This is the fourth part in a mini-sequence presenting material from Robert Kurzban's excellent book Why Everyone (Else) Is a Hypocrite: Evolution and the Modular Mind.

In the previous post, Strategic ignorance and plausible deniability, we discussed some ways by which people might have modules designed to keep them away from certain kinds of information. These arguments were relatively straightforward.

The next step up is the hypothesis that our "press secretary module" might be designed to contain information that is useful for certain purposes, even if other modules have information that not only conflicts with this information, but is also more likely to be accurate. That is, some modules are designed to acquire systematically biased - i.e. false - information, including information that other modules "know" is wrong.

Kurzban builds up this argument as follows:

Humans are incredibly social. Our intelligence might have evolved exactly because of competition in social domains, living alone and a lack of social interaction are correlated with poor health and unhappiness, and the pain levels reported by people reliving socially painful events, especially ostracism, are "comparable to pain levels reported ... for chronic back pain and even childbirth". Evolution has very strongly wired us for being social and avoiding ostracism and disapproval by the group.

There's a lot of competition in the social world. Our survival and reproduction are determined in large part by how well we navigate the social world. Our minds are likely to have been designed to compete fiercely for the benefits of the social world: the best mates, the best friends, membership in the best groups, and so on.

Social competition is often framed in terms of competing for the best mate or romantic partner, but Kurzban believes that the importance of friendship jealousy is underappreciated. If you are someone's best friend, they are likely to help you in times of need, and to also take your side in nearly all social conflicts. Having many people consider you to be among their best friends is one of the greatest advantages a person can have, and it would be surprising if we didn't have many modules that caused us to try to be valuable for others. People report satisfaction from helping their friends, and of course from making new ones.

We also like to be part of groups. Some groups are very exclusive, ...