Gordon Allport is considered the founder of trait theory. Trait theory is sometimes viewed as dry, inflexible, and devoid of paying attention to the rich and interesting developmental aspects of personality that so many students enjoy studying. Those same students would probably be quite surprised to learn that Allport is generally considered to have been humanistic in his approach. It was within his effort to understand the individual, however, that Allport focused on traits, psychological phenomena that allow some ability to predict the behavior of an individual. Allport was also concerned about factors that negatively affect people, such as prejudice. Indeed, in 1954, he published a classic study on prejudice in which he argued that despite all of humanity’s scientific advances we remain “in the Stone Age so far as our handling of human relationships is concerned” (Allport, 1979). This concern for all people likely grew out of his profound spiritual faith (for a collection of Allport’s daily prayer reflections see Bertocci, 1978). Thus, the trait approach to psychology, as envisioned by Allport, was anything but dry and inflexible, and it paid careful attention to the unique value of each individual.
Raymond Cattell provides a dramatic contrast to Allport. His approach to trait theory was purely scientific and mathematical. He focused on psychological testing, and made extraordinary contributions to psychology in this regard. Unfortunately, he was also quite different than Allport with regard to his views on racial, ethnic, and other forms of diversity. Cattell was a staunch advocate of eugenics, the controlled interbreeding of people to enhance desired human traits. He believed that the government should decide how to control the eugenic breeding, that rich people should be encouraged and allowed to have more children than other people, there should be genetic experiments to pursue new and more favorable traits, and once we can identify such favorable traits we should provide prenatal screening and abort those children who will not be good enough (Cattell, 1972).
Hans Eysenck, followed by Paul Costa and Robert McCrae, attempted to identify a smaller number of traits that could be used to provide a reasonable description of an individual’s personality. The Five-Factor Model of personality, identified by Costa & McCrae (see, e.g., McCrae & Costa, 2003), is considered by many to be the culmination of this area of psychology. However, there are many personality traits that are significant factors for certain individuals, but which do not comprise one the five major factors. One example is the sensation-seeking trait described by Marvin Zuckerman (see, e.g., Zuckerman, 1994). As such, Zuckerman represents the approach of many trait theorists today: take a trait of interest, such as sensation-seeking or religiosity, and study it in great detail. In this chapter, we will examine the approaches taken by these theorists, as well as the form of the theories they subsequently presented.