Predictive power of the polygraph: can the "lie detector" really detect liars?

Area of Science:

• Forensic Science
• Psychological Assessment

Background:

• The polygraph, or lie detector, is increasingly proposed for use in the US and UK.
• Assessing the accuracy of polygraph testing is crucial for its application.

Purpose of the Study:

• To evaluate the positive predictive value of polygraph testing.
• To determine the reliability of polygraph results in identifying deception.

Main Methods:

• Analysis of existing high-quality published data on polygraph sensitivity and specificity.
• Calculation of the positive predictive value based on this data.

Main Results:

• The positive predictive value of the polygraph is often poor in screening and investigative contexts.
• A majority of positive polygraph results are likely to be false positives.
• Truthful individuals are more likely to be falsely identified as deceptive than actual liars are to be correctly identified.

Conclusions:

• The polygraph's utility as a lie detector is questionable due to a high rate of false positives.
• Expanded use of the polygraph may lead to unjust incrimination of truthful individuals.