Pruning, as referred to in Neuropsychology, refers to the natural and lifelong physiological reduction of neurons, synapses and axons that occurs in the brains of mammals, including humans. This occurs primarily between birth and sexual maturity, although the process continues at a slower throughout the lifespan.
When an animal or person is born the brain contains an immense number of potential neural connections that, as the brain grows and the being learns to survive in its environment, reduce as the brain develops necessary and beneficial neural pathways. Neural connections that are not used and needed gradually disappear from the brain as it matures. This is one of these reasons why learning, both skills and academic knowledge (i.e. foreign languages), is much easier in childhood than later in life. Evidence indicates that richness of environment and experience, both in childhood and later life, influences the progress and extent of this neurological pruning.
See also: Pruning Process