In the animal kingdom, males exhibit what is known as "display behavior" in order to attract females and to ward off rival males. They thrust out their chests, ruffle their plumage, and generally try to appear more impressive than they really are. On nature shows, this is comic. It appears comic, too, when it shows up among humans: the guy in the Camaro with all the gold chains, say, or Vanilla Ice's haircut. It has been discovered that display behavior is much more common among humans than had been previously believed.

Have you ever wondered why:

• Men who have never been west of Kentucky can tell you about the mentality of the Japanese?
• Men who can't pay their credit-card bills have a plan for dealing with the national debt?
• Men who aren't on speaking terms with their families know how to achieve peace in the Middle East?
• Men who flunked high-school physics can explain what went wrong at NASA?
• Men who haven't had a date in six months know what women really want?

Try an experiment: Ask my friend Jeff, who spends his weekends fixing up his Harley and watching female mud wrestling, how he thinks political autonomy will affect the economies of the Baltic states.

His brow will furrow; he will purse his lips thoughtfully. "It's interesting that you mention that...," he will begin, and then he will come up with something-probably nothing remotely feasible, but something.

This behavior-the chronic answering of questions regardless of actual knowledge is known as Male Answer Syndrome. The compulsion to answer varies from person to person, but few men are happy saying, "I don't know." They prefer, "That's not what's important here."

They try not to get bogged down by petty considerations, such as, "Do I know anything about this subject?" or "Is what I have to say interesting?" They take a broad view of questions, treating them less as requests for specific pieces of information than as invitations to expand on some theories, air a few prejudices, and tell a couple of jokes. Some men seem to regard life as a talk show on which they are the star guest. If you ask, "What is the capital of Peru?" they hear, "So tell us a bit about your early years, Bob."

Sometimes this expansiveness is appealing. If you ask a woman, "Why did Madonna go on the David Letterman Show?" she will simply shrug helplessly, acknowledging that some things are simply unknowable. A man, on the other hand, will come up with a few theories (she has the same agent? overdose of Prozac). Men have the courage and inventiveness to try to explain the inexplicable.

But Male Answer Syndrome (MAS) is by no means harmless, as my friend Pauline discovered at the age of 8. She had found that eating ice cream made her teeth hurt and asked her father whether Eskimos had the same problem. "No," he said. "They have rubber teeth." Pauline repeated this information in a geography lesson and found herself the laughing stock of the class. That was how she learned that a man, even if he is your own father, would rather make up an answer than admit to his ignorance.

Later in life women run into the same problem: Men can speak with such conviction that women may be fooled into thinking that they actually know what they're talking about.

My friend Jeff (he of the Harley) is full of expertise on subjects as diverse as global warming and Elvis' current whereabouts. In reality, however, he is an expert at only one thing: making very little knowledge go a very long way. For him answering is a game, and not knowing what he's talking about just adds to the thrill.

Expressing skepticism can be highly inflammatory. Even mild-mannered Abe Lincoln types may react to, "Are you sure about that?" as a vicious slur on their manhood and find themselves backing up a ludicrous assertion with spurious facts.

Many women actively encourage male answering behavior. There is in the female correlative condition known as the Say What? Complex. Women who behind closed doors expound eloquently on particle physics may be found, in male company, gaping at the news that the earth is round.

MAS tends to be mild until puberty; boys begin to speak with authority on matters of foreign policy at the same time they start to grow facial hair. And how MAS developed: Since killing wooly mammoths and attacking enemies with rocks are now frowned upon, and since shirts open to the navel are not appropriate in every social situation, men prove their masculinity by concocting elaborate theories about football.

Growing awareness of MAS has led some to call for a moratorium on all male-female conversation. This is alarmist. But care should be taken. Women must remind themselves that if a man tells them something particularly interesting there is a good chance that it is particularly untrue.