KEY THEME

Trait theories of personality focus on identifying, describing, and measuring individual differences.

KEY QUESTIONS

Suppose we asked you to describe the personality of a close friend. How would you begin? Would you describe her personality in terms of her unconscious conflicts, the congruence of her self-concept, or her level of self-efficacy? Probably not. Instead, you’d probably generate a list of her personal characteristics, such as “outgoing,” “cheerful,” and “generous.” This rather commonsense approach to personality is shared by the trait theories. The trait approach to personality is very different from the theories we have encountered thus far. The psychoanalytic, humanistic, and social cognitive theories emphasize the similarities among people. They focus on discovering the universal processes of motivation and development that explain human personality (Revelle, 1995, 2007). Although these theories do deal with individual differences, they do so only indirectly. In contrast, the trait approach to personality focuses primarily on describing individual differences (Funder & Fast, 2010).

Trait theorists view the person as being a unique combination of personality characteristics or attributes, called traits. A trait is formally defined as a relatively stable, enduring predisposition to behave in a certain way. A trait theory of personality, then, is one that focuses on identifying, describing, and measuring individual differences in behavioral predispositions. Think back to our description of the twins, Kenneth and Julian, in the chapter Prologue. You can probably readily identify some of their personality traits. For example, Julian was described as impulsive, cocky, and adventurous, while Kenneth was serious, intense, and responsible.

People possess traits to different degrees. For example, a person might be extremely shy, somewhat shy, or not shy at all. Hence, a trait is typically described in terms of a range from one extreme to its opposite. Most people fall in the middle of the range (average shyness), while fewer people fall at opposite poles (extremely shy or extremely outgoing).

Most of the terms that we use to describe people are surface traits—traits that lie on “the surface” and can be easily inferred from observable behaviors. Examples of surface traits include attributes like “happy,” “exuberant,” “spacey,” and “gloomy.” The list of potential surface traits is extremely long. Personality researcher Gordon Allport combed through an English-language dictionary and discovered more than 4,000 words that described specific personality traits (Allport & Odbert, 1936).

Source traits are thought to be more fundamental than surface traits. As the most basic dimension of personality, a source trait can potentially give rise to a vast number of surface traits. Trait theorists believe that there are relatively few source traits. Thus, one goal of trait theorists has been to identify the most basic set of universal source traits that can be used to describe all individual differences (Pervin, 1994).

How many source traits are there? Not surprisingly, trait theorists differ in their answers. Pioneer trait theorist Raymond Cattell reduced Allport’s list of 4,000 terms to about 171 characteristics by eliminating terms that seemed to be redundant or uncommon (see John, 1990). Cattell collected data on a large sample of people, who were rated on each of the 171 terms. He then used a statistical technique called factor analysis to identify the traits that were most closely related to one another. After further research, Cattell eventually reduced his list to 16 key personality factors, which are listed in TABLE 11.3.

Cattell (1994) believed that these 16 personality factors represent the essential source traits of human personality. To measure these traits, Cattell developed what has become one of the most widely used personality tests, the Sixteen Personality Factor Questionnaire (abbreviated 16PF). We’ll discuss the 16PF in more detail later in the chapter.

An even simpler model of universal source traits was proposed by British psychologist Hans Eysenck (1916–1997). Eysenck’s methods were similar to Cattell’s, but his conception of personality includes just three dimensions. The first dimension is introversion–extraversion, which is the degree to which a person directs his energies outward toward the environment and other people versus inward toward his inner and self-focused experiences. A person who is high on the dimension of introversion might be quiet, solitary, and reserved, avoiding new experiences. A person high on the extraversion scale would be outgoing and sociable, enjoying new experiences and stimulating environments.

Eysenck’s second major dimension is neuroticism–emotional stability. Neuroticism refers to a person’s predisposition to become emotionally upset, while stability reflects a person’s predisposition to be emotionally even. Surface traits associated with neuroticism are anxiety, tension, depression, and guilt. At the opposite end, emotional stability is associated with the surface traits of being calm, relaxed, and even-tempered.

Eysenck believed that by combining these two dimensions, people can be classified into four basic types: introverted–neurotic, introverted–stable, extraverted–neurotic, and extraverted–stable. Each basic type is associated with a different combination of surface traits, as shown in FIGURE 11.3.

In later research, Eysenck identified a third personality dimension, called psychoticism (Eysenck, 1990; Eysenck & Eysenck, 1975). A person high on this trait is antisocial, cold, hostile, and unconcerned about others. A person who is low on psychoticism is warm and caring toward others. In the chapter Prologue, Julian might be described as above average on psychoticism, while Kenneth was extremely low on this trait.

Eysenck (1990) believed that individual differences in personality are due to biological differences among people. For example, Eysenck proposed that an introvert’s nervous system is more easily aroused than is an extravert’s nervous system. Assuming that people tend to seek out an optimal level of arousal (see Chapter 8), extraverts would seek stimulation from their environment more than introverts would. And, because introverts would be more uncomfortable than extraverts in a highly stimulating environment, introverts would be much less likely to seek out stimulation.

Do introverts and extraverts actually prefer different environments? In a clever study, John Campbell and Charles Hawley (1982) found that extraverted students tended to study in a relatively noisy, open area of a college library, where there were ample opportunities for socializing with other students. Introverted students preferred to study in a quiet section of the library, where individual carrels and small tables were separated by tall bookshelves. As Eysenck’s theory predicts, the introverts preferred study areas that minimized stimulation, while the extraverts preferred studying in an area that provided stimulation.

Many trait theorists felt that Cattell’s trait model was too complex and that his 16 personality factors could be reduced to a smaller, more basic set of traits. Yet Eysenck’s three-dimensional trait theory seemed too limited, failing to capture other important dimensions of human personality (see Block, 1995).

Today, the consensus among many trait researchers is that the essential building blocks of personality can be described in terms of five basic personality dimensions, which are sometimes called “the Big Five” (Funder, 2001). According to the five-factor model of personality, these five dimensions represent the structural organization of personality traits (McCrae & Costa, 1996, 2003).

What are the Big Five? Different trait researchers describe the five basic traits somewhat differently. However, the most commonly accepted five factors are extraversion, neuroticism, agreeableness, conscientiousness, and openness to experience. TABLE 11.4 summarizes the Big Five traits as defined by personality theorists Robert McCrae and Paul Costa, Jr. Note that Factor 1, neuroticism, and Factor 2, extraversion, are essentially the same as Eysenck’s first two personality dimensions.

Does the five-factor model describe the universal structure of human personality? According to ongoing research by Robert McCrae and his colleagues (2004, 2005), the answer appears to be yes. In one wide-ranging study, trained observers rated the personality traits of representative individuals in 50 different cultures, including Arab cultures like those in Kuwait and Morocco and African cultures like those in Uganda and Ethiopia (McCrae & others, 2005). With few exceptions, people could be reliably described in terms of the five-factor structure of personality. Other research has shown that people in European, African, Arab, and Asian cultures describe personality using terms that are consistent with the five-factor model (Allik & McCrae, 2004; Rossier & others, 2005). Based on abundant cross-cultural research, trait theorists Jüri Allik and Robert McCrae (2002, 2004, 2013) believe that the Big Five personality traits are basic features of the human species, universal, and probably biologically based. Some personality researchers, however, are unconvinced, pointing out that there are culturally-specific patterns of behavior that do not easily fit the five-factor model (Carlo & others, 2014). And, recent evidence suggests that the five-factor model may not apply to pre-industrial, preliterate indigenous tribes and developing countries (Gurven & others, 2013). However, these findings seem to be the exception, not the rule.

How can we account for the apparent universality of the five-factor structure? Psychologist David Buss (1991, 1995a) has one intriguing explanation. Buss thinks we should look at the utility of these factors from an evolutionary perspective. He believes that the Big Five traits reflect the personality dimensions that are the most important in the “social landscape” to which humans have had to adapt. Being able to identify who has social power (extraversion), who is likely to share resources (agreeableness), and who is trustworthy (conscientiousness) enhances our likelihood of survival.

Research has shown that traits are remarkably stable over time. A young adult who is very extraverted, emotionally stable, and relatively open to new experiences is likely to grow into an older adult who could be described in much the same way (McCrae & Costa, 2006; McCrae & others, 2000). However, this is not to say that personality traits don’t change at all. Longitudinal data suggest that some general trends are evident over the lifespan. These include a slight decline in neuroticism, an increase in agreeableness and conscientiousness, and stability in extraversion and openness to experience from early to late adulthood (Soto & others, 2011; Kandler, 2012). In other words, most people become more dominant, agreeable, conscientious, and emotionally stable as they mature psychologically (Caspi & others, 2005; Roberts & others, 2006).

Traits are also generally consistent across different situations. However, situational influences may affect the expression of personality traits. Situations in which your behavior is limited by social “rules” or expectations may limit the expression of your personality characteristics. For example, even the most extraverted person may be subdued at a funeral. In general, behavior is most likely to reflect personality traits in familiar, informal, or private situations with few social rules or expectations (A. H. Buss, 1989, 2001).

Given the consistency of traits over time and across situations, many psychologists think that traits may be associated with specific patterns of brain activity or structure (Canli, 2004, 2006). We discuss a recent attempt to investigate the relationship between brain structure and personality traits in the Focus on Neuroscience box, “The Neuroscience of Personality: Brain Structure and the Big Five.”

Keep in mind, however, that human behavior is the result of a complex interaction between traits and situations (Mischel, 2004; Mischel & Shoda, 2010). People do respond, sometimes dramatically, to the demands of a particular situation. But the situations that people choose, and the characteristic way in which they respond to similar situations, are likely to be consistent with their individual personality dispositions (Mischel & Shoda, 1995; Mischel & others, 2002).

Do personality traits run in families? Are personality traits determined by genetics? Many trait theorists, such as Raymond Cattell and Hans Eysenck, believed that traits are at least partially genetic in origin. For example, Sandy and Don’s daughter, Laura, has always been outgoing and sociable, traits that she shares with both her parents. But is she outgoing because she inherited that trait? Or is she outgoing because outgoing behavior was modeled and reinforced? Is it even possible to sort out the relative influence that genetics and environmental experiences have on personality traits?

The field of behavioral genetics studies the effects of genes and heredity on behavior. Most behavioral genetics studies on humans involve measuring similarities and differences among members of a large group of people who are genetically related to different degrees. The basic research strategy is to compare the degree of difference among subjects to their degree of genetic relatedness. If a trait is genetically influenced, then the more closely two people are genetically related, the more you would expect them to be similar on that trait (see Chapter 7).

Such studies may involve comparisons between identical twins and fraternal twins or comparisons between twins reared apart and identical twins reared together (see the In Focus box, “Explaining Those Amazing Identical-Twin Similarities” below). Adoption studies, in which adopted children are compared to their biological and adoptive relatives, are also used in behavioral genetics.

Evidence gathered from twin studies and adoption studies shows that certain personality traits are substantially influenced by genetics (Amin & others, 2011; de Moor & others, 2010; McCrae & others, 2010). The evidence for genetic influence is particularly strong for extraversion and neuroticism, two of the Big Five personality traits (Plomin & others, 1994, 2001; Weiss & others, 2008). Twin studies have also found that openness to experience, conscientiousness, and agreeableness are also influenced by genetics, although to a lesser extent (Bouchard, 2004; Harris & others, 2007).

So is personality completely determined by genetics? Not at all. As behavioral geneticists Robert Plomin and Essi Colledge (2001) explain, “Individual differences in complex psychological traits are due at least as much to environmental influences as they are to genetic influences. Behavioral genetics research provides the best available evidence for the importance of the environment.” In other words, the influence of environmental factors on personality traits is at least equal to the influence of genetic factors (Rowe, 2003). Some additional evidence that underscores this point is that identical twins are most alike in early life. As the twins grow up, leave home, and encounter different experiences and environments, their personalities become more different (Bouchard, 2004; McCartney & others, 1990).

Although psychologists continue to disagree on how many basic traits exist, they do generally agree that people can be described and compared in terms of basic personality traits. But like the other personality theories, the trait approach has its weaknesses (Block, 1995).

One criticism is that trait theories don’t really explain human personality (Epstein, 2010; Pervin, 1994). Instead, they simply label general predispositions to behave in a certain way. Second, trait theorists don’t attempt to explain how or why individual differences develop (Boyle, 2008). After all, saying that trait differences are due partly to genetics and partly to environmental influences isn’t saying much.

A third criticism is that trait approaches generally fail to address other important personality issues, such as the basic motives that drive human personality, the role of unconscious mental processes, how beliefs about the self influence personality, or how psychological change and growth occur (Block, 2010; McAdams & Walden, 2010). Conspicuously absent are the grand conclusions about the essence of human nature that characterize the psychoanalytic and humanistic theories. So, although trait theories are useful in describing individual differences and predicting behavior, there are limitations to their usefulness.

As you’ve seen, each of the major perspectives on personality has contributed to our understanding of human personality. The four perspectives are summarized in TABLE 11.5.

Our discussion of personality would not be complete without a description of how personality is formally evaluated and measured. In the next section, we’ll briefly survey the tests that are used in personality assessment.