Some comedians really are funnier than others. Some people really are more beautiful than others. But these are true only because of the kinds of creatures we happen to be; the perceptual apparatus - apparati - that we happen to have.

We scientists have way too much a tendency to simplify problems. I guess it actually comes to us naturally. Take the simplest unit, separate out all the confusing, external factors. Study it. Make sure you understand it. And in psychology that means the person studying the individual. But if you want to study our social nature, if you want to study processes that will lead to war and peace, you don't learn all that much by looking at the single individual. A lot of the important things are emergent facts about us, things that you can only see when you get a lot of us interacting.

The consistent finding of psychological research is that we are fairly accurate in our perceptions of others. It's our self-perceptions that are distorted because we look at ourselves in a rose-colored mirror.

In real life, however, you don't react to what someone did; you react only to what you think she did, and the gap between action and perception is bridged by the art of impression management. If life itself is but what you deem it, then why not focus your efforts on persuading others to believe that you are a virtuous and trustworthy cooperator?

In accounts of men in battle, there is an incredible adrenaline rush from group-versus-group conflict. The fervor and passion of partisans is clearly rewarding; and if it's rewarding, it involves dopamine; and if it involves dopamine, then it is potentially addictive.

Reciprocity is a deep instinct; it is the basic currency of social life.

We can call this "the progress principle": Pleasure comes more from making progress toward goals than from achieving them. Shakespeare captured it perfectly: "Things won are done; joy's soul lies in the doing."