I.       Overview of Personality Theory

         From the investigations of Freud during the last decade of the 19th century until the present time, a number of personality theorists have (1) made controlled observations of human behavior and (2) speculated on the meaning of those observations. Differences in the theories of these men and women are due to more than differences in terminology; they stem from differences among theorists on basic issues concerning the nature of humanity.


II.     What Is Personality?

         The term personality comes from the Latin word persona, meaning the mask people wear or the role they play in life, but most psychologists use the term to refer to much more than the face or facade people show to others. Personality refers to a pattern of relatively permanent traits, dispositions, or characteristics that give some consistency to human behavior


III.    What Is a Theory?

         The term theory is often used quite loosely and incorrectly to imply something other than a useful scientific concept. Scientists use theories to generate research and organize observations.

         A.       Theory Defined

         A theory is a set of related assumptions that allows scientists to use logical deductive reasoning to formulate testable hypotheses

         B.       Theory and Its Relatives

         People often confuse theory with philosophy, speculation, hypothesis, or taxonomy. Although theory is related to each of these concepts, it is not synonymous with any of them.

         1.       Philosophy

         Philosophy—the love of wisdom—is a broader term than theory, but one branch of philosophy—epistemology—relates to the nature of knowledge, and theories are used by scientists in the pursuit of knowledge.

         2.       Speculation

         Theories rely on speculation, but that speculation must be based on the controlled observations of scientists. Science is the branch of study concerned with observation and classification of data and with the verification of general laws. Theories are practical tools used by scientists to guide research.

         3.       Hypothesis

         A theory is more general than a hypothesis and may generate a multitude of hypotheses, or educated guesses.

         4.       Taxonomy

         A taxonomy is a classification system, and classification is necessary to science. Taxonomies, however, do not generate hypotheses—a necessary criterion of a useful theory.

         C.       Why Different Theories?

         Psychologists and other scientists have developed a variety of personality theories because they have differed in their personal background, their philosophical orientation, and the data they chose to observe. In addition, theories permit individual interpretation of the same observations, and each theorist has had his or her own way of looking at things.

         D.       Theorists’ Personalities and Their Theories of Personality

         Because personality theories evolve from a theorist’s personality, psychologists interested in the psychology of science have begun to study the personal traits of leading personality theorists and their possible impact on their scientific theories and research.

         E.       What Makes a Theory Useful?

         Scientists use several criteria to evaluate the usefulness of a theory. A useful theory (1) generates research, (2) is falsifiable, (3) organizes data, (4) guides action, (5) is internally consistent, and (6) is parsimonious.

         1.       Generates Research

         One of the most important functions of a theory is to generate research. A useful theory will stimulate both descriptive research and hypothesis testing. Descriptive research provides a framework for an evolving theory whereas hypothesis testing expands our knowledge of a scientific discipline.

         2.       Is Falsifiable

         A useful theory should generate research that can either confirm or disconfirm its major tenets; that is, a useful theory must be both verifiable and falsifiable. A verifiable theory can be supported by research whereas a falsifiable theory is one that can be disconfirmed by research results that are contrary to its basic tenets.

         3.       Organizes Data

         A useful theory of personality must also be able to organize much of what is currently known about personality into some intelligible framework and to integrate new information into its structure; that is, the theory should be able to organize and explain observations gleaned from research.

         4.       Guides Action

         Theories are practical tools in that they provide the practitioner with a road map for making day-to-day decisions.

         5.       Is Internally Consistent

         A useful theory is internally consistent and includes operational definitions, which define concepts in terms of specific operations to be carried out by
the observer.

         6.       Is Parsimonious

         When two theories are equal on the first five criteria, then the simpler, more parsimonious one is preferred.


IV.    Dimensions for a Concept of Humanity

         Personality theorists have had different conceptions of human nature, and the authors list six dimensions for comparing these conceptions. These dimensions include determinism versus free choice, pessimism versus optimism, causality versus teleology, conscious versus unconscious determinants of behavior, biological versus social influences on personality, and uniqueness versus similarities among people.


V.      Research in Personality Theory

         Personality theories, like other theories, are based on systematic research that allows for the prediction of events. In researching human behavior, personality theorists often use various measuring procedures, which must be both reliable and valid. Reliability refers to a measuring instrument’s consistency and includes test-retest reliability and internal consistency. Validity refers to the accuracy or truthfulness of the test and includes predictive validity and construct validity.