To deal with cognitive dissonance, or challenges to one's ego, contradictory information was repressed and anxiety was temporarily reduced. Although during the 1960s many laboratory studies on learning and memory and studies of perceptual defense treated the existence of defense mechanisms as empirical fact, in more recent times the concept has begun to fall out of fashion. "Repression was explained by attentional processes and response suppression, while projection was explained by attribution. At least as studied in the laboratory, these processes were not seen to involve unconscious functioning and thus, by definition, did not involve defense mechanisms" (Cramer & Coll 2000). However, defense mechanisms have now been renamed and reformulated under what is currently understood of human psychology. For example, a primitive defense mechanism such as an infant's avoidance of a mother who has abandoned the child seems like an evolutionarily advantageous mechanism -- the need to reject a negligent caretaker (Cramer & Coll 2000). Children who claim to have high esteem often do not, as is revealed upon further questioning by adults, but use such claims as a defense mechanism. Children who experience failure are also more likely to use immature ego-protective defense mechanisms like repression. However, unpleasant emotions and memories are less available to conscious experience in all persons, regardless of age (Cramer & Coll 2000). This can be seen in the mature defense reaction of 'positive illusions' in a patient who is overweight who attributes his or her lack of weight loss solely to a slow thyroid or other circumstances beyond his or her control, despite medical evidence to the contrary. If the patient's size is due to factors beyond his or her control, the patient rationalizes that there is nothing that can be done about his or her excess weight. Emphasizing that "change can come only from the patient, not from the doctor" has been found effective in counteracting this way of thinking (Backalar 2010).

References

Backalar, Nicholas. (2010, October 26). Approach may matter in advice on weight.

The New York Times. Retrieved October 26, 2010 at http://www.nytimes.com/2010/10/26/health/26weight.html?_r=1&ref=health

Cramer, Phebe & Williams Coll. (2000). Defense mechanisms in psychology...

American Psychologist, 55(6): 637-646
According to Sigmund Freud, low self-esteem is rooted in the individual's experience of the so-called 'family Romance.' Individuals try, but may ineffectually repress memories or experiences that challenge their positive sense of self, and only by enabling the client to identify these challenges to his or her ego can a state of true psychological health be attained. According to Freud, however, attaining a state of psychological health was elusive, given the fact that the one's real object of desire was continually displaced and repressed from the beginning of the individual's existence, ever since the development of the desire for the 'phallic mother' in the infant child is thwarted (Hana 1997).

Freud's approach has been much-criticized in recent years, particularly his stress on the universality of how the human mind and self-esteem operates. Not all cultures are based upon a nuclear family structure like the west, or emphasize individuality and autonomy as a condition of psychological health and social normalization. "In North America a key component of constructing the self involves the continual self-affirmation of the individual as an autonomous agent who has functioned, is functioning, and will continue to do so effectively in future, daily social life. In Japan, a key component of constructing the self involves the continual affirmation of the relationships of which the individual is part and thus an affirmation of the self as an active, mutually validating, and validated cultural agent" (Heine et al. 1997). Acting in harmony, rather than acting autonomously is stressed in many cultures. For Freud, being able to autonomously repress the socially negative impulses of the id and to repress negative emotions is seen as integral for self-esteem; in Japan, sublimating personal desires are praised to ensure the continued existence and health of the collective (Heine et al. 1997).