Freudian and humanistic theories shared a common goal: Explain how our personality develops. They focused on the forces that act upon us. Trait researchers, led by the work of Gordon Allport (1897–1967), have been less concerned with explaining traits than with describing them. They define personality as a stable and enduring pattern of behavior, such as Lady Gaga’s openness to new experiences and self-discipline. These traits help describe her personality.

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Imagine that you’ve been hired by an online dating service. Your job is to construct a questionnaire for a new app that will better help people describe themselves to those seeking dates and mates. With millions of people using such services each year, the need to understand and incorporate psychological science grows more important (Finkel et al., 2012a,b). What personality traits might give an accurate sense of the person filling out your questionnaire? You might begin by thinking of how we describe a pizza. We place a pizza along several trait dimensions. It’s small, medium, or large; it has one or more toppings; it has a thin or thick crust. By likewise placing people on trait dimensions, we can begin to describe them.

Basic Factors

An even better way to identify our personality is to identify factors—clusters of behavior tendencies that occur together (McCabe & Fleeson, 2016). People who describe themselves as outgoing, for example, may also say that they like excitement and practical jokes and dislike quiet reading. This cluster of behaviors reflects a basic factor, or trait—in this case, extraversion. (For more about extraversion’s opposite, see Thinking Critically About: The Stigma of Introversion.)

So how many traits will be just the right number for success with your dating questionnaire? If psychologists Hans Eysenck and Sybil Eysenck [EYE-zink] had been hired to do your job, they would have said two. They believed that we can reduce many normal human variations to two basic dimensions: Extraversion–introversion and emotional stability–instability (FIGURE 12.3). People in 35 countries, from China to Uganda to Russia, have taken the Eysenck Personality Questionnaire. The extraversion and emotionality factors emerged as basic personality dimensions (Eysenck, 1990, 1992).

Biology and Personality

As you may recall from the twin and adoption studies discussed in Chapter 3, our genes have much to say about the temperament and behavioral style that help define our personality. Children’s shyness, for example, seems related to differences in their autonomic nervous systems. Infants with reactive autonomic nervous systems respond to stress with greater anxiety and inhibition (Kagan, 2010).

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Brain activity appears to vary with personality as well. Brain-activity scans suggest that extraverts seek stimulation because their normal brain arousal is relatively low. Also, a frontal lobe area involved in restraining behavior is less active in extraverts than in introverts (Johnson et al., 1999).

Personality differences among dogs are as obvious to researchers as they are to dog owners. Such differences (in energy, affection, reactivity, and curious intelligence) are as evident, and as consistently judged, as personality differences among humans (Gosling et al., 2003; Jones & Gosling, 2005). Monkeys, bonobos, chimpanzees, orangutans, and even birds also have stable personalities (Weiss et al., 2006, 2015). Among the Great Tit (a European relative of the American chickadee), bold birds more quickly inspect new objects and explore trees (Groothuis & Carere, 2005; Verbeek et al., 1994). Through selective breeding, researchers can produce bold or shy birds. Both have their place in natural history. In lean years, bold birds are more likely to find food; in abundant years, shy birds feed with less risk.

It helps to know that a potential date is an introvert or an extravert, or even that the person is emotionally stable or unstable. But wouldn’t you like more information about the test-taker’s personality before matching people as romantic partners? The Minnesota Multiphasic Personality Inventory (MMPI) might help. Personality inventories, including the famous MMPI, are long sets of questions covering a wide range of feelings and behaviors. Although the MMPI was originally developed to identify emotional disorders, it also assesses people’s personality traits. Whereas most projective tests (such as the Rorschach) are scored subjectively, personality inventories are scored objectively. Objectivity does not, however, guarantee validity. People taking the MMPI for employment purposes can give the answers they know will create a good impression. But in so doing they may also score high on a lie scale that assesses faking (as when people respond False to a universally true statement, such as “I get angry sometimes”). The objectivity of the MMPI has contributed to its popularity and to its translation into more than 100 languages.

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Today’s trait researchers rely on five factors (called the Big Five) to understand personality—conscientiousness, agreeableness, neuroticism, openness, and extraversion (TABLE 12.3) (Costa & McCrae, 2011; John & Srivastava, 1999). Work by Paul Costa, Robert McCrae, and others shows that where we fall on these five dimensions reveals much of what there is to say about our personality. Some clinical psychologists have begun to use the Big Five to understand personality disorder and dysfunction (Widiger et al., 2016).

As the dominant model in personality psychology, Big Five research has explored various questions:

To find out how your personality measures up, try the brief self-assessment in FIGURE 12.4. If you work the Big Five traits into your dating questionnaire, your mission should be accomplished—if people act the same way at all times and in all situations, that is. Do they?

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To be useful indicators of personality, traits would have to persist over time and across situations. Friendly people, for example, would have to act friendly at different times and places. In some ways, our personality seems stable. Cheerful, friendly children tend to become cheerful, friendly adults. But it’s also true that a fun-loving jokester can suddenly turn serious and respectful at a job interview. Major life events, such as becoming unemployed, can shift our personality from agreeable to slightly rude (Boyce et al., 2015). The personality traits we express change from one situation to another.

The Person-Situation Controversy

Many researchers have studied personality stability over the life span. A group of 152 long-term studies compared early trait scores with scores for the same traits seven years later. These comparisons were done for several different age groups, and for each group, the scores were positively correlated. But the correlations were strongest for comparisons done in adulthood. For young children, the correlation between early and later scores was +0.3. For college students, the correlation was +0.54. For 70-year-olds, the correlation was +0.73. (Remember that 0 indicates no relationship, and +1.0 would mean that one score perfectly predicts the other.)

As we grow older, our personality traits stabilize. Interests may change—the devoted collector of tropical fish may become the devoted gardener. Careers may change—the determined salesperson may become a determined social worker. Relationships may change—the hostile spouse may start over with a new partner. But most people recognize their traits as just who they are.

The consistency of specific behaviors from one situation to the next is another matter. People are not always predictable. What relationship would you expect to find between being conscientious on one occasion (say, showing up for class on time) and being conscientious on another occasion (say, avoiding unhealthy foods)? If you’ve noticed how outgoing you are in some situations and how reserved you are in others, perhaps you said, “Very little.” That’s what researchers have found—only a small correlation (Mischel, 1968, 2004; Sherman et al., 2015). This inconsistency makes personality traits weak predictors of behaviors. Personality traits predict a person’s behavior across many different situations. They do not neatly predict a person’s behavior in any one specific situation (Mischel, 1968, 1984; Mischel & Shoda, 1995).

If we remember such results, we will be more careful about labeling other people (Mischel, 1968, 2004). We will recognize how difficult it is to predict whether someone is likely to violate parole, commit suicide, or be an effective employee. Years in advance, science can tell us the distance of the Earth from the Sun for any given date. A day in advance, meteorologists can often predict the weather. Yet psychologists have not yet solved the riddle of how you will feel and act tomorrow, or even a few hours from now.

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Does this mean that psychological science has nothing meaningful to say about personality traits? No! Remember that traits do a good job at predicting people’s average behavior (outgoingness, happiness, carelessness) over many situations (Epstein, 1983a,b).

Even when we try to restrain them, our traits may assert themselves. During my [DM] noontime pickup basketball games with friends, I keep vowing to cut back on my jabbering and joking. But without fail, the irrepressible chatterbox reoccupies my body moments later. I [ND] have a similar experience each time I try to stay quiet when riding in taxis, but somehow always end up chatting!

Our personality traits lurk in some unexpected places.

In unfamiliar, formal situations—perhaps as a guest in the home of a person from another culture—our traits remain hidden as we carefully attend to social cues. In familiar, informal situations—just hanging out with friends—we feel more relaxed, and our traits emerge (Buss, 1989). In these informal situations, our expressive styles—our animation, manner of speaking, and gestures—are impressively consistent. Viewing “thin slices” of someone’s behavior—such as seeing a photo for a mere fraction of a second or seeing three different 2-second video clips of a teacher in action—can tell us a lot about the person’s basic personality traits (Ambady, 2010; Rule et al., 2009).

To sum up, we can say that the immediate situation powerfully influences our behavior, especially when the situation makes clear demands (Cooper & Withey, 2009). We can better predict drivers’ behavior at traffic lights from knowing the color of the lights than from knowing the drivers’ personalities. Averaging our behavior across many occasions does, however, reveal distinct personality traits. Traits exist, and they leave tracks in our lives. We differ. And our differences matter.