Magazine article Clinical Psychiatry News
P300 Detects Information over the Long Term
CHICAGO -- The P300 event-related potential can detect concealed information over an extended period of time, Shinji Hira, Ph.D., said at the annual meeting of the Society for Psychophysiological Research.
The P300 amplitude correctly identified all subjects in a mock crime experiment as guilty, not only when they were tested immediately after the crime, but also when tested a month later and a year later, said Dr. Hira of the University of East Asia in Yamaguchi, Japan.
"Our results suggest the P300 is still feasible even after 1 year has passed from a criminal act," Dr. Hira said. "The P300 is a promising measure for detecting guilty knowledge."
Lie detection through the use of the polygraph system remains a highly controversial application in psychophysiology. However, there is a broad consensus that the concealed information test (CIT) is an accurate technique to detect hidden information, he said.
The test is based on a basic psychophysiologic principle of enhanced orienting responses to significant stimuli. It has applications in both criminal and clinical investigations, as it could be used to determine whether a given patient is amnesic regarding certain information.
In the CIT, a person is presented with a series of multiple-choice questions, each having one relevant (crime-related) and several control answers, while physiologic responses are measured. For example, in a criminal investigation, a person could be interrogated on his or her knowledge of the type of weapon used or place where the victim was found.
If the suspect shows a consistent pattern of differential responding to the correct alternative, one can reasonably assume that he or she has concealed knowledge about that crime, Dr. Hira explained.
More recently, it has been argued that reaction times and evoked potentials offer a promising alternative to autonomic measures. …