Harvard psychology professor Daniel Gilbert suggests in a provocative op-ed in yesterday's New York Times that the way humans perceive things makes reciprocity difficult. After describing his childhood experiences sitting in the back seat of the car with his brother ("But he hit me first." "But he hit me harder."), he explains the phenomenon at work:
In a study conducted by William Swann and colleagues at the University of Texas, pairs of volunteers played the roles of world leaders who were trying to decide whether to initiate a nuclear strike. The first volunteer was asked to make an opening statement, the second volunteer was asked to respond, the first volunteer was asked to respond to the second, and so on. At the end of the conversation, the volunteers were shown several of the statements that had been made and were asked to recall what had been said just before and just after each of them.
The results revealed an intriguing asymmetry: When volunteers were shown one of their own statements, they naturally remembered what had led them to say it. But when they were shown one of their conversation partner's statements, they naturally remembered how they had responded to it. In other words, volunteers remembered the causes of their own statements and the consequences of their partner’s statements.
What seems like a grossly self-serving pattern of remembering is actually the product of two innocent facts. First, because our senses point outward, we can observe other people’s actions but not our own. Second, because mental life is a private affair, we can observe our own thoughts but not the thoughts of others. Together, these facts suggest that our reasons for punching will always be more salient to us than the punches themselves--but that the opposite will be true of other people's reasons and other people's punches.
Not only are there psychological barriers to reciprocity, but responding proportionally presents a challenge as well. Gilbert writes:
In a study conducted by Sukhwinder Shergill and colleagues at University College London, pairs of volunteers were hooked up to a mechanical device that allowed each of them to exert pressure on the other volunteer's fingers.
The researcher began the game by exerting a fixed amount of pressure on the first volunteer’s finger. The first volunteer was then asked to exert precisely the same amount of pressure on the second volunteer’s finger. The second volunteer was then asked to exert the same amount of pressure on the first volunteer’s finger. And so on. The two volunteers took turns applying equal amounts of pressure to each other’s fingers while the researchers measured the actual amount of pressure they applied.
The results were striking. Although volunteers tried to respond to each other’s touches with equal force, they typically responded with about 40 percent more force than they had just experienced. Each time a volunteer was touched, he touched back harder, which led the other volunteer to touch back even harder. What began as a game of soft touches quickly became a game of moderate pokes and then hard prods, even though both volunteers were doing their level best to respond in kind.
Each volunteer was convinced that he was responding with equal force and that for some reason the other volunteer was escalating.
Needless to say, there are some implications of this research for international politics (if one can make the levels-of-analysis leap). Gilbert suggests some of the implications in his essay. It's well worth reading.