We borrowed the idea of “modularity” from the cognitive anthropologists Dan Sperber and Lawrence Hirschfeld.30 Modules are like little switches in the brains of all animals. They are switched on by patterns that were important for survival in a particular ecological niche, and when they detect that pattern, they send out a signal that (eventually) changes the animal’s behavior in a way that is (usually) adaptive. For example, many animals react with fear the very first time they see a snake because their brains include neural circuits that function as snake detectors.
