Birth of a salesman

Natural History, Oct, 2004 by Stephan Reebs

Primatologists have long speculated that, among monkeys and apes, there is a correlation between the brain size of a species--particularly the size of the neocortex--and the species' social skills. But social skills are not easy to define, much less measure directly. Now Richard W. Byrne and Nadia Corp, both psychologists at the University of St. Andrews in Fife, Scotland, have identified a social skill they can count: ordinary acts performed in a way that deceives, and thus manipulates, other animals of the same species, and that benefit the deceiver.

Byrne and Corp synthesized field studies that had reported on the frequency of individual attempts at deception in a total of eighteen species of apes, monkeys, and prosimians. Some of the field investigators had noted, for instance, how often individual troop members hid when they engaged in activity deemed illicit by the dominant animals. Sure enough, when Byrne and Corp matched neocortex size with the number of attempts to deceive, they found that the bigger the neocortex (either in absolute terms, or relative to the rest of the animal's brain), the more deceptions were observed.

It's useful to remember that the size of the human brain is largely the result of its bigger neocortex--a structure that apparently evolved, at least in part, both to deceive and to detect others' attempts at deception. Poker, anyone? ("Neocortex size predicts deception rate in primates," Proceedings of the Royal Society of London B 271:1693-99, August 22, 2004)