Everything Is Obvious_ _Once You Know the Answer - Duncan J. Watts [8]
If your reaction to this breakthrough insight is that economists need to get out a little more, then you’re not alone. If anything seems like common sense, it’s that people care about fairness as well as money—sometimes even more so. But when the experimenters replicated the game in fifteen small-scale preindustrial societies across five continents, they found that people in different societies have very different ideas about what counts as fair. At one extreme, the Machiguenga tribe of Peru tended to offer only about a quarter of the total amount, and virtually no offers were refused. At the other extreme, the Au and Gnau tribes of Papua New Guinea tended to make offers that were even better than fifty-fifty, but surprisingly these “hyperfair” offers tended to get rejected just as frequently as unfair offers.9
What explains these differences? As it turns out, the Au and Gnau tribes had long-established customs of gift exchange, according to which receiving a gift obligates the receiver to reciprocate at some point in the future. Because there was no equivalent of the ultimatum game in the Au or Gnau societies, they simply “mapped” the unfamiliar interaction onto the most similar social exchange they could think of—which happened to be gift exchange—and responded accordingly. Thus what might have seemed like free money to a Western participant looked to an Au or Gnau participant very much like an unwanted obligation. The Machiguenga, by contrast, live in a society in which the only relationship bonds that carry any expectation of loyalty are with immediate family members. When playing the ultimatum game with a stranger, therefore, Machiguenga participants—again mapping the unfamiliar onto the familiar—saw little obligation to make fair offers, and experienced very little of the resentment that would well up in a Western player upon being presented with a split that was patently unequal. To them, even low offers were seen as a good deal.
Once you understand these features of Au, Gnau, and Machiguenga cultures, their puzzling behavior starts to seem entirely reasonable—commonsense even. And that’s exactly what it was. Just as we reflexively regard fairness and reciprocity as commonsense principles in our world that should be respected in general, and should be defended when violated without good reason, so the people of the fifteen preindustrial societies have their own implicit set of understandings about how the world is supposed to work. Those understandings might be different from ours. But once they have been accepted, their commonsense logic works in exactly the same way as ours does. It is simply what any reasonable person would do if they had grown up in that culture.
What these results reveal is that common sense is “common” only to the extent that two people share sufficiently similar social and cultural experiences. Common sense, in other words, depends on what the sociologist Harry Collins calls collective tacit knowledge, meaning that it is encoded in the social norms, customs, and practices of the world.10 According to Collins, the acquisition of this type of knowledge can be learned only by participating in society itself—and that’s why it is so hard to teach to machines. But it also means that even among humans, what seems reasonable to one might seem curious, bizarre, or even repugnant to another. For example, as Clifford Geertz, the anthropologist, has described, the treatment of hermaphroditic children has varied dramatically across different times and cultures. The Romans abhorred and