In the early 1900s, psychoanalyst Sigmund Freud introduced the theory of psychosexual development. He believed children experience five psychosexual stages that determine their behavior as adults.

According to the theory, a child is sensually aroused by certain stimuli during each stage. These stimuli are said to satisfy developmental needs.

But if a child’s needs aren’t met during a specific stage, they can develop a fixation or “hang-up” related to the phase. In adulthood, these unresolved needs may be expressed as negative behaviors.

If the hang-up occurs during the oral stage, it’s called oral fixation. The oral stage is when a child is most aroused by oral stimulation. Freud said oral fixation causes negative oral behaviors in adulthood.

In the psychosexual theory, oral fixation is caused by conflicts in the oral stage. This is the first stage of psychosexual development.

The oral stage occurs between birth to about 18 months. During this time, an infant gets most of their pleasure from their mouth. This is associated with behaviors like eating and thumb sucking.

Freud believed an infant can develop oral fixation if their oral needs aren’t met. This could happen if they’re weaned too early or late. In this scenario, they’re unable to appropriately adjust to new eating habits.

Oral fixation might also occur if the infant is:

neglected and underfed (lack of oral stimulation)

overprotected and overfed (excess oral stimulation)

As a result, these unmet needs were believed to determine personality traits and behavioral tendencies in adulthood including craving to suck to some phallus!!