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Path to the Truth May Lead to the Stomach

November 1, 2005

Measuring GI activity might improve lie detection accuracy, prodigy’s study suggests

By the time Trisha Pasricha was in seventh grade, her gastroenterologist father had taught her “way more” about the workings of the GI system “than any middle school student should know,” she admits.

And growing up, her mother, a former engineer with the Federal Bureau of Investigation, shared stories about the use of lie detectors that intrigued the young girl.

Drawing upon these combined influences, the now 16-year-old high school student came up with a novel use of the electrogastrogram (EGG), a machine that records the stomach’s electrical activity. Perhaps, she thought, the EGG could be used to measure the stress of lying.

Pasricha’s 10th-grade science fair project, “Liar, Liar, Your Stomach’s on Fire,” put that hypothesis to the test. Her efforts eventually led to a second-place award last spring in the behavioral and social sciences category of Intel’s International Science and Engineering Fair, the world’s largest pre-college science competition.

But that was just the beginning of this prodigy’s scientific journey. This week, the study makes its way before experts in the GI community. One of her collaborators, a researcher at the University of Texas Medical Branch in Galveston, will present the study at the American College of Gastroenterology annual meeting, in Honolulu.

According to Pasricha, the findings could lead to an improved polygraph. “The addition of the EGG should theoretically raise the current standard polygraph’s accuracy,” which is about 90 percent, she said.

Polygraph expert Dr. Daniel Langleben, an assistant professor of psychiatry at the University of Pennsylvania School of Medicine, said it is interesting research. Still, he questioned whether EGG can yield a measure of stress that is qualitatively different from that offered by other lie-detection methods.

“Since EGG would be another measure of the peripheral nervous system activity, it would be as prone to anxiety as the rest of the polygraphic measures,” he said.

The EGG is a noninvasive test typically used in diagnosing patients whose stomach muscles or nerves controlling those muscles are not functioning properly. Electrodes placed on the stomach surface pick up electrical rhythms within the stomach.

“You can think of the pattern of the electrical cycle in a similar fashion to the way a stomach contracts during digestion: It begins at the top of the stomach and works its way down,” Pasricha explained. “Normally, this occurs three times per minute.”

For the study, 16 volunteers were given a set of playing cards and told not to reveal them. After taking baseline EGG and electrocardiogram (EKG) readings, each participant was shown pictures of various playing cards on a computer screen. Each image was accompanied by the question, “Is this your card?” Several more questions followed, such as, “Are you absolutely sure?” and “Are you lying?”

The volunteers were instructed to tell the truth as much as possible, except if one of the cards they viewed was in the set they had been given. In that case, they were asked to lie in order to trick the machines. As an incentive, they were offered $20 for a successful deception. In reality, Pasricha already knew what cards the subjects had been given. Simultaneous EGG and EKG recordings were taken of the volunteers during the lying and truth periods.

The findings show a significant change in the frequency of the electrical cycle in the stomach due to lying compared with baseline readings.

“EGG could also distinguish between truth and lying, whereas heart rate monitoring alone could not,” Pasricha added.

Naturally, Dr. P. Jay Pasricha, chief of gastroenterology and hepatology at the University of Texas Medical Branch, her father and a collaborator on the study, is very proud of his daughter’s achievements.

“Most importantly,” he said, “she appeared to truly understand the scientific process and learn how to be completely rigorous and honest in conducting her experiments.”

Now a junior at Clear Lake High School in Houston, Pasricha said she would like to attend Harvard or Oxford. “Either way,” she said, “I would do biological sciences with a minor in journalism because I want to be a medical broadcast journalist.”

More information

For more about polygraphs, visit the American Polygraph Association (www.polygraph.org ).




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