A look at relative brain size in mammals.

While brain weight scales to body weight, the differences among brain weights are less than those among body weights. It has been assumed that this negative scaling is causally related to an isometric scaling of brain weight with surface area. For this assumption to be true, surface receptor/effector densities must be constant. Morphometric data indicate that this is not the case. Interspecific scaling of mammalian brain sizes, however, is isometric with the organisms' abilities to support the energy costs of the brain.