Maturation theory is the theory of nature. It’s the biological method to human development. It explains human behavior of genetics or biological. It explains it for the individual ages, and for the individual stages. For example; a child learns to write his/her name, because of the genetic factors. This is the only reason for this. Although, you may be thinking, a child might learn to write his/her name because of parental reinforcement. Perhaps he went to a quality preschool and they practiced it everyday! Arnold Gesell historically adopted this theory. He believed this is the way it is and he believed that all development was because genetics. He didn’t believe that it was environmental; at all! There are many researchers that have disagreed with his explanations. They believe that some growth characteristics are from genetics, but not all of the learning.