Personality, a person's characteristic behavior pattern. Many people think of personality as being made up of observable traits such as shyness, friendliness, and initiative. However, such traits are only the outward expression of various inner conditions and processes such as intelligence, attitudes, interests, and motives. Many psychologists include these inner elements in their definitions of personality.

Normal persons develop relatively consistent personalities that are distinguished by certain dominant traits. Persons belonging to the same cultural group—such as a family or nation—have many traits in common. But each person exhibits different traits under different circumstances, and each has unique traits as well as those he or she shares with others. It is also known that personalities develop throughout life, and may even undergo fundamental changes as a result of psychotherapy or other treatment. For these reasons, psychologists do not believe that personalities can be rigidly classified according to type.

How Personality Is Formed

Personality is produced by the interaction of heredity and environment. Inborn qualities affect the individual's response to the outside world, and the environment influences the way in which inborn capacities develop. However, the precise reasons why one person develops certain personality traits, while another develops other traits, are not known.

Studies of personality origins are limited by the difficulty of making controlled experiments on human behavior. Except for identical twins, no two persons have exactly the same biological inheritance, and even identical twins do not share exactly the same environment. Parents and others respond to each twin differently, providing each with a unique emotional setting.

Inherited Traits

—such as bone structure, skin color, type of hair—play a part in personality only if given a meaning by the environment. For example, an extremely tall boy may develop either shyness or self-confidence, according to whether he is teased because of his height or praised for using it to advantage in playing basketball.

The structure and function of the nervous and glandular systems are inherited qualities having a more direct effect upon personality. Intelligence, talents, and skills are largely dependent upon these systems. However, the effects of even these qualities can be modified by the environment.

External Influences

include both physical environment (climate, geography) and social environment (other individuals, and human institutions). Social influences are considered to be of greater importance in personality formation. Most psychologists believe that basic personality traits are acquired in early childhood, and that the family is therefore of primary importance in forming an individual's personality.

Wider cultural groups such as tribes and nations set up rules, values, and goals, and thus influence personality formation. Diversity within large groups is produced by subcultures such as social and economic classes and religious groups.