PERSONALITY - EYSENCK’s Biologically Based Factor Theory

                            Eysenck’s Biologically Based Factor Theory

Overview of biologically based trait theory;

  Every theory of personality discussed so far has downplayed, ignored, or even argued against the biological basis of human personality. Only McCrae and Costa placed even mild emphasis on genetic and biological influences on personality. With Eysenck developed a factor theory much like McCrae and Costa, but because he fundamentally based his taxonomy in both factor analysis and biology, he derived only three, rather than five, dimensions of personality-extraversions/intraversions, neuroticism’stability, and psychoticism/superego. The key fo Eysenck was that the individual differences in people’s personalities were biological, and not merely psychological, aspects of personality. That is, genetic differences lead to structural differences in the central nervous system, including brain structures, hormones, and neurotransmitters, and these differences in biology lead to differences along the three factors of personality, extraversion, neuroticism, and psychoticism.

   Evidence for the biological basis of personality comes from many different sources, including temperament, behavioral genetics, and brain measure research. First, temperament is the biologically based tendency to behave in particular ways from very early in life. In one study, for example,  showed that fetal activity and fetal heart rate predict temperament differences over the first year of life. In particular, a high heart rate in a 36-week-old fetüs foreshadowed less predictable eating and sleeping habits at 3 and 6 months after birth. A high heart rate also predicted a less emotional infant at 6 months after birth. The prenatal environment may play an important role in shaping personality. In fact, the amount of stress the mother experiences during pregnancy may later the infant’s own stress response. That is, infant born to mothers who have experienced an unusual amount of stress during pregnancy tend to have impaired stress function; higher baseline levels of stress hormones; and a faster, stronger, and more pronounced physiological response to stress, all of which persist into childhood.

   Secondly, to understand how heredity affects behavior and personality, psychologist turn to the science of behavioral genetics or the scientific study of the role of heredity in behavior. The extent to which a characteristic is influenced by genetics is known as heritability. Researchers use twin-adoption studies and gene-by-environment studies to study heritability. Twin-adoption studies research into hereditary influence on twins, both identical and fraternal, who were raised apart and who were raised together.

  Thirdly, biological aspects of personality are assesed using brain imaging techniques, the two most common froms of which are the electroencephalography and functional magnetic resonance imaging. Researchers use EEG to record the electrical activity of the brain.the procedure involves placing electrodes on a person’s scalp. The electrodes, metal disks attached to wires, are usually mounted in a fabric cap that fits snugly over the head. Typically, the person is conducting certain tasks while electrical activity is recorded. EEG is superior to other brain imaging techniques in showing when brain activity occurs. It is not very accurate at indicating precisely where activity occurs.

Eysenck’s factor theory:

  The personality theory of Hans Eysenck has strong psychometric and biological components. However, Eysenck contended that psychometric sophistication alone is not sufficent to measure the structure of human personality and that personality dimensions arrived at through factor analytic methods are strike and meaningless unless they have been shown to process a biological existance.

Criteria for identifying factors:

  Wtih these assumptions in mind, Eysenck listed four criteria for identifying a factor. First, psychometric evidence fort he factor’s existence must be established. A corollary to his criterion is that the factor must be reliable and replicable. Other investigators, from separete laboratories, must also be able to find the factor, and these investigators consistently identify Eysenck’s extraversions, neuroticism, and psychoticism.

  A second criterion is that the factor must also possess heritability and must fit an established genetic model. This criterion eliminates learned characteristics, such as the ability to mimic the voices of well-known people or a religious or political belief.

  Third, the factor must make sense from a theoretical view. Eysenck employed the deductive method of investigation, beginning with a theory and then gathering data that are locially consistent with that theory.

 The final criterion fort he existence of a factor is that it must possess social revelance; that is, it must be demostrated that mathematically derived factors have a relationship with such socially relevant variables as drug addiction, proneness to unintentional injuries, outstanding performance in sports, psychotic behavior, criminality, and so on.

Personality and behavior:

  According to Eysenck model psychoticism, extraversion, and neuroticism should predict results of experimental studies as well as social behaviors. Recall that Eysenck’ theory assumes that extraversion is a product of low cortical arousability. Therefore, introverts, compared with extraverts, should be more sensitive to a variety of stimuli and learning conditions. Eysenck argued that an effective theory of personality should predict both proximal and distal consequences. Eysenck further argued that many psychology studies have reached erroneous conclusions because they have ignored personality factors. For example, studies in education comparing the effectiveness of discovery learning and traditional reception learning have often produced either concflicting differences or no differences. Eysenck believed that these studies did not consider that extraverted children prefer and do better with the more active discovery learning, whereas introverted children prefer and do better with the more passive reception learning. In other words, an interaction exists between personality dimensions and learning styles. However, when investigators ignore these personality factors, they may find no differences in the comparative effectiveness of discovery versus reception learning styles. Eysenck also hypothesized that psychoticism is related to genius and creativity. Again, the relationship is not simple. Many children have creative ability, are nonconforming, and have unorthodox ideas;  but they grow up to be noncreative people. Eysenck found evidence that these people lack the persistance of high p scorers.

Critique of Eysenck’s biologically based theory:

  Trait and factor theories receive a moderate to high rating. Some of Eysenck,’s research results-for example, his investigations of personality and disease-have not been replicated by outside researchers. His biological theory, because it makes specific predictions, is falsifiable. Trait and factor theories are rated high on their ability to organize knowledge. Because Eysenck’ model of personality is one of the few to take biology seriously, it is one of the only theories that can explain the observation that individuals differ in behavior at birth and that genetics accounts for roughly half of the variablity in individuals differences. Usefull theory has the power to guide the actions of practitioners, and on this criterion, biological theories rank relatively low. Although these theories do a good job of explaining the origins of personality differences, they do not easily lend themselves to practical guides for teachers, parents, an deven counselors. On this criterion, biological theory rates relatively low. The final criterion of useful theory is parsimony. Like McCrae and Costa’s five-factor model, Eysenck’ model of personality is also based on factor analysis with only three majör dimensions, Eysenck model is even more parsimonious than the five-factor approach.