The big question in this chapter is 'are fish intelligent?' Fish have small brains, in fact, they have the smallest brain relative to body size of all vertebrates. Yet decisions are being made, important details and encounters are memorized, mental maps are constructed of a fish's varied environment, and fish learn by watching one another. Could it be that even a small neural circuitry generates intelligence and learning? A premise here, is that if evolution requires it, intelligent circuitry will be assembled in any brain, even ones with a small number of neurons. Now we begin exploring the evolution of intelligence, and trying to understand the ecological and social forces that may require or influence cognitive skills needed for success and survival in such an environment. An important body of evidence is what evolutionary biologists refer to as 'convergence. Many common physical traits are found in unrelated species because their environment and behaviors require them. That bats and birds both have wings is an example. It makes sense then, that convergent cognitive abilities would also arise. If organisms of all kinds share common cognitive skills such as social learning, teaching, planning for the future and inventing tools, then the neural complex necessary for these skills must develop in simple networks available across species. While neural complexity must align with and influence cognitive and behavioral complexity, common cognitive abilities shared by many species must also be possible with relatively simple brains. What fish studies in this chapter provide information about convergence and cognitive functioning? And what about Morgan's Canon? Its sort of like Ocham's Razor for evolutionary psychology - a principle of parsimony stating that scientists should look for the simplest explanation for an animal's behavior
