Which device measures physiological arousal used in attempts to detect deception and is considered unreliable by most psychologists?

• A. Polygraph
• B. Expressive Behaviors
• C. Cognitive Appraisal
• D. Grit

Answer: (A)

The main idea is why using physiological signals to tell if someone is lying is viewed as unreliable. A polygraph is the device in question; it records several bodily changes—things like heart rate, blood pressure, breathing, and skin conductance—while a person answers questions. The underlying assumption is that lying creates extra arousal, so those signals will shift in identifiable ways when someone deceives. But arousal isn’t unique to lying. It can be caused by anxiety, fear of being caught, or simply being in a stressful situation, and people vary a lot in how their bodies respond. Some liars may show little arousal, and some truth-tellers may become highly aroused. Because there isn’t a consistent, lie-specific pattern across individuals, the method produces many false positives and false negatives. This lack of reliable validity is why psychologists generally doubt its usefulness, and why polygraph results are not considered definitive evidence in many settings. The other options aren’t devices that measure physiological arousal for deception; they refer to observable behaviors, mental evaluation processes, or a personality trait, none of which function as a deception-detection instrument.