cognition for social exchange
It has been known for years that people are bafflingly bad at the Wason Test which is a simple logical puzzle. However, in an elegant series of tests, Leda Cosmides and John Tooby discovered that if this same test is presented differently — as a social contract that has to be enforced — then people find it much, much easier.
The Wason Test: There are four cards on the table, each has a number on one side and a is coloured on the other. The visible faces of the card show 3, 8, red and brown. Question: Which cards should you turn over to test the proposition that if a card shows an even number on one side, then its opposite face shows a primary colour?
The Wason Test expressed as a social contract: You are a bouncer in a Boston bar and you will lose you job unless you enforce the following law: if a person is drinking beer, then s/he must be over 20 years old'. Question: Which two cards below do you need to turn over to see if someone is breaking the law?
The answer in both cases is the first and the last card. The two problems are logically identical. However, people consistently fail in the first test (answer: 3 and brown) and do considerably better in the second (drinking beer, 16 years old). What these experiments showed was that people did not treat the puzzles as tests of logic at all; they treated them as social contracts and looked for cheats. Further work by Cosmides and Gerd Gigerenzer showed that social familiarity was not a factor in people's performance.
A video interview, The Evolution of the Human Mind, with Leda Cosmides can be viewed from here. An edge.org interview with Gerd Gigerenzer can be viewed from here.