ABSTRACT
One of the most striking changes in the evolution of mammals from an ancestral reptilian stock has been the expansion of neocortical tissue over the surface of the cerebral hemispheres. Though the idea that learning depends on neocortex has a long history there is one serious objection to it, namely that comparative learning studies show that neocortex is manifestly not a prerequisite for learning. In the case of mammals, however, neocortex is present and becomes increasingly well developed in certain mammalian lines. Ivan Pavlov concluded on the basis of studies with dogs which had had neocortex surgically removed that this part of the mammalian brain was essential for learning to take place. If neocortex is not essential for learning in the mammalian brain it is interesting to consider briefly just how much, or how little, of such brains is required for learning to take place.
