Personality can be defined as a fairly stable set of characteristics and tendencies that determine the individuality of a person's responses to a variety of environmental circumstances. This definition addresses two key questions: why different people behave differently in the same situation, and what accounts for individual consistency across situations. Personality results from the interplay of biological and environmental factors. Different personality theorists emphasize different aspects of personality and its development.

CONCEPT I: Psychoanalytic Theories

Sigmund Freud was the founder of the psychoanalytic approach to personality, although other theorists have modified and expanded his concepts. All such theorists believe that powerful unconscious motives exist and that conflict between motives produces anxiety and defense mechanisms.

According to Freud, the unconscious is the major motivating force in human behavior. Although we cannot directly experience the contents of the unconscious, the contents can reveal themselves in unguarded moments through such things as slips of the tongue, accidents, and revealing jokes.

Freud divided the human psyche into three separate but interacting motivational forces: id, ego, and superego. The unconscious id contains the psychic energy and biological drives. The id (or "it") operates according to the pleasure principle, seeking immediate gratification and reduction of tension, regardless of circumstances. The ego begins developing soon after birth and helps the innate id to reduce tension realistically. The ego is present in the conscious mind and functions according to the reality principle, seeking rational solutions to satisfy the id's demands. The superego develops in childhood and represents the moral standards of society as conveyed to the person by his or her parents. The superego, commonly referred to as the conscience, functions to prohibit the expression of the id's instinctive drives. Thus, the id and superego are often in conflict, and it is the ego's task to mediate this conflict.

When the ego is losing its struggle to reconcile the demands of id, superego, and reality, anxiety develops. Anxiety is a state of psychic distress and its presence signals that an overwhelming id impulse will lead to some kind of harm. When the ego inhibits the id's harmful demands, the resulting inner conflict is this anxiety.

Anxiety can be reduced by using defense mechanisms. Repression is the most basic defense mechanism; it operates by pushing unacceptable id impulses back into the unconscious. All other defense mechanisms involve repression. Denial is the refusal to acknowledge some threat. Regression reduces anxiety by allowing the person to behave as he or she did at an earlier, less conflict-oriented stage of life. In reaction formation, a person replaces an anxiety-producing impulse or feeling (e.g., hate) with its opposite (e.g., love). Projection occurs when a person unknowingly attaches his or her own objectionable attributes to other people. Displacement is the transfer of unacceptable feelings from their appropriate target to a much safer object; and sublimation is a kind of displacement in which forbidden impulses are diverted toward socially desirable goals. When used in moderation, defense mechanisms can have positive outcomes. They are especially useful in dealing with short-term crisis situations. If they endure, however, they may become the person's only way of handling anxiety and may prevent the development of healthy relationships, thus causing more problems than they solved.

Since Freud believed that early life experiences laid the groundwork for adult personality, he developed an elaborate theory of personality development. Freud argued that, at different stages in a child's life, the id's drive for sexual pleasure centers around different body parts, and that adult personality is shaped by the way the child resolves the conflicts between these early sexual urges and the restrictions imposed by society. Failure to resolve a conflict results in fixation, characterized by the symbolic expression of the conflict throughout life.

The stages in normal development are: the oral stage (where anxiety can result from withholding food when hungry), the anal stage (where anxiety can result from inappropriate toilet training), the phallic stage (in which pleasure focuses on masturbation and conflict comes from inadequate resolution of the Oedipus conflict), the latency stage (in which the sexual impulses remain in the background), and finally the genital stage (in which mature love relationships are possible and sexual intercourse provides pleasure). For Freud, adequate personality development might not result in happiness, but would allow the ability to form relationships and be productive. Although society was shocked at Freud's suggestion of childhood sexuality, Freud believed that sex was one of the powerful impulses that shaped personality.

Post-Freudian psychoanalytic theorists have tended to give increased emphasis to the ego rather than the id. They have also tended to emphasize the process of social interaction in explaining personality development. A third development has been the extension of critical developmental stages throughout life, as seen in the work of Erikson.

Carl Jung and Alfred Adler both broke with Freud over disagreements about psychoanalytic theory. Jung objected to Freud's pessimistic view of the unconscious. To Jung, the unconscious was the source of creativity. He argued that our unconscious also contains the collected memories of the human race, which are reflected in the same way across cultures in their myths, religion, art, and dreams. Jung also saw personality development as a life-long process of striving to reconcile opposing urges. Adler believed that the great human motivation is striving for superiority. Because children are powerless, they experience the inferiority complex, owing to their powerlessness. Hence, early social relationships are of primary importance in Adler's theory.

Karen Horney believed that children feel basic anxiety when their parents are indifferent to them. The basic hostility, or resentment, that develops is repressed and later expresses itself in one of three modes of social interaction: moving toward others (looking for approval), moving against others (finding security in dominating others), or moving away from others (becoming withdrawn). All these self-protective modes produce interpersonal problems.

Erik Erikson agreed with Freud that childhood conflicts and their resolutions are important determinants of later behavior, but he felt the conflicts were social, not sexual, in nature. He also believed that development proceeds throughout adolescence and adulthood, with different fundamental challenges being encountered at each new stage of life.

Ego psychology, a psychoanalytic approach based on ego and represented by the work of Heinz Hartmann, focuses on the ego's own autonomy and independence of function. Object relations theory merges this ego emphasis and the emphasis on social interaction as it focuses upon the infant's social attachments. Margaret Mahler, for example, believed that the separation-individuation process that each child experiences as it separates from its mother will be repeated throughout life. Heinz Kohut emphasized the child's development of a sense of vigor and its sense of being in control as two critical determinants of personality development.

Freud's theory has been criticized on several grounds. First, it is difficult to conduct research about, since sessions are private, and samples are small and biased toward the white, upper middle-class, and fairly well-to-do. Second, the theory may be untestable, since the same behavior may be interpreted in different ways. Third, Freud's theory shows a strong gender bias.

According to Freud, women are ethically inferior to men because they are jealous of men's penises (penis envy) and because they cannot undergo the same Oedipus conflict as boys do (which involves castration anxiety). Because the superego develops from the Oedipus conflict, women are also less achievement oriented. Other psychoanalytic theorists, most notably Karen Horney, object to this conclusion. She believes that men, not women, perceive the anatomical difference and create a self-fulfilling prophecy that produces female inferiority. Despite these criticisms, Freud's theory and concepts have been of enormous importance in establishing a theory of personality.

CONCEPT II: Trait Theories

Whereas psychoanalytic theory deals with how personality develops, trait theories are concerned with what personalities are made of.

Traits are defined as relatively enduring ways in which one individual differs from another. Trait theorists emphasize and try to explain the consistency of human behavior. Personality traits are stable over time; are consistent over situations; and assert that individual differences are the result of differences in strength, number, and combination of traits in a given person.

Gordon Allport identified 5,000 traits which he believed could be grouped into central traits, which characterize each person's personality. Allport believed that people respond differently to the same situation because they have different traits. He also felt that people with the same traits can find different ways of expressing them. Allport also believed that traits are unique to an individual, and that a true picture of a person's characteristics would require an in-depth case study. This is called an idiographic approach.

In contrast, Raymond Cattell is considered a nomothetic theorist because he focused on finding the general, all-encompassing laws of personality. Cattell viewed the study of personality traits as a science, and thought they could be classified. He used factor analysis, a mathematical technique, to identify 16 primary or source traits which describe each person's personality.

Hans Eysenck's nomothetic approach involved standardized tests and statistical tools to support his theory that the traits in personality can be reduced to three major dimensions: neuroticism versus emotional stability, introversion versus extroversion, and psychoticism. He believes that brain activity differences underlie these dimensions; for example, extroverted people have low levels of arousal in the cerebral cortex, causing them to seek more stimulation from the environment. Consequently, different environmental events affect people differently. For example, alcohol, which lowers cortical arousal, makes introverts more extroverted and amphetamines (which increase cortical arousal) make extroverts more introverted.

A consensus regarding five major dimensions of personality now includes Eysenck's neuroticism and extroversion and three other dimensions-openness to experience, agreeableness, and conscientiousness.

Trait theories are criticized on four grounds. First, they do not provide a theory of development. Second, they rely too heavily on statistical analyses and interpretations. Third, they exaggerate the consistency of human behavior. Fourth, they lead to circular reasoning in which traits describe behavior and behavior defines traits. Trait theories are better at describing than explaining behavior.

The Type A personality is defined as an action-emotion complex that can be observed in any person who is aggressively involved in a chronic, incessant struggle to achieve more and more in less and less time. The Type B personality is defined as the absence of these traits. Early research linked Type A personality to coronary heart disease (CHD). Later research showed that Type A behavior was really a composite, and that the characteristic which was linked to CHD was hostility, the tendency to become angry, irritated, rude, and uncooperative. Type A personality and hostility are related to two of the five major personality traits: agreeableness and neuroticism. Several questions about hostility remain: How is it developed? How does it affect the cardiovascular system? How can it be reduced?

CONCEPT III: Social Cognitive Theories

The cognitive view of personality emphasizes the active, conscious dynamics of personality and suggests that individuals interpret events differently due to their memories, beliefs, and expectations.

One form of social cognitive theory stresses observational learning, or learning by watching others. Social cognitive theories also stress that our behavior is shaped by our expectations, which are continually revised through observational learning. Albert Bandura believes that when people believe they can deal effectively with their situations, a characteristic he calls self-efficacy, they are more likely to try new tasks.

Nancy Cantor has identified three basic elements of personality functioning that distinguish one individual from another: schemas (organized sets of knowledge), tasks (the goals we set for ourselves), and strategies (the techniques and procedures we use to work on our life tasks). Other social cognitive theorists emphasize self-schemas, the set of knowledge about the self that guides perception and interpretation of information in a social setting.

Although cognitive social learning and behavioral approaches are becoming more popular and influential, they are nonetheless rather narrow in scope and do not explain why people tend to show consistent behavior in widely varying situations. Furthermore, they do not prove that self-concept determines behavior; perhaps behavior determines self-concept. Finally, they tend to neglect emotions.

CONCEPT IV: Humanistic Theories

The humanistic approach to personality stresses the individual's unique perception of the world and suggests that all people are free to fulfill their own potential. Humanistic approaches contradict the theories which hold that our behavior is determined by forces beyond our control.

From his practices as a psychotherapist, Carl Rogers came to believe that all humans strive toward self-actualization, the fulfillment of their capabilities and potential. He found, however, that his clients (patients) had trouble doing this due to conditional positive regard, the distortion of feelings produced by the withholding of parental love. In order to gain praise from others, the child incorporates into himself conditions of worth ideas the child believes will bring positive regard. Rogers believes children will become healthy and fully functioning if the conditions of worth they experience are few and reasonable. If not, their self-actualization will be blocked.

Abraham Maslow also believed that a person's primary motivation was self-actualization, but that before a person could reach this stage, a hierarchy of needs must first be satisfied. At the bottom of this hierarchy are the fundamental needs of satisfying physical requirements and the need for safety. Next are the psychological needs for love and belonging and for self-esteem. Finally, if these needs are satisfied, one can attend to the highest need-self-actualization-or being all one can be. Unlike Rogers, Maslow analyzed healthy people, both historical figures and present-day persons, to develop his ideas.

Dan McAdams' theory of psychobiography combines humanistic theory with Erikson's theory of psychosocial development. McAdams believes that one's understanding of one's identity is the key to personality, and we are motivated to strive for self-coherence, a view of ourselves as integrated and having a purpose. McAdams argues that our identity develops as we mature and becomes our life story, which can be analyzed in much the same way as a work of literature. The theorist's job, then, is to collect life stories and analyze them for common and individual themes.

Critics of humanistic theories argue that they are too simple, and they are unscientific. They also fail to offer an explicit theory of development, and are sometimes criticized for being romantically naive. They have contributed to the study of personality by refocusing attention on the self and by providing a positive, optimistic view of the human condition.

CONCEPT V: Biological Approaches

Galen, an early Roman philosopher, held that the four main body fluids (phlegm, black bile, blood, and yellow bile) were related to the four main personality characteristics (phlegmatic, melancholic, choleric, and sanguine). Accordingly, imbalance in the fluids produced personality problems, corrected by diet and bathing, thus forming the basis for a biological theory of personality and therapy.

Modern evolutionary approaches argue that to understand the human mind, one must consider the adaptive problems humans faced in our evolutionary past. Successful adaptation is measured by reproductive success, the ability of individuals to reproduce and thereby pass their traits on to the next generation. As an example of this view, Gangestad and Simpson have proposed a model in which females can take two styles of mating: a restricted strategy, in which she waits for a committed mate of lower desirability, or an unrestricted strategy, where she mates more quickly with a more desirable but less committed partner. The restrictive strategy is adaptive in that it tends to help provide stability in the family, and it is most successful when females outnumber males. The unrestrictive strategy is adaptive in that the mate is likely to be more fit with better traits to pass to offspring, and it is favored in a male-rich environment. Birth ratios seem to conform to this model.

Behavioral genetics models suggest that personality comes from genetic contributions of the parents, shared environmental influences, and idiosyncratic (unique to the individual) events.

The psychophysiological approach attempts to explain personality, and focuses on differences among individuals in their physiology, and especially in the nervous system. Eysenck's theory about introverts and extroverts is an example, since it is based on the notion that the differences in personality types are the result of different levels of cortical activity.

Critics of the biological approaches charge that the evolutionary approach can be circular; that the evolutionary and behavioral genetics models cannot explain why, when adaptiveness results in similar structures, personality is variable; and the psychophysiological approach is also circular such that physiological differences may be the result, not the cause, of personality differences. Advocates of these views argue that the merger of psychology and physiology will be productive in the future.

CONCEPT VI: Integrating Different Approaches to Personality

All theories of personality contribute to our understanding, and most psychologists take an eclectic view, adopting strong points from several theories. The major themes that personality theories all address are: the source and degree of conflict in the personality, the importance of external influences, the importance of continuity and consistency, and the emphasis on self-fulfillment as a goal for personality development. The human personality is an immensely complex subject.