A lie detector instrument used to measure truthfulness by analyzing physiological responses?

• A. Polygraph
• B. MRI
• C. EEG
• D. CT Scan

Answer: (A)

Lie detection through physiological responses is assessed with a polygraph, which records signals such as respiration, heart rate, blood pressure, and skin conductance while a person answers questions. The idea is that deception can produce characteristic arousal patterns that differ from truthful responses, and by comparing responses to neutral or control questions with those to relevant questions, the tester looks for changes that may indicate deception. This is what makes the polygraph the instrument described in the prompt. In contrast, MRI measures brain activity or structure, EEG records electrical activity of the brain, and CT scans image the body's internal structures. These tools are not designed as lie detectors in the same way and aren’t used for measuring truthfulness through physiological arousal.