As we pointed out earlier, the primary criterion for a useful theory is its ability to generate research. We also noted that theories and research data have a cyclic relationship: Theory gives meaning to data, and data result from experimental research designed to test hypotheses generated by the theory. Not all data, however, flow from experimental research. Much of it comes from observations that each of us make every day. To observe simply means to notice something, to pay attention.
You have been observing human personalities for nearly as long as you have been alive. You notice that some people are talkative and outgoing; others are quiet and reserved. You may have even labeled such people as extraverts and introverts. Are these labels accurate? Is one extraverted person like another? Does an extravert always act in a talkative, outgoing maimer? Can all people be classified as either introverts or extraverts?
In making observations and asking questions, you are doing some of the same things psychologists do, that is, observing human behaviors and trying to make sense of these observations. However, psychologists, like other scientists, try to be .vv.v-tematic so that their predictions will be consistent and accurate.
To improve their ability to predict, personality psychologists have developed a number of assessment techniques, including personality inventories. Much of the research reported in the remaining chapters of this book has relied on various assessment procedures, which purport to measure different dimensions of personality. For these instruments to be useful they must be both reliable and valid. The reliability of a measuring instrument is the extent to which it yields consistent results.
Personality inventories may be reliable and yet lack validity or accuracy. Validity is the degree to which an instrument measures what it is supposed to measure. Personality psychologists are primarily concerned with two types of validity—construct validity and predictive validity. Construct validity is the extent to which an instrument measures some hypothetical construct. Constructs such as extraversión, aggressiveness, intelligence, and emotional stability have no physical existence; they are hypothetical constructs that should relate to observable behavior. Three important types of construct validity are convergent validity, divergent validity, and discriminant validity. A measuring instrument lias convergent construct validity to the extent that scores on that instrument correlate highly (converge) with scores on a variety of valid measures of that same construct. For example, a personality inventory that attempts to measure extraversión should correlate with other measures of extra-version or other factors such as sociability and assertiveness that are known to cluster together with extraversión. An inventory has divergent construct validity if it has low or insignificant correlations with other inventories that do not measure that construct. For example, an inventory purporting to measure extraversión should not be highly correlated with social desirability, emotional stability, honesty, or self-esteem. Finally, an inventory has discriminant validity if it discriminates between two groups of people known to be different. For example, a personality inventory measuring extraversión should yield higher scores for people known to be extraverted than for people known to be introverted.
A second dimension of validity is predictive validity, or the extent that a test predicts some future behavior. For example, a test of extraversión has predictive validity if it correlates with future behaviors, such as smoking cigarettes, performing well on scholastic achievement tests, taking risks, or any other independent criterion. The ultimate value of any measuring instrument is the degree to which it can predict some future behavior or condition.
Most of the early personality theorists did not use standardized assessment inventories. Although Freud, Adler, and Jung all developed some form of projective tool, none of them used the technique with sufficient precision to establish its reliability and validity. However, the theories of Freud, Adler, and Jung have spawned a number of standardized personality inventories as researchers and clinicians have sought to measure units of personality proposed by those theorists. Later personality theorists, especially Julian Rotter, Hans Eysenck, and the Five-Factor Theorists have developed and used a number of personality measures and have relied heavily on them in constructing their theoretical models.
• The term "personality" comes from the Latin persona, or the mask that people present to the outside world, but psychologists see personality as much more than outward appearances.
• Personality includes all those relatively permanent traits or characteristics that render some consistency to a person's behavior.
• A theory is a set of related assumptions that allows scientists to formulate testable hypotheses.
• Theory should not be confused with philosophy speculation, hypothesis, or taxonomy, although it is related to each of these terms.
• Six criteria determine the usefulness of a scientific theory: (I) Does the theory generate research? (2) Is it falsifiable? (3) Does it organize and explain knowledge? (4) Does it suggest practical solutions to everyday problems? (5) Is it internally consistent? and (6) Is it simple or parsimonious?
• Each personality theorist has had either an implicit or explicit concept of humanity.
• Concepts of human nature can be discussed from six perspectives: (1)
determinism versus free choice, (2) pessimism versus optimism, (3) causality versus teleology, (4) conscious versus unconscious determinants, (5) biological versus social factors, and (6) uniqueness versus similarities in people.
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