Effect of Two Types of Control Questions and Two Question Formats on the Outcomes of Polygraph Examinations

• NCJ Number: 223879
• Journal: Journal of Forensic Sciences Volume: 53 Issue: 4 Dated: July 2008 Pages: 889-899
• Author(s): Frank Horvath Ph.D.; John J. Palmatier Ph.D.
• Date Published: July 2008
• Length: 11 pages
• Sponsoring Agency: American Polygraph Assoc; Michigan State University
• Publication Format: Article
• Publication Type: Report (Study/Research)
• Language: English
• Country: United States of America

Annotation

This study evaluated the effect of two major variations of polygraph “control question” (CQ) testing, the Zone Comparison (ZoC) and the Modified General Question Test (MGQT).

Abstract

Both types of CQs produced similar accuracy, inconclusive excluded, on guilty subjects, 85 percent and 80 percent for nonexclusive and exclusive questions, respectively; this difference was not statistically significant. The difference in accuracy on innocent subjects for the two types of CQs, however, was statistically significant, inconclusive decisions excluded. For the innocent subjects, the nonexclusive CQs (MGQT) produced an accuracy of 91 percent; whereas, the exclusive CQs (ZoC) had an accuracy of only 45 percent. The rationale for CQ testing is based on the assumption that persons who are truthful regarding incident-specific (relevant) test questions will be more concerned about the broader nonincident (control) questions, about which they have doubts, than the relevant questions. Deceptive persons, however, will be more concerned about the relevant questions than about the control questions. Exclusive CQs have no overlap between relevant questions and CQs; whereas with nonexclusive CQs, questions may cover the relevant offense. The gender of the subjects did not produce consistent effects on any of the dependent measures. The results did provide support for the theory posited by advocates of CQ polygraph testing, i.e., that in the context of a specific event, innocent (truthful) and guilty (deceptive) subjects will respond differently to relevant and properly developed CQs. Eighty White males and 40 White females were randomly selected from volunteers recruited from large undergraduate classes in Criminal Justice and Criminology. In a mock theft scenario, subjects were randomly assigned to be either “innocent” or “guilty.” Polygraphic data collected by experienced field examiners were numerically scored by an evaluator blind to all aspects of the study. 5 tables, 2 figures, and 29 references