pressure goes up, his skin gets sweaty and his respiration increases, heart rate increases and mrs. wyatt calligraphy measures. that's why it's not a good device. what if we didn't ask the body so to speak, but as the brain? it's very, very interesting. i guess a short story is even though some devices seem accurate in the lab, which is a very contained and controlled environment, there is just no good offense they would be affect it in the real world, where for example we are not instructed to lie. that's how these studies have were, even the best of them, the most carefully controlled ones with reasonable sample size is. they instruct people to tell a lie. >> host: they carefully controlled to think they are flying about. did you take the $5 bill at the duster? sunny person with a history to ask a complicated question of whether they are guilty and it had a chance to prepare. and the stakes could matter greatly to and who might be good, better or worse i was the cause, beating the machine. i forgot the word for it, but basically, even people who take a polygraph, they can try to change