Which part of the brain sets humans apart from other animals?

The cerebral cortex is highly developed in humans compared to other mammals and has a much greater volume relative to the rest of the brain.

Generally, however, it is not any single part of the brain but the volume of the cranium (housing the brain) that sets humans apart from other animals. In the course of evolution when the forehead projected outwards, the inner cavity of the skull increased in volume so that more quantity of brain could be contained.