A polygraph, often incorrectly referred to as a lie detector test, is a junk science device or procedure that measures and records several physiological indicators such as blood pressure, pulse, respiration, and skin conductivity while a person is asked and answers a series of questions. The belief underpinning the use of the polygraph is that deceptive answers will produce physiological responses that can be differentiated from those associated with non-deceptive answers; however, there are no specific physiological reactions associated with lying, making it difficult to identify factors that separate those who are lying from those who are telling the truth.

पॉलीग्राफ यह एक ऐसी मसीन है जिसका प्रयोग झूठ पकड़ने के लिए किया जाता है। खास कर इसका प्रयोग तब किया जाता है जब किसी अपराध का पता लगाना हो । पॉलीग्राफ टेस्ट मसीन को झूठ पकड़ने वाली मसीन और लाई डिटेक्टर के नाम से भी जाना जाता है। इसकी खोज जॉन अगस्तस लार्सन 1921 ई के अंदर की थी ।