Infants are naturally and adaptively in an oral stage, but if weaned too early or too late, there may be a subsequent failure to resolve the conflicts of this stage and to develop a maladaptive oral fixation. In later life, these people may constantly "hunger" for activities involving the mouth.
Oral fixations are considered to contribute to over-eating, being overly talkative, smoking addictions and alcoholism (known as "oral dependent" qualities). Other symptoms include a sarcastic or "biting" personality (known as "oral sadistic" qualities).
Critics of Freud's theories doubt that such a thing as "oral fixation" can explain adult behaviors, and that subscribing to this simplistic explanation can prevent the exploration of other possible causes that may occur. Even psychoanalytically oriented practitioners have broadened their understandings of fixations beyond simple stage theory.