Study on delayed gratification, children who were best able to wait at four years old were more socially and academically successful as high-school students and earned higher Scholastic Aptitude Test (SAT) scores
18 months to 3 years, child wants to alleviate tension and experience pleasure by moving their bowels, learning to control as part of toilet training, adults can have "anal" personality
3 to 6 years, focuses on genitals, Oedipus complex, Electra complex, superego develops, adults can have jealousy, low self-esteem, promiscuity, selfishness