The masses of gray matter that lie deep within the cerebral hemispheres is called cerebral cortex. The cerebral cortex is responsible for many brain functions such as sensation, perception, memory, association, thought, and voluntary physical action. Damage occur to cerebral cortex can leads to many cognitive, sensory, and emotional difficulties in the body. It is also responsible for regulating intensity and precision of voluntary movement.
One of the oldest arguments in the history of psychology is the Nature vs Nurture debate. Each of these sides have good points that it's really hard to decide whether a person's development is predisposed in his DNA, or a majority of it is influenced by this life experiences and his environment.