BUENOS AIRES — The problem with Guille is that he's a close talker. It's not like he has nasty breath or smells bad, but he gets in your face, even as you keep inching back. Leandro is the opposite: You try to move closer to talk to him, and he steps away. As you feel the need to approach a bit more, he again retreats, like in some kind of ritual dance.

A while back, I realized the reason for this is that each of us has our own idea of what represents an ideal distance with people, a bubble that feels neither too crowded nor too distant. Guille's bubble is clearly much smaller than mine, and Leandro's much bigger.

In 1966, anthropologist Edward T. Hall was the first to discuss this subjective frontier, or "personal reaction bubble," which influences our behavior. His book The Hidden Dimension describes four types of space: intimate space (about 46 centimeters around us), which is normally reserved for lovers, children, close relatives, friends and pets; personal space (from 46 to 120 centimeters), used in conversations with friends, colleagues or at gatherings of people you know; social space (120 to 240 centimeters), meant for strangers, new acquaintances or members of recently formed groups; and public space (more than 240 centimeters), used for large gatherings, public speaking, seminars or the theater.

Clearly Guille's personal space is less than 46 centimeters, which is why he's always entering mine, and Leandro's is bigger, which is why his body language always suggests that I'm encroaching on his! Hall was very clear on this: Personal space draws out our comfort zone and psychological security, but it's very difficult to measure. It changes according to personal experiences, culture, the time we live in, age groups and social classes. In the West, for example, Hall's studies found that the average person's personal space extends 60 centimeters from each side of the body, 70 centimeters to the front and 40 behind. But in Latin cultures, it's smaller. Anglo-Saxons seem to require the most.

There are also social differences. Rich people expect to have larger personal space than the poor, who tend to live closer together. In large cities such as Buenos Aires, personal space tends to be smaller than in the countryside.

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In some situations, people make exceptions about their personal space because life demands it: taking the subway, getting into the elevator, going to a concert or taking part in protests all require sacrificing personal space a bit. In these cases, people respond differently: they accept the discomfort more graciously, for example, if it's for fun or just for a short while. With public transport, it's different.

Psychologist Robert Sommer says people tolerate crowds on subways, buses and elevators by dehumanizing those next to them. That is, they regard them almost as objects instead of people invading their intimate space. Which explains why people tend not to make eye contact and look so lifeless on the subway.

The point is, distance influences our behavior and should, therefore, be considered when it comes to designing and furbishing buildings. Experiments on human communication have shown, for example, that people prefer to face each other when talking, rather than sitting next to each other. Obviously, you might say, so they can see each other's faces. Yet those studies also show that as personal distance increases, they prefer to sit beside one another, even in the best acoustic conditions. That is, we tend to keep ourselves inside our personal space.

Another finding is that the size of a room determines conversational distance. In smaller rooms, people tend to move closer, rather like my friend Guille.