deception test

What Is a Deception Test?

A deception test is a category of polygraph examination that asks the examinee directly about the matter under investigation, measuring physiological responses to determine whether the examinee is being truthful or deceptive about specific behaviours or events. The term distinguishes this approach from recognition-based formats (such as the Concealed Information Test), which assess whether the examinee possesses knowledge they should not have rather than testing for deception directly.

The Two Major Families

Deception tests fall into two broad structural families, each with a fundamentally different approach to question design and data interpretation:

Relevant/Irrelevant (R/I) Technique

The Relevant/Irrelevant technique is the older of the two families, dating to the earliest structured polygraph tests. It compares physiological responses to relevant questions (about the matter under investigation) with responses to irrelevant or neutral questions (about non-threatening topics). While historically significant, the R/I approach has been largely superseded by comparison question formats in validated practice because it lacks a proper internal control mechanism for differentiating deception-related arousal from general nervousness or reactivity.

Comparison Question Technique (CQT)

The Comparison Question Technique is the dominant family of deception tests in modern validated practice. CQT formats compare responses to relevant questions with responses to carefully designed comparison questions that address broader behavioural topics. The theoretical foundation is psychological set: deceptive examinees are expected to respond more strongly to relevant questions (their primary threat), while truthful examinees respond more strongly to comparison questions. Multiple APA-validated techniques exist within the CQT family, including the Backster Zone Comparison, Utah Probable Lie, and Directed Lie Test.

Single-Issue vs. Multi-Issue

Deception tests can be further classified by scope:

• Single-issue tests — Focus on one specific allegation or event. These yield the highest accuracy and produce diagnostic opinions of DI, NDI, or INC
• Multiple-issue tests — Address several topics within a single session, typically used in screening contexts. Results are reported as SR or NSR

Contrast with Recognition Tests

The key distinction between deception tests and recognition tests lies in what they measure. Deception tests ask "Did you do X?" and measure whether the person is lying. Recognition tests — particularly the Concealed Information Test (CIT) and Peak of Tension formats — present multiple items (one relevant, several irrelevant) and measure whether the person recognises the relevant item. Recognition tests can detect concealed knowledge but cannot determine whether a person is being deceptive about a specific behaviour.

Practical Application

The vast majority of polygraph examinations conducted in both law enforcement and private practice are deception tests. Whether investigating criminal allegations, verifying relationship fidelity, monitoring sex offender compliance, or conducting pre-employment screening, the deception test framework underpins the examination structure. For information about booking a polygraph examination, visit our online booking page.