Primitive reflexes are automatic, stereotypical movements that are controlled by the brainstem and sometimes by the midbrain. These reflexes are an involuntary response to some type of stimulus and require no thought. The primitive reflexes are the first foundations of the nervous system and assist in brain growth. They are like the base blocks in a a block tower.
Primitive reflexes begin to develop in utero. They serve two purposes. First, primitive reflexes help in the survival of the infant when his/her nervous system is not fully functional (meaning the infant does not have a lot of voluntary control over his/her movements).