Although this may not be the most useful theory in psychology, Sigmund Freud's ideas about psychosexual development are very interesting and memorable. This theory is a bit controversial and believed to be pseudoscientific, but Freud thought of it as a way to explain personality development through a series of stages around the erogenous zones. Freud believed that infants experienced sexuality, and without sexual gratification, children could become fixated on a certain stage. The first stage is the oral stage, which focuses on sexual pleasure in the mouth. Infants satisfy themselves with drinking and sucking. The second stage is the anal stage. Children are able to experience pleasure by moving their bowels. This also teaches them to learn to do so at the appropriate time and place. The next step, the Phallic stage, focuses on the child's genitals. The child will become sexually attracted to the opposite sex parent, and feel a rivalry with the same sex parent. For boys this is the Oedipus complex and for girls it is the Electra complex. This part of Freud's theory is the most criticized. The Latency stage is next, during which sexual impulses occur unconsciously. The final stage is the genital stage and sexual impulses become conscious again and mature romantic relationships are possible. These different steps are one of Freud's most interesting theories. However, the lack of research and evidence makes most modern psychologists skeptical.