Cheater-Detection Mechanism

Definition

The human brain can be thought of as a computer—an organic one, designed by natural selection to process information in adaptive ways. It is composed of many programs, each of which evolved because it was good at solving a problem of survival or reproduction faced by hunter-gatherer ancestors in the past. The cheaterdetection mechanism is one of these evolved programs. The adaptive problem it evolved to solve is detecting cheaters in situations involving social exchange.

Usage

Whenever you exchange favors, buy things (trading money for goods), or help someone who has helped you, you have engaged in social exchange. It is a way people cooperate for mutual benefit: I provide a benefit of some kind to you, and you reciprocate by providing a benefit to me, either now or later. As a result, we are both better off than we would have been if neither of us had helped the other. Evolutionary biologists demonstrated that social exchange cannot evolve in a species unless those who engage in it are able to detect cheaters, that is, individuals who take benefits from others without providing them in return. Inspired by this finding, psychologists discovered a cheaterdetection mechanism in the human brain: a program that searches for information that could reveal whether a given individual has cheated in a specific social exchange.

Background

Wherever you find humans, you will find them engaging in social exchange: It is as cross-culturally universal and typical of the human species as are language and tool use. Sometimes it is explicit and formal, as [Page 139]when people agree to trade goods or services. Other times it is implicit and informal, as when a woman living in a hunter-gatherer band shares food she has gathered with someone who has helped her in the past.

That people can make each other better off by exchanging favors, goods, and help is so rational and obvious to humans that they take it for granted. But most species cannot engage in social exchange. Its presence in some species but not others says something about the programs that generate social exchange behavior. Operant conditioning produces behavior contingent on rewards received (like social exchange does). But the programs causing this general form of learning are found in all animal species and so cannot be the cause of social exchange (if they were, many or most species would engage in it). Some of our primate relatives do engage in social exchange, so it must not require the special forms of intelligence that humans possess. Indeed, schizophrenia can impair general reasoning and intellectual abilities without impairing one's ability to detect cheaters in social exchange.

Evidence from many reasoning experiments shows that reasoning about social exchange is much better than reasoning about other topics, and it activates inferences not made about other topics. The patterns found indicate that the human brain contains programs that are specialized for reasoning about, and engaging in, social exchange, including a subroutine for detecting cheaters (the cheater-detection mechanism).

Evidence

Consider the following situation: Your mother knows you want to borrow her car, so she says, “If you borrow my car, then you must fill the tank with gas.” This is a proposal to engage in social exchange because it is an offer to provide a benefit conditionally (conditional on your satisfying her requirement—what she wants in return). Cheating is taking the benefit offered without satisfying the requirement that provision of this benefit was made contingent on. So you would have cheated if you had borrowed the car without filling the tank with gas.

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