Kevin Lewis points us to this article, Lessons From Pinocchio: Cues to Deception May Be Highly Exaggerated, by Timothy Luke, which begins:
Deception researchers widely acknowledge that cues to deception—observable behaviors that may differ between truthful and deceptive messages—tend to be weak. Nevertheless, several deception cues have been reported with unusually large effect sizes, and some researchers have advocated the use of such cues as tools for detecting deceit and assessing credibility in practical contexts. By examining data from empirical deception-cue research and using a series of Monte Carlo simulations, I demonstrate that many estimated effect sizes of deception cues may be greatly inflated by publication bias, small numbers of estimates, and low power. Indeed, simulations indicate the informational value of the present deception literature is quite low, such that it is not possible to determine whether any given effect is real or a false positive.
Indeed, I’ve always been suspicious of people who claim to be able to detect lies by looking at people’s faces. Valuable information can be obtained from facial expressions, that’s for sure, but detecting lies is tough; it can just be a way for people to exercise their prejudices.
That said, when I was a kid, whenever my sister and I had a dispute, she always told the truth and I was always lying, and my parents believed her every time. It was soooo unfair: they’d believe her, even when there was no direct evidence contradicting whatever story I happened to be spinning.