Eventually, Chance hopes to see something else: a day when a device like his replaces the old, often inaccurate polygraph as the best way for the U.S. government to detect lies told by spies, saboteurs and terrorists.

Chance is among dozens of university and government researchers who have invigorated the hunt for a better lie detector, an effort that has been made more urgent by America's focus on national security since the terrorist attacks of Sept. 11, 2001.

In labs across the nation, researchers are using technologies originally developed to examine diseases, brain activity, obesity and even learning disorders to try to solve some of the mysteries of human conduct. The provocative idea behind some of the research is to go beyond measuring the anxiety of a liar — as polygraphs try to do — and to catch the lies as they form in the human brain.

"We need something; we have a country under stress" because of increased fears of terrorism, says Chance, 90, a biochemist and engineer who helped to develop military radar during World War II. "It might be fixed by finding out what people are thinking about."

Even its staunchest defenders doubt that the polygraph is up to the job. Invented in 1915, the device uses wires, cuffs and a chest harness to measure changes in breathing, perspiration and heart rate. The presumption behind polygraph tests is that such changes can be brought on by the stress of telling a lie.

But researchers have long questioned the polygraph's accuracy, in part because the test itself can make a person nervous enough to skew the results. In criminal cases, the accuracy of such tests can vary widely. Courts in only one state, New Mexico, routinely accept polygraph results as evidence.

And security screeners who use the machine to try to pick out would-be terrorists or spies have a more difficult challenge, polygraph critics say. Without details of a specific crime or security violation to ask about, polygraphs miss real spies and sometimes implicate innocent people.

Former CIA officer Aldrich Ames, who spied for the Soviet Union, and former Defense Intelligence Agency analyst Ana Belen Montes, who spied for Cuba, both passed polygraphs.

The polygraph is "a technology under duress," says Frank Horvath, a Michigan State University professor of criminology and a Defense Department adviser. "The question is: Is there some way better, and how do you find it?"

The Defense Department, the FBI and the CIA are among the U.S. agencies trying to answer that.

Still no proven way

The Defense Department's Polygraph Institute at Fort Jackson, S.C., is financing at least 20 projects aimed at finding a better lie detector. Another Pentagon office, the Defense Advanced Research Projects Agency, is exploring magnetic resonance imaging (MRI) and other technologies. The FBI and CIA are backing more research.

Because much of the work is secret, it is difficult to estimate how much is being spent.

All the projects are in their early stages, and they are shadowed by a glaring fact: Scientists still haven't proven that there is a scientific way to catch a liar. If a device such as Chance's were to become the standard, a range of ethical and legal questions would pop up over how it should be used.

For now, government examiners continue to rely on the old device.

The Polygraph Institute's most recent annual report says it gave 11,566 polygraph tests in fiscal 2002 for the Defense Department and other U.S. agencies, slightly more than the average number for the past five years.

About three-quarters of those were security screenings aimed at weeding out potential spies and terrorists. All but 20 test-takers were cleared; as of September 2002, the last time the institute issued a report, those people were being investigated.

The institute's tests do not include hundreds, perhaps thousands, of tests done on FBI, CIA and National Security Agency employees and applicants by examiners within those agencies. Those numbers are classified.

Developing an alternative to the polygraph "isn't going to be solved in the short term," says Stephen Fienberg, a psychology professor at Carnegie Mellon University in Pittsburgh who led a federal study last year that was critical of the polygraph. But "some of these things are intriguing."

The 'trauma of deceit'

Before 9/11, Chance's lab was using high school students to study how the brain responds to stress, including what Chance calls the "trauma of deceit."

His chief tool was the "cognoscope," near-infrared light sensors mounted on a Velcro headband that measured blood and oxygen flow in students' brains when they were asked to lie.

Chance found that forming a lie produced a milliseconds-long burst of bloodstream activity in the prefrontal cortex, the part of the brain known as the center of decision-making.

"You could see the thought before it is articulated," he says.

After 9/11, the Defense Department became interested in Chance's work.

At the Polygraph Institute last year, 42 soldier volunteers tested the cognoscope by answering questions about a staged crime. Some were truthful; others were told to lie about their involvement. The device correctly picked the liars but also recorded what polygraph examiners call a "false positive" — a soldier who was telling the truth but whose infrared brain image indicated he was lying. Chance hopes further research will show why.

If proved effective, the cognoscope would have advantages over the polygraph. Polygraph results require interpretation; the cognoscope gives an instant answer.

Can 'intent' be detected?

Chance is testing larger numbers of students. His goal: to understand how "differences between individuals" could affect the cognoscope's ability to detect deception. He wants to explore whether the technology could detect not only deception, but also thoughts with "malevolent intent."

"The more we can learn about what's in the other guy's mind," he says, "the better off we'll be."

Chance acknowledges that he's troubled by the ethical questions raised by a device that might be able to observe people's thoughts before they realize they have had them.

He sought advice from Arthur Caplan, an ethicist who also is a Penn professor. Caplan's verdict: Mind-screening would be OK at airports and in government job interviews, situations in which those tested would be presumed to have waived some privacy rights.

And beyond that?

"It's the great unknown," Chance says, "or at least one part of it."

In another lab at Penn, Daniel Langleben is using an MRI machine to try to detect deception in a different area of the brain. His work is privately funded, but the Polygraph Institute has approached him about sharing his findings.

Based on his studies of addicts and learning-impaired children, Langleben theorized that telling a lie requires two brain actions: suppressing the truth, then concocting a falsehood. Finding evidence of those tasks would be the sign of a deceptive brain, he thought.

In 2001, Langleben issued playing cards to 22 student volunteers and told them to lie about which card they held. A scanner that places the body in a magnetic field and measures tiny changes in the brain's blood flow was aimed at areas of the brain's cortex that are linked to thought suppression.

Langleben found that the areas that "lit up" during truth-telling also were activated by lies. But other areas of the brain were particularly active when subjects lied, which he says validated his theory.

Langleben thinks the MRI has an advantage over the polygraph because it charts the lie, not the anxiety that might be caused by lying. But the drawbacks are clear. MRI tests cost up to $1,500, three times more than most polygraphs. MRI machines also are unwieldy and require a willing participant. Slight movements by a test subject can nullify the results.

"We think we're on to something," Langleben says, "but we're still working out exactly what."

Linking heat and deception

In Rochester, Minn., in 2001, endocrinologist James Levine was performing obesity research by using a thermal-imaging camera that observes how much heat is thrown off when a person chews.

Suddenly, a large screen accidentally fell to the laboratory floor. Levine's startled test subject yelled. Levine nearly did too when he saw what the camera had recorded. White patches, indicating unusual amounts of heat, suddenly had appeared around the camera's image of the subject's eyes.

"We thought, 'Is this associated with other forms of stress, such as deception?' " Levine recalls.

The Polygraph Institute was intrigued. It tested thermal imaging on 20 soldiers at Fort Jackson. Levine's camera identified six of the eight who lied about taking part in a staged crime, and 11 of the 12 who told the truth. One truth-teller was wrongly deemed a liar.

Thermal imaging has several potential advantages. Unlike polygraphs, thermal imaging can be concealed and trained on an unwitting subject up to 12 feet away. And the test also can be done quickly, making it potentially useful for checking out travelers seeking to board airliners, as well as would-be CIA agents.

Levine theorizes that the stress of lying leads a person to throw off more heat. But the test sample was tiny, and much remains unknown. He's planning more tests.

Focusing on words

Not all of the research involves high-tech machines.

Researchers at the University of Oklahoma are testing whether a liar's false or incomplete statements contain clues that give him away. To spot a lie, researchers look for words such as "maybe," "possibly" or "to the best of my knowledge."

They say liars also typically offer facts that aren't relevant to an interviewer's main question. An example: a suspect at the scene of a robbery-homicide of a jeweler who describes the diamonds in their display cases in detail, but who gives only a superficial description of the victim's body.

With help from the Polygraph Institute, Oklahoma psychologists Shane Connelly and Mike Mumford are testing more than 120 cues that could be used to detect lies in security screenings. So far, cues developed by the pair have been right about 75% of the time. But the method also has done something the polygraph doesn't do well: reveal deception by people who don't lie, but who hide the truth by leaving out key facts.

"A person doing the deceiving ... has to perform constant self-monitoring and idea generation," Connelly says. "You have a lot more to think about. It shows."

Analyzing voice stress

Some promising ideas have been rejected and sent back to the drawing board. In St. Louis in 2001, researchers at Washington University tested software designed to detect deception in a speaker based on changes in stress levels in his voice. But it identified liars only 24% of the time.

In the mid-1990s, the CIA and FBI tested a device designed to identify deception by using a halo-like helmet to measure brain waves triggered when a subject saw something familiar. Both agencies decided it would be difficult to adapt to interrogations.

So until something better comes along, agencies continue to use the polygraph. Horvath says the government would drop the polygraph "in a minute" if a more effective device were developed. Critics say it should be dropped anyway.

"Is it better than nothing, or worse?" asks Steven Aftergood of the Federation of American Scientists, which has criticized government secrecy. "It's worse if it creates a false sense of security or excludes qualified employees from government service. Any new technology has to pass that test."