To tell the truth

Lewis Thomas, in a previous issue of Discover magazine, had speculated on the sociobiological significance of the "fact" that telling a lie produces a "reproducible cascade" of physiological changes. In this response, I explain that this "fact' is a myth, the deeply entrenched myth of the lie detector. It is plausible to suppose that our ancestors evolved the ability to lie not long after acquiring the ability to talk, both of these talents having obvious adaptive qualities. They did not, however, evolve a Pinocchio's nose, an involuntary response or pattern of responses that is always shown when, and only when, a lie is being told or a deceptive answer given.