Sigmund Freud's theory of psychosexual development outlines five distinct stages that shape personality through the resolution of conflicts associated with pleasure-seeking urges from the id. Each stage is characterized by specific needs and conflicts that, if unresolved, can lead to particular personality traits in adulthood.

The first stage, the oral stage, occurs from birth to about one year of age, where the primary need is oral gratification, typically achieved through breastfeeding or bottle feeding. The major conflict arises during weaning, when the child is suddenly deprived of this source of pleasure. Freud posited that failure to resolve this conflict could result in an oral fixation, leading to behaviors such as smoking, overeating, or nail biting in adulthood.

Next is the anal stage, which spans from ages one to three. Here, the focus shifts to controlling bowel movements, with toilet training presenting the central conflict. Freud identified two potential outcomes based on how this conflict is resolved: an anal-retentive personality, characterized by rigidity and control, or an anal-expulsive personality, marked by messiness and disorganization.

The phallic stage occurs between ages three and six, where children begin to explore their genitals. The key conflict during this stage is the Oedipus complex for boys and the Electra complex for girls, involving feelings of desire for the opposite-sex parent and rivalry with the same-sex parent. Successful resolution leads to identification with the same-sex parent, while failure may result in attention-seeking behaviors and issues with self-worth.

Following this is the latency stage, from ages six to twelve, during which sexual energies are dormant. Children focus on friendships and non-sexual interests, and Freud suggested that there are no significant adult personality consequences from this stage.

Finally, the genital stage begins in adolescence, where the focus returns to sexual exploration and behavior. The conflict here involves aligning sexual urges with societal expectations. Failure to navigate this stage can lead to difficulties in forming intimate relationships in adulthood.

While Freud's observations about developmental milestones, such as the importance of bodily autonomy in toddlers and same-sex friendships in childhood, have some merit, the specific mechanisms he proposed regarding the id and personality outcomes lack empirical support in modern psychology. Freud's theory, while historically significant, is not considered scientifically valid today, though it has contributed to our understanding of developmental psychology.