Andrei Gromyko told them to John F. Kennedy during the Cuban missile crisis. Adolf Hitler successfully passed them off on Neville Chamberlain just before World War II. And more recently, accused spy ring leader John Anthony Walker Jr. allegedly fooled the Navy about his espionage activities for almost two decades.

"Lying well is a special talent, not easily acquired," says University of California at San Francisco psychologist Paul Ekman, who has studied lying for 20 years.

To lie successfully, Ekman says, "one must be a natural performer, winning and charming in manner. Such people are able, without thought, to manage their expressions, giving off just the impression they seek to convey."

Lying, falsehoods and deception "provide a unique window to voluntary and involuntary behavior," says Ekman, author of a new book called "Telling Lies: Clues to Deceit in Marketplace, Politics and Marriage." "In terms of understanding brain-behavior relationships and emotion, lying provides an excellent situation."

Ekman's studies of numerous people engaged in telling lies and the truth have demonstrated that a lie often can be betrayed by changes in voice, facial expressions, use of words and body movement.

By analyzing videotapes, frame by frame, Ekman found what he labels "leakage" -- clues that lying is taking place. His work, which has been supported by the National Institute of Mental Health, is being used to train other people to detect lying -- ranging from psychologists to people concerned with national security.

His studies also suggest just how hard it can be to detect particularly good liars -- especially with the standard polygraph (lie detector) test which is used about one million times a year by private companies, police departments and federal agencies including the military and the Central Intelligence Agency.

Most recently, the on-going investigation of accused spy John Anthony Walker Jr. highlights how important detecting lies and breeches in national security can be, Ekman says.

Both Walker, a retired Navy communications officer, and his brother Arthur James Walker, also now under arrest for spying, had "top secret" clearances in the Navy. While the Navy refuses to divulge whether or not the Walkers had a polygraph test, earlier this year, Rear Admiral John L. Butts, chief of Naval Intelligence, submitted a statement to the Senate Governmental Affairs Subcommittee on Investigations saying that it is Navy policy to use the polygraph for such security screening.

"The polygraph is a valuable and effective tool for specific personnel security purposes," Butts wrote. "The polygraph is particularly useful in assessing candidates for access to our most sensitive information and for periodic reassessment of such individuals."

Polygraph tests use electrodes -- usually four -- to keep track of changes in the autonomic nervous system, which regulates a wide range of bodily functions from breathing and heart rate to skin temperature. These changes signal alterations in emotions, but can't measure directly if someone is lying. For this reason, controversy rages over the accuracy of polygraph tests.

While more than 4,000 articles and books have been published on the reliability of the polygraph test, Ekman notes that "less than 400 actually involved research, and of these no more than 30 to 40 meet minimum scientific standards."

Critics also contend that polygraph tests can be fooled by physical activities like biting one's tongue, the use of drugs, hypnosis and biofeedback. These countermeasures are used when someone is first hooked up to get a baseline reading on the polygraph. Then later, when the person lies, the test may not pick up the deception.

"The Soviets have a school to train agents how to pass polygraph tests," Ekman says. "And in addition to the Soviet school, there is an American school that travels around the country claiming to teach people how to beat polygraphs.

"We need to know: Does that training work and can we detect if someone is using that training. I think it is a near scandal that this country has not done the work to explore how effective countermeasures can be and if we can counter the countermeasures."

Ekman notes in "Telling Lies," how former acting assistant secretary of defense for health affairs, Dr. John Beary III, ". . . warned the Pentagon that its reliance on the polygraph was endangering rather than protecting national security."

Even without training, some people may be able "to beat the polygraph," Ekman says. "If we could identify such people ahead of time, then we better not rely on a polygraph, we better rely on the more expensive field (or background) examinations."

Just as some people learn naturally how to tell lies, recent work at Ekman's lab also shows that other people apparently can teach themselves to spot a liar.

Most people -- including mental health professionals accustomed to detecting lies in their practices -- perceive lies correctly only about 50 to 60 percent of the time. (With several weeks of training, Ekman says he can teach people how to raise their lie detection accuracy rate to about 90 percent.)

But when Ekman tested several Secret Service agents' ability to detect lying, he found intriguing results. One agent with 10 years of experience with the Secret Service scored the usual 50 to 60 percent accuracy rate. But two other agents, each with more than 20 years of experience, scored almost perfect results.

"These findings suggest that people who have had a lot of experience -- 20 years or more -- already know what we have learned in the laboratory about detecting lies," Ekman says. "But they have picked it up in the school of hard knocks."

Liars can also fall victim to their deceit by believing in their own lies. Witness former Italian prime minister Benito Mussolini who in 1938 reduced the composition of an Italian army division from three regiments to two because it enabled him, Ekman explains, "to say that fascism had sixty divisions instead of barely half as many.

"Because he forgot what he had done several years later, he tragically miscalculated the true strength of his forces. It seems to have deceived few other people except himself."

A more recent lie gained prominent media attention when Cathleen Crowell Webb said she had lied about being raped several years earlier by Gary Dotson. Dotson was convicted and served six years in jail based on Webb's original courtroom testimony.

"The real lesson of the Cathy Webb situation is that if we believe her now, it means that she is the kind of person who, without any special training, is capable of deliberately lying, fooling lawyers, judges and juries," Ekman says. "What it really shows us is our vulnerablity to lies. She's not Lawrence Olivier, she's not a trained Soviet agent. Whether she's lying or telling the truth, that's the nature of human life, you can't always tell. There's no way to be absolutely certain of the truth."

The second cost of lying for Webb is this, Ekman says: "If we believe her now, it's saying that we can never really believe her. Once you have been a liar and have been caught or confessed, can anyone ever trust you again? That's the main reason that we try to teach our children not to lie. Once someone has lied, it's very hard to trust someone again."