American children spend much of their time passively entertained by television, radio, and movies. In the average American household, the TV set is on for seven hours per day.
In contrast, traditional New Guinea children have virtually no such opportunities for passive entertainment and instead spend almost all of their waking hours actively doing something, such as talking or playing with other children or adults.
Almost all studies of child development emphasize the role of childhood stimulation and activity in promoting mental development, and stress the irreversible mental stunting associated with reduced childhood stimulation.
— Guns, Germs, and Steel by Jared Diamond