Why don't we catch liars? - Truth-Telling, Lying and Self-Deception

Social Research, Fall, 1996 by Paul Ekman

frequencies if they are to go undetected. Equally important, if animals

live in social groups in which some degree of cooperation is essential for

survival, the need for cooperation can reduce the rate at which

unreliable signals are given (1990, p. 189).

To have had some special skill in detecting (or perpetrating for that matter) lies would not have had much adaptive value in such circumstances. Serious, high stake lies probably did not occur that often because of limited opportunity and high costs. When lies were suspected or uncovered, it was probably not by judgments of demeanor. (Note I have focused just on intra-group lies; certainly lies might between groups, and their costs and detection could be quite different).[3]

While there are altruistic lies, my discussion has dealt with less friendly lies, lies that occur when one person gains an advantage, often at the cost of the target of the lie. When the advantage is gained by violating a rule or expectation, we call that cheating. Lies sometimes may be required to accomplish the cheating activity, and lies are always required to conceal having cheated. Those cheated do not typically appreciate being cheated and are motivated to uncover any lies involved. But cheating is not likely to have occurred often enough in our ancestral environment to confer some advantage on those who might have been unusually adept at spotting when it did occur. And as I argued earlier, there was probably so little privacy that cheats would be caught by means other than discerning their misdeeds from their demeanor. The biologist Alan Grafen wrote:

The incidence of cheating must be low enough that signaling remains on

average honest. As signalers maximize their fitness, this implies that the

occasions on which cheating is advantageous must be limited. Perhaps

the signalers for whom cheating is advantageous are in a minority, or

that only on a minority of occasions does it pay a signaler to cheat....

Cheating is expected in evolutionarily stable signal systems, but the

system can be stable only if there is some reason why on most occasions cheating does not pay. Cheats impose a kind of tax on the meaning of the signal. The central fact about stable signaling systems is honesty, and the debasement of the meaning of the signal by cheats must be limited if stability is to be maintained (1990, p. 533)

By this reasoning, signals that cheat, which I would call lies, should have a low incidence. Cosmides and Tooby's (1992) findings suggest that we have evolved a sensitivity to rule infractions and do not reward cheaters, and this may explain why cheating does not occur often. However, our findings suggest that we are not likely to catch cheaters based on our ability to spot their lies from their demeanor but by other means.

To summarize my argument, our ancestral environment did not prepare us to be astute lie catchers. Those who might have been most adept in identifying a liar from demeanor would have had minimal advantage in the circumstances in which our ancestors probably lived. Serious lies probably did not occur often, because a lack of privacy would have made the chances of being caught high. Such a lack of privacy would also mean that lies would typically be discovered by direct observation or other physical evidence, rather than having to rely upon judgments of demeanor. Finally, in a cooperative, closed, small society, when lies are uncovered the reputational costs to the individual would be high and inescapable.