In certain ways that involve their brains, some animals are clearly superior to human beings. Eels, salmon, caribou, and many kinds of birds perform astonishing feats of navigation in their long-distance migrations. Owners of dogs or cats know that these mammals have senses of smell and hearing that are better than our own. Behind each such superhuman talent is an area of the animal's brain, enlarged or tailored in some way that makes the special skill possible.
In turn, what distinguishes the human brain from other brains is the relative size of the cerebral cortex, the quarter-inch-thick covering of gray matter on the lobes and hemispheres of the cerebrum. Only in human beings is the cerebral cortex so large in relation to body size.
The human cerebral cortex is further distinguished by its great quantity of foldings and refoldings (convolutions, or gyri), valleys (fissures and sulci) and ridges, all of which increase the surface area of the cortex and allow a maximum amount of gray matter to be packed within the confines of the skull. The brains of lower mammals, with relatively smoother cortexes, have less surface area and less gray matter.
Most scientists agree that the unique abilities of the human brain are directly attributable to the cerebral cortex. The powers of speech and written language, for example, reside there and separate us from other animals. These powers go hand in hand with thinking - observing, analyzing, and integrating experiences to solve problems - planning ahead, and imagining what may happen in the future.