behaviorism  -  Field of psychology that flourished in the middle part of the twentieth century in the United States. Attempted to explain all behavior through effect of the environmental contingencies of reward and punishment. For more detail, see Behaviorism.

dependent variable  -  A variable that is not directly manipulated in an experimental study.

experimental study  -  Study in which an independent variable is manipulated in order to determine its effects on a dependent variable.

factor analysis  -  A statistical technique whereby large numbers of self-report questionnaires (or other kinds of data) are reduced to a small number of "factors" that account for most of the variance across people (or other data sources).

humanistic-existential  -  Broad category of personality theories popular in the 1950s, '60s and '70s that focuses on the individual's phenomenology and ability to self-actualize. For more detail, see Humanistic-Existential.

independent variable  -  A variable that is directly manipulated in an experimental study.

observational study  -  Study in which variables of interest are observed, not manipulated.

social cognitive theory  -  Approach to personality that focused on the role of modeling on behavior as well as the role of social influences, expectations, and interpretations on behavior. It is an offshoot of, and related to, behaviorism, but it differs with behaviorism in that it conceives different people as reacting differently (subjectively) to the exact same rewards or punishments.

trait theory  -  The branch of personality psychology that attempts to identify a small number of stable traits that can be used to distinguish between different people using self-report questionnaires. For more detail, see Trait Theory.

temperament  -  A broad characterization of personality, usually with strong assumption of biological influence.