As he grows you will notice a difference in his physical growth and also his motor development. A baby will learn to control the movements of his shoulders before he can direct his fingers or his arms. He will also gain control over his upper leg before he can manage to control his lower leg of his left foot. The movement and motor ability of a baby will slowly become more controlled and complex in progression from head to toe. Even long before he can walk he will make complicated movements of his arms and his legs There is also a stage of growth during infancy which has been called differentiation and integration.
Differentiation means that an infant's abilities becomes increasingly distinct and specific.
He will gain more and more mastery of movement. As he grows his movements will become more specific. He will learn to respond to specific noises and voices. This will form his infant language, which is very complex. Growth progresses from the center of the body toward the periphery.