Despite substantial criticism, polygraphy remains the only biological method of lie detection in practical use today. The authors conducted a blind, prospective, controlled-within-subjects study to compare which would more accurately detect concealed information—scanning the individual's brain via functional magnetic resonance imaging (fMRI), or polygraphy, which monitors an individual's electrical skin conductivity, heart rate and respiration during a series of questions.
Participants secretly wrote down a number between three and eight; during consecutive and counterbalanced fMRI and polygraphy sessions, they were questioned about what number they wrote. The Concealed Information Test (CIT) paradigm was used to evoke deceptive responses about the concealed number. Three experts in fMRI and three in polygraphy independently evaluated each participant’s preprocessed fMRI images and five-channel polygraph data.
The authors found that the fMRI experts were 24% more likely to detect the concealed number than the polygraphy experts. Incidentally, when two out of three raters in each modality agreed on a number, the combined accuracy was 100%. These data justify further evaluation of fMRI as a potential alternative to polygraphy. The sequential or concurrent use of psychophysiology and neuroimaging in lie detection also deserves new consideration.