ABSTRACT
The definition of convergent evolution is a matter of contention. Convergent evolution is contrasted with parallel evolution, which refers to the evolution of similar phenotypes in two related species and to cases where similar phenotypes are the result of similar developmental pathways. If a trait has evolved convergently, then the best explanation for that trait appears to be something other than the phylogenetic relationship between the two species with the trait. Cognition is not directly observable and must be inferred from the brain or behavior. Historically there are two overarching approaches to the comparative study of cognition that differ in their expectations about what type of cognitive mechanisms different species should possess: the general process approach and the ecological approach. Natural selection has undoubtedly shaped cognition but it would be incorrect to single it out as the only factor explaining the convergence or divergence of cognition.
