法医学研究杂志

Catching Liars in Psychological Evaluations of Criminal Defendants: Comparing Direct vs. Indirect Assessment of Truthfulness

Abstract

Shawn Adair Johnston* , Gabriel Johnston, Alexis Candelier and Dana Powers-Green

This research examines the two-fold question of why people are so poor at detecting deception and why the indirect assessment of veracity may be more accurate than direct assessment. Four statements made by criminal defendants, two true and two deceptive, were rated by participants on a nine item test of veracity. Eight of the items were derived from Criterion-Based Content Analysis and Reality Monitoring, two techniques of verbal content analysis that exhibit good reliability. Scores on these eight items represented the indirect measure of truthfulness while a ninth item, the direct measure, asked participants to rate the overall truthfulness of each statement. Results indicated that the indirect assessment of truthfulness accurately classified a higher percentage of the statements made by the criminal defendants than the direct assessment while also accounting for more of the variance in the rating. The superior accuracy of indirect assessment, however, resulted from its greater ability to accurately identify truthful rather than deceptive statements. Further, the results suggest that direct assessment overwhelmingly relies on a single variable of realism while largely failing to use the seven other items, while indirect assessment utilizes all eight items approximately equally. The results also suggest that a one-step cognitive process is used in determining that a statement is true but that a two-step process is used in determining a statement is deceptive. These results support the idea that people are poor at detecting deception because identifying a statement as deceptive literally requires more cognitive effort than assuming veracity. Indirect assessment is more reliable since it permits the use of multiple sources of information rather than relying on a single attribute.