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.
Next: The Oral Stage