slightly, as we shall see. But within a culture, the code usually is firmly imprinted by age 12 and remains surprisingly constant from town to town and region to region.

For the average American, according to anthropologist Edward T. Hall, there are four distinctive spacial zones, each with a well-understood spectrum of appropriate behavior.

The nearest Hall calls the "intimate" zone, which extends outward from the skin about 18 inches. This is the range within which lovers touch and parents communicate with infants. At that distance, it is difficult to focus on another person's face, which appears larger than your entire field of vision. That is one reason why people often kiss with their eyes closed.

Within this zone, the sense of smell is important, and body heat is felt immediately. For example, sexual arousal customarily floods the abdomen with blood. Many people say they can sense the condition of a partner, even during cocktail conversation or formal ballroom dancing, by feeling the radiated heat.

The next, or "personal," zone extends from 18 inches to about 4 feet. Within this range, you discuss private or serious matters and confer with literally "close" friends. Touch is easy throughout the nearest part of this space, up to about 30 inches. Alternatively, you can keep someone "at arm's length."

(Although you may be unaware of the rules of personal space, your language is not. Many of our familiar phrases reflect our cultural code and what happens when somebody is too close for comfort.)

Within the personal zone, you can focus sharply on another person's face and read very subtle details of expression. But you'll probably move your eyes a lot to focus on various parts of the other person's face. Watch somebody else talking at this distance, and you'll see his or her gaze flick rapidly from one spot to another.

You'll also notice that personal groups larger than two or three are very rare, because it becomes difficult to maintain appropriate spacing with more people.

Casual acquaintances or people who just want to tell you something relatively unimportant had better stay well outside the 30-inch inner personal zone. If they don't, they'll make you very uncomfortable, and you may find yourself inadvertently backing up until you're trapped against a wall.

One reason that economy-class air travel frequently is so ghastly is that the strangers who are your seatmates are way inside the close personal zone. Worse yet, side-by-side seating is widely felt to be the most intimate arrangement. Men will not voluntarily choose it unless the alternative is sitting too far apart to talk.

In one study, American, English, Dutch, Swedish and Pakistani subjects all ranked side-by-side positions as psychologically closest, followed by corner seating, face-to-face and various diagonal arrangements.

The "social-consultive" zone, in which most day-to-day work and ordinary conversation occurs, starts at 4 feet and goes to about 10 feet. In American culture, eight feet is the point at which you pretty much have to acknowledge another person's presence. Beyond that, you can ignore someone without giving obvious offense.

Usually, there are no smell or heat sensations at 4 to 10 feet, and much nonverbal information is conveyed by large-scale body language. The whole body is visible as a unit at about seven feet, although you can only focus on part because the clearest vision occurs in a cone of about 15 degrees from the eyeball.

Finally, there is an all-purpose "public" zone that begins at about 10 feet and extends to 25 feet. Thirty feet is the customary nearest distance for addresses by public officials or celebrities.

Studies have shown that people are more likely to interact with somebody who looks weird if that person stays well outside the personal zone. In one experiment, a researcher dressed as a punk rocker pretended to be looking for help from people sitting at tables in a shopping mall food court.

"Although only one in 15 people consented to help the punker when she sat right next to them, and 40 percent agreed to help when she sat at a medium distance," the researchers found. But "80 percent of the people agreed to help her when she took the seat farthest away."

Over the Line

When someone does something that violates the tacit rules of the zone system, we are perplexed, annoyed or both. For example, if a person wanted a date with you and asked you out from 10 feet away -- two feet beyond the farthest range of business conversation -- you'd certainly think twice about agreeing, even if you were initially inclined to go.

On the other hand, a Latin American or French person, from a culture with a much closer personal interaction distance, could seem to be too "forward" or "coming on too strong" if he or she made the same request from two feet away.

Sometimes, the resulting discomfort is intentional. Psychologist Robert Sommer notes in his book Personal Space that police interrogators are taught to intrude well inside the personal zone when questioning suspects.

Similarly, we often decide that someone is wearing "too much" perfume or cologne if the scent extends past the distance of personal space. So if you can smell a woman's perfume 8 feet away, you may find it irritating -- not just because of the odor itself but because she is making what should be an intimate olfactory statement in public space.

Another reason is that Americans work hard to suppress smells and don't use them much for social cues. Hence, the enormous volume of our deodorant, mouthwash and breath-mint industry.

Many Arabs, by contrast, have a narrower personal zone, often breathe on close acquaintances while talking and depend more heavily on scent. That doesn't mean that their cultures are any less fastidious about personal hygiene. Rather, "by stressing olfaction, Arabs do not try to eliminate all the body's odors" within the personal zone, Hall writes in his book The Hidden Dimension, but "use them in building human relationships" and to "keep tabs on changes in emotion."

Size Does Matter

Variations abound. In much of India, there are only two zones: intimate and public. Some Mediterranean cultures have personal zones that begin much closer than those typical of Americans or northern Europeans. That's why Americans sometimes feel crowded or stressed in France or Italy.

And, of course, some cultures simply build things differently. Japanese rooms seem too small by Western standards, and the furniture tends to be placed in the center rather than along the walls. What we don't know is that the traditional Japanese room configuration can be changed by moving the lightweight walls.

Thus, what we perceive as a permanent space is merely a temporary arrangement from another perspective. Conversely, our fondness for big spaces with furniture at the edges can make Western rooms look barren to the Japanese eye.

In 1967, Hong Kong's housing authority was constructing apartments with 35 square feet per occupant. That's 5-by-7, about the size of a modern work "cubicle." When a westerner asked why the design was so stingy, a construction supervisor replied, "With 60 square feet per person, the tenants would sublet."

Birth and Turf

But each culture's rules arise from the same fundamental biological impetus, which extends throughout the animal kingdom -- the tendency to mark and defend one's own territory or to avoid intruding on someone else's.

Think about that next time you sit down in a cafeteria or library. If you find an empty table that can seat six or eight, you're probably going to sit at one of the corner chairs -- an "avoidance" position, according to psychologists -- and you'll most likely face the door because some ancestral instinct says you might have to flee.

Dogs mark their territory by urinating at the boundaries. Happily, human civilization has not evolved this trait. But we're constantly doing the equivalent.

Everyone has been vaguely irritated by the person in a movie theater who spreads coats and bags across six seats and then goes off for popcorn. Nonetheless, we'll bypass any space that faintly appears to be "marked" by an absentee squatter. One study showed that, even in a busy and crowded library, a simple stack of magazines in front of a chair kept that seat open for more than an hour.

Analogously, you may find that when you enter someone's home, you carefully avoid sitting in what seems to be the father's "personal" chair. Or you may notice how some passengers in the Metro system claim two spaces -- an "aggressive" position -- by putting a briefcase next to them or taking the outermost of the two side-by-side seats.

Special Effects

Powerful as personal-space rules are, they can vary a great deal with context. For example, both schoolchildren and adults tend to sit closer together as room size increases. On the other hand, the presence of loud noises -- and thus, ostensibly, the level of personal stress -- tends to increase the size of space zones for men, though not for women.

"A possible explanation," two psychologists write, "is that socialization may lead women to share their distress with others, whereas similar norms prohibit men from behaving in ways indicative of sharing distress."

Context apparently can alter the standard American crowd configuration, which allows about six to eight square feet per person. One theater owner told a reporter that, when he was showing a typical family movie, patrons awaiting the next show would stand so far apart that the lobby would hold no more than 100 or 150 people. But when the theater was showing a sexy comedy, he said, "we can get 300 or 350 in the same space."

Even commercial transactions can be affected. "For example, purchasing something in a store in cultures of the north European tradition is generally considered a private matter which excludes strangers," Hall writes. "In the Mediterranean countries, particularly as one approaches the Arab world, the context changes and the purchasing of virtually anything is a public matter in which strangers participate in ways that would only be classed as personal and intimate by northern Europeans."

In addition, mental health status may be important. In general, people with personality abnormalities require more personal space. Studies have shown that prisoners who committed violent crimes against people have much greater space needs than those whose crimes were theft or drug use. In addition, prisoners with the largest space requirements usually had more prior arrests.

Eyes Right

Space can be invaded by vision as well as another's presence, and visual territories also differ from culture to culture. Unlike, say, the French, whose "frank" stares can be intimidating to outsiders, Americans rarely look directly at each other for very long, even during intense conversation.

In the animal kingdom, an averted gaze often indicates a passive stance. But in America, it is merely polite. We consider it an invasion of personal space to "stare" at someone, even briefly, and sensitivity varies by distance.

Thus, when the door closes on a crowded elevator, you'll usually notice two behaviors. First, the occupants automatically adjust their positions to create the same amount of space between each. Then most people either look down at their feet or up at the floor indicator rather than at one another.

In fact, one experiment showed that people will sit closer to a picture of a person with the eyes closed than to an otherwise identical image with the eyes open.

The English, on the other hand, regard it as rude not to look directly at the other person during conversation. To do otherwise makes it appear that you're not paying attention.

But in order to hold the head still and the gaze steady while listening to someone, one has to be far enough away so the eyes aren't constantly shifting around the other person's face. Thus the English tend to stand near the outer limits of American personal space, making them seem aloof, reserved or literally "stand-offish."

Taking a Stand

There are even substantial cultural differences in positions that people assume while talking. Hall and his colleagues paid careful attention to the way various American ethnic groups typically stand.

Almost none place themselves face to face. In this country, it is taboo to breathe on another person during speech unless the circumstances are quite intimate.

Middle-class whites tend to arrange themselves so the line of their shoulders forms an acute angle. Working-class blacks, however, tend to face somewhat farther apart, forming a right angle. In fact, the closer they stand to each other, the less they face each other. Latinos are most likely to make an obtuse angle. Blacks and Latinos are more likely to employ peripheral, rather than direct, vision.

Nonetheless, even though whites face each other more directly than either of the other groups, they have minimal body contact and stand at least a forearm's distance apart. Blacks tend to stand closer and have considerably more contact. Latinos are somewhere in between.

A Touch of Culture

On the broad cultural scale from "non-contact" cultures such as the extreme northern European to the touchy-feely societies of the Mediterranean, Americans are at the low end. A classic survey from the 1960s looked at pairs of people in coffee shops worldwide. Touch rates averaged 180 times an hour in San Juan and 110 per hour in Paris, compared with two per hour in Gainesville and zero in London.

In the realm of touch, sex definitely matters. When investigators looked at how Connecticut hospital patients responded to touch by nurses before surgery, the vast majority of women reacted positively. The same actions, however, made men very nervous.

As a rule, waitresses increase the amount of tips by touching diners briefly. But it doesn't work for waiters.

Interestingly, the right to touch usually increases as you move up the social hierarchy -- that is, the highest-ranking person may touch a subordinate but not the other way around.

In fact, you can fairly easily determine the relative social status of people by watching who touches whom. The obvious exception is in cases where touching a highly celebrated person, such as the pope or an American president, seems to confer some sort of benefit.

Moreover, there are wide cultural variations in the amount and kind of touching considered tolerable. In the United States, African Americans of both sexes are more prone to touch than whites.

But Americans of any race are far more likely to touch persons of the opposite sex than are people from Mediterranean or Far Eastern cultures. We're also pretty demonstrative in same-sex touch.

When male and female students from the United States, Spain, Chile and Malaysia were surveyed, females were much more likely to feel positive about same-sex touching than males in all cultures. Malaysians were the most negative, followed by Chileans, Spanish and Americans of both sexes.

When the researchers asked how the subjects felt about two statements -- "I am comfortable putting my arm around the shoulders of persons of my sex" and "I sometimes like some persons of the same sex putting an arm around my shoulders" -- they found that "only U.S. men and women and Spanish women tended to agree, but all other groups tended to disagree."

Sex and the Single Bench

Sex is not always a key variable in managing personal space. When a male or female has occupied the end of a 12-foot bench, the next arriving person will take a seat at the opposite end, no matter the sex of the incumbent. But in a bar, a man who strikes up a conversation with a woman two stools away will almost always move to close the gap. Two men who begin talking will leave an empty stool between them.

Numerous researchers have found that "females have smaller personal-space zones than men and that, in general, heterosexual pairs have smaller zones than same-sexed pairs."

Racial differences also are significant, at least in the United States. One survey notes that "when blacks and whites interacted, their personal space requirements were greater than when members of the same race, black or white, interacted" and that "pairs of Chicanos stand closer together than whites, who in turn stand closer than blacks."

Office Affairs

Office space and access to privacy are customarily allotted according to rank, even when the practice is illogical or counterproductive. For example, social workers or admitting nurses in hospitals may really need private offices to interview clients. But often the only private offices belong to the supervisor, who never conducts interviews.

One reason for the perpetuation of this system is that it keeps bosses in control of contact. In general, the bigger room and larger desk given to superiors are not required for their work. Instead, they are a way of limiting the kinds of behavior that can be performed in that space. The long desktop between you and your superior keeps you from breeching personal distance and thus establishing a less formal relationship.

Use of private office space varies dramatically from culture to culture, however. In Britain, where accent and social class confer status, office size and privacy are far less important. Typically, Germans and many Swiss keep their office doors closed while they work. Getting inside requires a formal knock and permission to enter.

Americans, on the other hand, almost always keep their office doors open. Closing your room without an obvious need for privacy is considered peculiar, if not outright antisocial.

Nonetheless, American workers almost never barge into even the most invitingly open office. Before entering, we either knock on something, clear our throats or lean inside -- with hands on the door frame and feet carefully planted outside the entrance.

Border Wares

Thanks to Robert Frost, many Americans believe that good fences make good neighbors. And with good reason.

"That we are terribly territorial is reflected by the fences we erect," says anthropologist David B. Givens, director of The Center for Nonverbal Studies in Spokane. "The meaning of a fence is the barrier it provides, and according to the American Fencing Association, 38,880 miles of chain link, 31,680 miles of wooden and 1,440 miles of ornamental fencing are bought annually in the United States alone. That's nearly enough to circle the Earth three times."

But in many ways, we're much less boundary-conscious than many other cultures. In Britain, it is rare to see even closely spaced townhouses not clearly separated by fences or even walls. In Latin America, the design of even small houses includes a walled courtyard.

In the United States, where there are frequently no visible divisions between lawns in the suburbs or front yards in a row of townhouses, erecting a fence can be viewed as a hostile act. Unlike in many European cultures, neighbors in America are automatically assumed to be friendly.

It is considered normal that your children play with those next door, and neighbors have certain unspoken rights to borrow certain kinds of things or ask for various favors. The same relationship would be quite abnormal in France or Britain, where simply living next to someone does not create some kind of bond.

Nor does it seem to be the case in U.S. nursing homes or dormitories. In both settings, people tend to have fewer disputes and to be more friendly with those who lived at least one or two doors away. Familiarity actually does breed contempt.