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Cleve Backster, a renowned figure in the field of polygraph science, made significant contributions to the advancement of deception detection techniques. One of his most influential developments is the “Either-Or” Rule, which remains a key principle in polygraph examinations today. This rule is fundamental in differentiating between truthful and deceptive individuals by evaluating physiological responses to relevant and control questions. In this article, we explore the origins, application, and significance of Backster’s “Either-Or” Rule and its continued relevance in modern polygraph testing.
Origins of the “Either-Or” Rule
The “Either-Or” Rule emerged from Backster’s work in the 1960s when he sought to create a more reliable method for detecting deception during polygraph examinations. Polygraph testing had already been in use for several decades, but Backster identified the need for a more structured approach to interpreting physiological data.
The essence of the rule is simple: when a person exhibits a greater physiological response to relevant questions (those directly related to the matter under investigation) compared to control questions (designed to elicit a baseline response), the individual is likely being deceptive. Conversely, if the response to control questions is stronger, the individual is likely being truthful. This binary approach—either a stronger reaction to relevant questions or to control questions—became known as the “Either-Or” Rule.
The Function of Control and Relevant Questions
To understand the importance of the “Either-Or” Rule, it’s essential to grasp the role of control and relevant questions in a polygraph test. Control questions are typically broad and emotionally charged, but unrelated to the specific incident being investigated. Their purpose is to establish a baseline response, allowing examiners to measure how the subject’s body reacts when they are not under the stress of lying about a specific event.
Relevant questions, on the other hand, directly pertain to the event or issue under investigation. These questions are designed to provoke a response from a deceptive individual because they carry a higher emotional and cognitive load. The “Either-Or” Rule asserts that a deceptive person will exhibit stronger physiological reactions—such as increased heart rate, blood pressure, or electrodermal activity—when confronted with relevant questions, as opposed to the control questions.
Application of the “Either-Or” Rule in Polygraph Testing
The “Either-Or” Rule is applied throughout polygraph examinations to analyze physiological data and draw conclusions about the subject’s truthfulness. Examiners rely on tools such as pneumographs, cardiographs, and galvanic skin response sensors to measure the physiological changes triggered by control and relevant questions.
The rule works by comparing the subject’s reactions to both types of questions. For example:
- Deceptive individuals tend to show heightened physiological responses (e.g., spikes in heart rate or skin conductivity) when asked relevant questions about a crime or issue they are trying to hide.
- Truthful individuals are more likely to display stronger reactions to control questions because they may feel anxious about the test itself, rather than the specific incident under investigation.
The results of these comparisons are then used to make a determination about the subject’s truthfulness. If the physiological response is stronger during relevant questions, the examiner concludes deception; if stronger during control questions, the subject is deemed truthful.
The Significance of the “Either-Or” Rule in Reducing False Positives and Negatives
Backster’s “Either-Or” Rule significantly improved the accuracy of polygraph tests by reducing both false positives (where a truthful individual is wrongly identified as deceptive) and false negatives (where a deceptive individual is wrongly identified as truthful). Before the introduction of this rule, polygraph interpretation was often subjective and could easily be influenced by an examiner’s bias or misinterpretation of the data.
The “Either-Or” Rule introduces a more objective, data-driven approach to polygraph testing. By focusing solely on the physiological differences between responses to control and relevant questions, the rule eliminates many of the ambiguities that previously plagued polygraph examinations.
Research and Validation of the “Either-Or” Rule
Numerous studies have supported the validity of Backster’s “Either-Or” Rule, demonstrating its effectiveness in identifying deception. Research conducted by polygraph experts, including Cleve Backster himself, consistently shows that subjects who lie exhibit marked physiological responses to relevant questions, while truthful individuals show stronger reactions to control questions due to generalized anxiety or nervousness.
In addition, polygraph techniques such as the Zone Comparison Test (ZCT) and the Matte Quadri-Track Zone Comparison Test (MQTZCT) are based on Backster’s principle. The integration of the “Either-Or” Rule into these techniques has enhanced the accuracy and reliability of polygraph examinations in both field and laboratory settings.
Critiques and Limitations of the “Either-Or” Rule
Despite its widespread use, the “Either-Or” Rule is not without its critics. Some researchers argue that the rule oversimplifies the complexity of human emotions and physiological responses. For example, a truthful person may exhibit strong reactions to relevant questions simply because they are anxious about the consequences of being wrongly accused. This phenomenon, known as the Othello Error, presents a challenge to the “Either-Or” Rule’s assumption that stronger responses to relevant questions always indicate deception.
Furthermore, the rule’s success largely depends on the skill of the examiner. A poorly trained examiner may misinterpret the data, leading to incorrect conclusions. For this reason, Backster himself emphasized the importance of thorough training and strict adherence to testing protocols when applying the “Either-Or” Rule.
Modern Adaptations of the “Either-Or” Rule
In contemporary polygraph science, the “Either-Or” Rule continues to play a crucial role, though it has been adapted and refined over time. Advances in technology, such as computerized polygraph systems, allow for more precise measurements of physiological responses, further reducing the risk of examiner error. In addition, some modern techniques, like the Directed Lie Test (DLT), incorporate variations of the “Either-Or” Rule to fit specific investigative needs.
The principle remains a cornerstone in validated polygraph techniques, influencing the development of new methodologies aimed at enhancing accuracy and minimizing errors in deception detection.
Conclusion
Backster’s “Either-Or” Rule is a foundational principle in polygraph testing, offering a clear, data-driven method for distinguishing between truthful and deceptive individuals. By comparing physiological responses to control and relevant questions, the rule provides a reliable framework for detecting deception, reducing both false positives and negatives. While the rule is not without its limitations, its effectiveness has been validated through decades of research and field application. As polygraph technology and techniques continue to evolve, Backster’s rule remains a critical component of modern polygraph science, ensuring that investigators can rely on objective physiological data to uncover the truth.
Sources:
- Backster, C. (1963). Polygraph Technique and the “Either-Or” Rule. Journal of Polygraph Studies.
- Nelson, R. (2019). Evaluating the Role of Control Questions in Polygraph Testing. Polygraph Science Review, 48(2).
- Matte, C. H. (1989). Application of Backster’s “Either-Or” Rule in Modern Polygraphy. Forensic Credibility Assessments, 32(1).
- American Polygraph Association (2011). Meta-Analytic Survey on Polygraph Accuracy. Polygraph Journal, 47(3).
