11.5 Trait Theories and Their Biological Basis

Who’s Who in Trait Theory

One of the first trait theorists was Gordon Allport (1897–1967), who created a comprehensive list of traits to describe personality. One primary reason for developing this list was to operationalize the terminology used in personality research; when researchers study the same topic, they should agree on definitions. If two researchers are studying a trait called “vivacious,” they will have an easier time comparing results if they use the same definition. Allport and his colleague carefully reviewed Webster’s New International Dictionary (1925) and identified 17,953 words (out of approximately 400,000 entries in the dictionary) that they proposed were “descriptive of personality or personal behavior” (Allport & Odbert, 1936, p. 24). The list contained terms that were considered to be personal traits (such as “acrobatical” and “zealous”), temporary states (such as “woozy” and “thrilled”), social evaluations (such as “swine” and “outlandish”), and metaphorical and doubtful (such as “mortal” and “middle-aged”). Most relevant to personality were the personal traits, of which they identified 4,504—a little over 1% of all the entries in the dictionary. Surely, this long list could be condensed, reduced, or classified to make it more manageable. Enter Raymond Cattell.

Raymond Cattell (1905–1998) proposed grouping the long list of personality traits into two major categories: surface traits and source traits (Cattell, 1950). Surface traits are the easily observable personality characteristics we commonly use to describe people: She is quiet. He is friendly. Source traits are the foundational qualities that give rise to surface traits. For example, “extraversion” is a source trait, and the surface traits it produces may include “warm,” “gregarious,” and “assertive.” There are thousands of surface traits but only a few source traits. Cattell (1950) proposed that source traits are the product of both heredity and environment (nature and nurture), and surface traits are the “combined action of several source traits”.

Cattell also condensed the list of surface traits into a much smaller set of 171. Realizing that some of these surface traits would be correlated, he used a statistical procedure known as factor analysis to group them into a smaller set of dimensions according to common underlying properties. With factor analysis, Cattell was able to produce a list of 16 personality factors.

These 16 factors, or personality dimensions, can be considered primary source traits. Looking at Figure 11.2, you can see that the ends of the dimensions represent polar extremes. On one end of the first dimension is the reserved and unsocial person; at the other end is the “social butterfly.” Based on these factors, Cattell developed the Sixteen Personality Factor Questionnaire (16PF), which is described in greater detail later in the chapter, in the section on objective personality tests.

FIGURE 11.2Cattell’s 16 Personality FactorsUsing this list of 16 source traits, Raymond Cattell produced personality profiles by measuring where people fell between the two opposing ends of the dimension for each trait.

Sources: Adapted from Cattell (1973b) and Cattell, Eber, and Tatsuoka (1970).

Hans Eysenck (1916–1997) continued to develop our understanding of source traits, proposing that we could describe personalities using three dimensions: introversion–extraversion (E), neuroticism (N), and psychoticism (P) (FIGURE 11.3).

FIGURE 11.3Eysenck’s Dimensions of PersonalityPsychologist Hans Eysenck developed a model showing the range of human personality dimensions. This figure displays only the original dimensions Eysenck studied, but years later he proposed an additional dimension: psychoticism. People who score high on the psychoticism trait tend to be impersonal and antisocial.

Source: Eysenck and Eysenck (1968).

People high on the extraversion end of the introversion–extraversion (E) dimension tend to display a marked degree of sociability and are outgoing and active with others in their environment. Those on the introversion end of the dimension tend to be quiet and careful and enjoy time alone. Having high neuroticism (N) typically goes hand in hand with being restless, moody, and excitable, while low neuroticism means being calm, reliable, and emotionally stable. A person who is high on the psychoticism dimension is likely to be cold, impersonal, and antisocial, whereas someone at the opposite end of this dimension is warm, caring, and empathetic. (The psychoticism dimension is not related to psychosis, which is described in Chapter 13.)

In addition to identifying these dimensions, Eysenck worked diligently to unearth their biological basis. For example, Eysenck (1967) proposed a direct relationship between the behaviors associated with the introversion–extraversion dimension and the reticular formation. According to Eysenck (1967, 1990), introverted people display higher reactivity in their reticular formation than those who are extraverted. An introvert has higher levels of arousal, thus is more likely to react to stimuli, and therefore has developed a pattern of behavior to cope. He may be more careful or restrained, for example. An extravert has lower levels of arousal, and thus is less reactive to stimuli. Extraverts seek stimulation because their arousal levels are low, so they tend to be more impulsive and outgoing.

The trait theories of Allport, Cattell, and Eysenck paved the way for the trait theories commonly used today. Let’s take a look at one of the most popular models.

The five-factor model of personality, also known as the Big Five, is a current trait approach for explaining personality (McCrae & Costa, 1987). This model, developed using factor analysis, indicates there are five factors, or dimensions, to describe personality. Although 100% agreement does not exist on the names of these factors, in general, trait theorists propose they are openness to experience, conscientiousness, extraversion, agreeableness, and neuroticism (McCrae, Scally, Terracciano, Abecasis, & Costa, 2010). Openness is the degree to which someone is willing to try new experiences. Conscientiousness refers to someone’s attention to detail and organizational tendencies. The extraversion and neuroticism dimensions are similar to Eysenck’s dimensions noted earlier: Extraversion refers to degree of sociability and outgoingness; neuroticism, to emotional stability (degree to which a person is calm, secure, and even tempered). Agreeableness indicates how trusting and easygoing a person is. To remember these factors, students sometimes use the mnemonic OCEAN: Openness, Conscientiousness, Extraversion, Agreeableness, and Neuroticism (FIGURE 11.4).

FIGURE 11.4The Five-Factor Model of PersonalityThe mnemonic OCEAN will help you remember these factors.

Source: Adapted from McCrae and Costa (1990).

Empirical support for this model has been established using cross-cultural testing. People in more than 50 cultures, who speak languages as diverse as German, Spanish, and Czech, have been shown to exhibit these five dimensions (McCrae et al., 2000, 2005, 2010). Even the everyday terms used to describe personality characteristics across continents (North America, Europe, and Asia) fit well with the five-factor model (McCrae et al., 2010).

One possible explanation is that these five dimensions are biologically based and universal to humans (Allik & McCrae, 2004; McCrae et al., 2000). Three decades of twin and adoption studies point to a genetic basis of these five factors (McCrae et al., 2000; Yamagata et al., 2006), with openness to experience showing the greatest degree of heritability (McCrae et al., 2000; TABLE 11.4). Some researchers suggest that dog personalities also can be described using similar dimensions, such as extraversion and neuroticism (Ley, Bennett, & Coleman, 2008). And such research is not limited to canines; animals as diverse as squid and orangutans seem to display personality characteristics that are surprisingly similar to those observed in humans (Sinn & Moltschaniwskyj, 2005; Weiss, King, & Perkins, 2006).

More evidence for the biological basis of these five factors is apparent from their general stability over time (Kandler et al., 2010; McCrae et al., 2000). This implies that the dramatic environmental changes most of us experience in life do not have as great an impact as our inherited characteristics. That does not mean personalities are completely static, however; people can experience changes in these five factors over the life span (Specht, Egloff, & Schmukle, 2011). For example, as people age, they tend to score higher on agreeableness and lower on neuroticism, openness, extraversion, and conscientiousness. They also seem to become happier and more easygoing with age, displaying more positive attitudes (Marsh, Nagengast, & Morin, 2013). Yet, a study of forager-farmers in Bolivia indicated that this model of personality was not a good fit for a predominantly illiterate and indigenous “small-scale society” (Gurven, von Rueden, Massenkoff, Kaplan, & Lero Vie, 2013).

“Big,” But Not Universal The five-factor model of personality is useful for the vast majority of people in today’s world, but it does not apply to everyone. The Big Five did not find strong support in a recent study of Bolivia’s indigenous Tsimane people, (Gurven, von Rueden, Massenkoff, Kaplan, & Lero Vie, 2013).

Angel Franco/The New York Times/Redux

Men and women appear to differ with respect to the five factors, although there is not total agreement on how. Schmitt and colleagues reviewed studies from 55 nations and reported that, across cultures, women score higher than men on conscientiousness, extraversion, agreeableness, and neuroticism (Schmitt, Realo, Voracek, & Allik, 2008). Men, on the other hand, seem to demonstrate greater degrees of openness to experience. These disparities are not extreme, however; the variation within the groups of males and females is greater than the differences between males and females. Critics suggest that using such rough measures of personality may conceal some of the true differences between men and women; in order to shed light on such disparities, they suggest investigating models that incorporate 10 to 20 traits rather than just 5 (Del Guidice, Booth, & Irwing, 2012).

Maybe you could have predicted women would score higher on measures of agreeableness and neuroticism; perhaps you would have guessed the opposite. Research suggests that some gender stereotypes do indeed contain a kernel of truth (Costa, Terracciano, & McCrae 2001; Terracciano et al., 2005). Let’s find out if this principle holds true for cultural stereotypes as well.

Taking Stock: An Appraisal of the Trait Theories

Better with Age Japanese calligrapher Kawamatasensei paints a giant character that will go on display at a betting theatre for bike racing. Creativity is associated with the personality trait of openness, which has been linked to longevity.

James Whitlow Delano/Redux

As you can see from the examples above, trait theories have facilitated important psychological research. But like any scientific approach, they have their flaws. One major criticism is that trait theories fail to explain the origins of personality. What aspects of personality are innate, and which are environmental? How do unconscious processes, motivations, and development influence personality? If you’re looking to answer these types of questions, trait theories might not be your best bet.

Trait theories also tend to underestimate environmental influences on personality. As Walter Mischel pointed out, environmental circumstances can affect the way traits manifest themselves (Mischel & Shoda, 1995). A person who is high on the openness factor may be nonconforming in college, wearing unique clothing and pursuing unusual hobbies, but put her in the military and her nonconformity will probably assume a new form.

We are about to wrap up our discussion of the trait theories and move on to the intriguing topic of personality testing. Before we do so, though, let’s look at one final example illustrating the value of trait theories. Which of the Big Five would you guess is linked to longevity?