According to Sigmund Freud, personality is mostly established by the age of five. Early experiences play a large role in personality development and continue to influence behavior later in life.

Freud's theory of psychosexual development is one of the best known, but also one of the most controversial. Freud believed that personality develops through a series of childhood stages during which the pleasure-seeking energies of the id become focused on certain erogenous areas. This psychosexual energy, or libido, was described as the driving force behind behavior.

If these psychosexual stages are completed successfully, the result is a healthy personality. If certain issues are not resolved at the appropriate stage, fixation can occur. A fixation is a persistent focus on an earlier psychosexual stage. Until this conflict is resolved, the individual will remain "stuck" in this stage. For example, a person who is fixated at the oral stage may be over-dependent on others and may seek oral stimulation through smoking, drinking, or eating.

1. The Oral Stage

Age Range: Birth to 1 Year

Erogenous Zone: Mouth 

During the oral stage, the infant's primary source of interaction occurs through the mouth, so the rooting and sucking reflex is especially important. The mouth is vital for eating, and the infant derives pleasure from oral stimulation through gratifying activities such as tasting and sucking. the infant also develops a sense of trust and comfort through this oral stimulation. The primary conflict at this stage is the weaning process--the child must become less dependent upon caretakers. If fixation occurs at this stage, Freud believed the individual would have issues with dependency or aggression. Oral fixation can result in problems with drinking, eating, smoking or nail biting.

2. The Anal Stage

Age Range: 1 to 3 years

Erogenous Zone: Bowel and Bladder Control

Focus of the libido was on controlling bladder and bowel movements. The major conflict at this stage is toilet training--the child has to learn to control his or her bodily needs. Developing this control leads to a sense of accomplishment and independence. According to Freud, success at this stage is dependent upon the way in which parents approach toilet training. If parents take an approach that is too lenient, Freud suggested that an anal-expulsive personality could develop in which the individual has a messy, wasteful or destructive personality. If parents are too strict or begin toilet training too early, Freud believed that an anal-retentive personality develops in which the individual is stringent, orderly, rigid and obsessive.

3. The Phallic Stage

Age Range: 3 to 6 Years

Erogenous Zone: Genitals

During the phallic stage, the primary focus of the libido is on the genitals. At this age, children also begin to discover the differences between males and females. Freud also believed that boys begin to view their fathers as a rival for the mother’s affections. The Oedipus complex describes these feelings of wanting to possess the mother and the desire to replace the father. However, the child also fears that he will be punished by the father for these feelings, a fear Freud termed castration anxiety. The term Electra complex has been used to described a similar set of feelings experienced by young girls. Freud, however, believed that girls instead experience penis envy.Eventually, the child begins to identify with the same-sex parent as a means of vicariously possessing the other parent. Psychologists such as Karen Horney disputed this theory, calling it both inaccurate and demeaning to women. Instead, Horney proposed that men experience feelings of inferiority because they cannot give birth to children.

4. The Latent Period 

Age Range: 6 to Puberty

Erogenous Zone: Sexual Feelings Are Inactive

During the latent period, the libido interests are suppressed. The stage begins around the time that children enter into school and become more concerned with peer relationships, hobbies and other interests. This stage is important in the development of social and communication skills and self-confidence.

5. The Genital Stage 

Age Range: Puberty to Death

Erogenous Zone: Maturing Sexual Interests

During the final stage of psychosexual development, the individual develops a strong sexual interest in the opposite sex. This stage begins during puberty but last throughout the rest of a person's life.

Where in earlier stages the focus was solely on individual needs, interest in the welfare of others grows during this stage. If the other stages have been completed successfully, the individual should now be well-balanced, warm and caring. The goal of this stage is to establish a balance between the various life areas.