PEOPLE are extraordinarily skilled at spotting cheats 鈥� much better than they are at detecting rule-breaking that does not involve cheating. A study showing just how good we are at this adds weight to the theory that our exceptional brainpower arose through evolutionary pressures to acquire specific cognitive skills.
The still-controversial idea that humans have specialised decision-making systems in addition to generalised reasoning ability has been around for decades. Its advocates point out that the ability to identify untrustworthy people should be favoured evolutionarily, since cheats risk undermining the social interactions in which people trade goods or services for mutual benefit.
To test whether we have a special ability to reason about cheating, , an evolutionary psychologist at the University of California, Santa Barbara, and her colleagues used a standard psychological test called the , which tests volunteers鈥� ability to reason about 鈥渋f/then鈥� statements.
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The researchers set up scenarios in which they asked undergraduate volunteers to imagine they were supervising workers sorting applications for admission to two schools: a good one in a district where school taxes are high, and a poor one in an equally wealthy, but lightly taxed district. The hypothetical workers were supposed to follow a rule that specified 鈥渋f a student is admitted to the good school, they must live in the highly taxed district鈥�.
Half the time, the test subjects were told that the workers had children of their own applying to the schools, thus having a motive to cheat; the rest of the time they were told the workers were merely absent-minded and sometimes made innocent errors. Then the test subjects were asked how they would verify that the workers were not breaking the rule.
Cosmides found that when the 鈥渟upervisors鈥� thought they were checking for innocent errors, just 9 of 33, or 27 per cent, got the right answer 鈥� looking for a student admitted to the good school who did not live in the highly taxed district. In contrast, when the supervisors thought they were watching for cheats, they did much better, with 23 of 34, or 68 per cent, getting the right answer (Proceedings of the National Academy of Sciences, ).
This suggests that people are, indeed, more adept at spotting cheats than at detecting mere rule-breaking, Cosmides says. 鈥淎ny cues that it鈥檚 just an innocent mistake actually inactivate the detection mechanism.鈥�
鈥淧eople appear to be more adept at spotting cheats than at detecting mere rule-breaking鈥�
The result is what you would expect if natural selection had favoured this specific ability in early, pro-social humans 鈥� and is not at all what would happen under selection for generalised intelligence, Cosmides says. 鈥淢y claim is not that there鈥檚 nothing domain-general in the mind, just that that can鈥檛 be the only thing going on in the mind.鈥�
Other psychologists remain sceptical of this conclusion. 鈥淚f you want to conclude that therefore there鈥檚 a module in the mind for detecting cheaters, I see zero evidence for that,鈥� says , a cognitive scientist at Brown University in Providence, Rhode Island. 鈥淚t鈥檚 certainly possible that it鈥檚 something we learned through experience. There鈥檚 no evidence that it鈥檚 anything innate.鈥�
