Which deception-detection tool measures physiological responses such as heart rate and skin conductance but is considered unreliable by most psychologists?

• A. Academic Achievement
• B. Cognitive Appraisal
• C. Grit
• D. Polygraph

Answer: (D)

Deception detection using physiological responses hinges on the idea that lying alters autonomic arousal, which a polygraph is designed to detect. A polygraph records signals like heart rate, skin conductance, respiration, and blood pressure while a person answers questions, with the assumption that deceptive responses provoke measurable changes.

But many psychologists question its reliability because arousal is not specific to lying. Nervousness, fear, embarrassment, or even simply being in a stressful interview can heighten these signals, while some honest people may show strong arousal, and some deceivers can suppress or mask their responses. Individual differences, test conditions, and the examiner’s interpretations add further variability. This leads to higher rates of false positives and false negatives, making polygraph results inconsistent across contexts and populations. Because of these issues, polygraphs are regarded as unreliable for accurately detecting deception by most psychologists.

So, the tool described—measuring physiological responses to infer truthfulness but lacking reliability—fits the polygraph.