be improved by more talking with babies or rewarding them for making speech sounds. Kagan (1979) claimed that children, who were reared in middle-class American homes, begin to speak one year earlier than children reared in some villages such as San Marcos due to the fact that these children, culturally, have little “verbal interaction” with adults. This research assures the importance of the environments, nurture, in early human development.
In conclusion, psychologists and scientist have been arguing as to whether nature or nurture has more influence on early human development. As a result both heredity or the nature and environment or nurture are important factors in shaping human personality, but environment is the more important one. Because nature only goes so far whereas further growth and development is formed by the environment's influence on early human development.