The Evolution of Cognitive Brains in Non-mammals

Abstract

The evolution of cognitive abilities is inextricably linked to the evolution of the brain. Although the bulk of the research on brain-cognition evolution has focused on primates and other mammals, increasing evidence from non-mammals also supports a link between cognitive ability and the brain. This is especially true for relationships between cognition and relative brain and brain region sizes. Cross-species comparisons of innovativeness, tool use, and other aspects of cognition indicate that the sizes of the brain and telencephalic regions are important for cognition in birds and fishes. A recent selection experiment has even demonstrated that larger-brained fish have cognitive advantages over smaller-brained fish. However, other studies have yielded mixed evidence. For example, it is unclear whether the social brain hypothesis is applicable to non-mammals or if hippocampus volume accurately reflects spatial abilities in fishes or birds. Some of these uncertainties are due to relatively poor data sets on cognition and brain anatomy in non-mammals. Alternatively, connectivity and neuron numbers might be more appropriate proxies of information processing capacity of a species and hence its cognition. Relating these other aspects of brain anatomy to cognition will deepen our understanding of neural and cognitive evolution and even generate common design principles that support cognitive processes across species.