A two-component theory of encephalization in mammals

The evolutionary increase in relative brain size in mammals is shown to be correlated with an addition of neuronal elements to the cerebral cortex. From a theory of encephalization, based on these findings, it appears that the number of modules (or neurons) in the cerebral cortex associated with higher order brain functions at the same time depends upon the size of the animal. This supports the thesis that the two major components, which determine the volume of the brain, viz. a body size related component and a non-somatic evolutionary component, are inter-related.