Explaining Personality: Biological Approaches and Trait Theories

Learning Objectives

  • Explain biological approaches to understanding personality, including the findings of the Minnesota Study of Twins Reared Apart, heritability, and temperament
  • Discuss the early trait theories of Cattell and Eysenck
  • Describe the Big Five factors and categorize someone who is high and low on each of the five traits
  • Discuss personality differences of people from collectivist and individualist cultures and compare the cultural-comparative approach, the indigenous approach, and the combined approach to studying personality

Biological Approaches

How much of our personality is in-born and biological, and how much is influenced by the environment and culture we are raised in? Psychologists who favor the biological approach believe that inherited predispositions as well as physiological processes can be used to explain differences in our personalities (Burger, 2008).

In the field of behavioral genetics, the Minnesota Study of Twins Reared Apart—a well-known study of the genetic basis for personality—conducted research with twins from 1979 to 1999. In studying 350 pairs of twins, including pairs of identical and fraternal twins reared together and apart, researchers found that identical twins, whether raised together or apart, have very similar personalities (Bouchard, 1994; Bouchard, Lykken, McGue, Segal, & Tellegen, 1990; Segal, 2012). These findings suggest the heritability of some personality traits. Heritability refers to the proportion of difference among people that is attributed to genetics. Some of the traits that the study reported as having more than a 0.50 heritability ratio include leadership, obedience to authority, a sense of well-being, alienation, resistance to stress, and fearfulness. The implication is that some aspects of our personalities are largely controlled by genetics; however, it’s important to point out that traits are not determined by a single gene, but by a combination of many genes, as well as by epigenetic factors that control whether the genes are expressed.

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Most contemporary psychologists believe temperament has a biological basis due to its appearance very early in our lives (Rothbart, 2011). As you learned when you studied lifespan development, Thomas and Chess (1977) found that babies could be categorized into one of three temperaments: easy, difficult, or slow to warm up. However, environmental factors (family interactions, for example) and maturation can affect the ways in which children’s personalities are expressed (Carter et al., 2008).

Research suggests that there are two dimensions of our temperament that are important parts of our adult personality—reactivity and self-regulation (Rothbart, Ahadi, & Evans, 2000). Reactivity refers to how we respond to new or challenging environmental stimuli; self-regulation refers to our ability to control that response (Rothbart & Derryberry, 1981; Rothbart, Sheese, Rueda, & Posner, 2011). For example, one person may immediately respond to new stimuli with a high level of anxiety, while another barely notices it.

Connect the Concepts: Body Type and Temperament

Is there an association between your body type and your temperament? The constitutional perspective, which examines the relationship between the structure of the human body and behavior, seeks to answer this question (Genovese, 2008). The first comprehensive system of constitutional psychology was proposed by American psychologist William H. Sheldon (1940, 1942). He believed that your body type can be linked to your personality. Sheldon’s life’s work was spent observing human bodies and temperaments. Based on his observations and interviews of hundreds of people, he proposed three body/personality types, which he called somatotypes.

The three somatotypes are ectomorphs, endomorphs, and mesomorphs (Figure 1). Ectomorphs are thin with a small bone structure and very little fat on their bodies. According to Sheldon, the ectomorph personality is anxious, self-conscious, artistic, thoughtful, quiet, and private. They enjoy intellectual stimulation and feel uncomfortable in social situations. Actors Adrien Brody and Nicole Kidman would be characterized as ectomorphs. Endomorphs are the opposite of ectomorphs. Endomorphs have narrow shoulders and wide hips, and carry extra fat on their round bodies. Sheldon described endomorphs as being relaxed, comfortable, good-humored, even-tempered, sociable, and tolerant. Endomorphs enjoy affection and detest disapproval. Queen Latifah and Jack Black would be considered endomorphs. The third somatotype is the mesomorph. This body type falls between the ectomorph and the endomorph. Mesomorphs have large bone structure, well-defined muscles, broad shoulders, narrow waists, and attractive, strong bodies. According to Sheldon, mesomorphs are adventurous, assertive, competitive, and fearless. They are curious and enjoy trying new things, but can also be obnoxious and aggressive. Channing Tatum and Scarlett Johannson would likely be mesomorphs.

The outlines of three human somatotypes are shown. The first is labeled, “Endomorph,” the second is labeled “Mesomorph,” and the third is labeled “Ectomorph.” Endomorphs are slightly larger than mesomorphs, and ectomorphs are slightly smaller than mesomorphs.

Figure 1. Sheldon proposed three somatotypes: endomorphs, mesomorphs, and ectomorphs. Do you think Sheldon’s ideas about somatotypes are generally accurate about most people?

Sheldon (1949) also conducted further research into somatotypes and criminality. He measured the physical proportions of hundreds of juvenile delinquent boys in comparison to male college students, and found that problem youth were primarily mesomorphs. Why might this be? Perhaps it’s because they are quick to anger and don’t have the restraint demonstrated by ectomorphs. Maybe it’s because a person with a mesomorphic body type reflects high levels of testosterone, which may lead to more aggressive behavior. Can you think of other explanations for Sheldon’s findings?

Sheldon’s method of somatotyping is not without criticism, as it has been considered largely subjective (Carter & Heath, 1990; Cortés & Gatti, 1972; Parnell, 1958). More systematic and controlled research methods did not support his findings (Eysenck, 1970). Consequently, it’s not uncommon to see his theory labeled as pseudoscience, much like Gall’s theory of phrenology (Rafter, 2007; Rosenbaum, 1995). However, studies involving correlations between somatotype, temperament, and children’s school performance (Sanford et al., 1943; Parnell); somatotype and performance of pilots during wartime (Damon, 1955); and somatotype and temperament (Peterson, Liivamagi, & Koskel, 2006) did support his theory.

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Think It Over

  • Research suggests that many of our personality characteristics have a genetic component. What traits do you think you inherited from your parents? Provide examples. How might modeling (environment) influenced your characteristics as well?

Trait Theories

Trait theorists believe personality can be understood via the approach that all people have certain traits, or characteristic ways of behaving. Do you tend to be sociable or shy? Passive or aggressive? Optimistic or pessimistic? Moody or even-tempered? Early trait theorists tried to describe all human personality traits. For example, one trait theorist, Gordon Allport (Allport & Odbert, 1936), found 4,500 words in the English language that could describe people. He organized these personality traits into three categories: cardinal traits, central traits, and secondary traits. A cardinal trait is one that dominates your entire personality, and hence your life—such as Ebenezer Scrooge’s greed and Mother Theresa’s altruism. Cardinal traits are not very common: Few people have personalities dominated by a single trait. Instead, our personalities typically are composed of multiple traits. Central traits are those that make up our personalities (such as loyal, kind, agreeable, friendly, sneaky, wild, and grouchy). Secondary traits are those that are not quite as obvious or as consistent as central traits. They are present under specific circumstances and include preferences and attitudes. For example, one person gets angry when people try to tickle him; another can only sleep on the left side of the bed; and yet another always orders her salad dressing on the side. And you—although not normally an anxious person—feel nervous before making a speech in front of your English class.

In an effort to make the list of traits more manageable, Raymond Cattell (1946, 1957) narrowed down the list to about 171 traits. However, saying that a trait is either present or absent does not accurately reflect a person’s uniqueness, because all of our personalities are actually made up of the same traits; we differ only in the degree to which each trait is expressed. Cattell (1957) identified 16 factors or dimensions of personality: warmth, reasoning, emotional stability, dominance, liveliness, rule-consciousness, social boldness, sensitivity, vigilance, abstractedness, privateness, apprehension, openness to change, self-reliance, perfectionism, and tension (Table 1). He developed a personality assessment based on these 16 factors, called the 16PF. Instead of a trait being present or absent, each dimension is scored over a continuum, from high to low. For example, your level of warmth describes how warm, caring, and nice to others you are. If you score low on this index, you tend to be more distant and cold. A high score on this index signifies you are supportive and comforting.

Table 1. Personality Factors Measured by the 16PF Questionnaire
Factor Low Score High Score
Warmth Reserved, detached Outgoing, supportive
Intellect Concrete thinker Analytical
Emotional stability Moody, irritable Stable, calm
Aggressiveness Docile, submissive Controlling, dominant
Liveliness Somber, prudent Adventurous, spontaneous
Dutifulness Unreliable Conscientious
Social assertiveness Shy, restrained Uninhibited, bold
Sensitivity Tough-minded Sensitive, caring
Paranoia Trusting Suspicious
Abstractness Conventional Imaginative
Introversion Open, straightforward Private, shrewd
Anxiety Confident Apprehensive
Openmindedness Closeminded, traditional Curious, experimental
Independence Outgoing, social Self-sufficient
Perfectionism Disorganized, casual Organized, precise
Tension Relaxed Stressed

Link to Learning

Follow this link to an assessment based on Cattell’s 16PF questionnaire to see which personality traits dominate your personality.

A photograph shows Hans and Sybil Eysenck together.”

Figure 2. Hans and Sybil Eysenck believed that our personality traits are influenced by our genetic inheritance. (credit: “Sirswindon”/Wikimedia Commons)

Psychologists Hans and Sybil Eysenck were personality theorists (Figure 2) who focused on temperament, the inborn, genetically based personality differences that you studied earlier in the module. They believed personality is largely governed by biology. The Eysencks (Eysenck, 1990, 1992; Eysenck & Eysenck, 1963) viewed people as having two specific personality dimensions: extroversion/introversion and neuroticism/stability.

According to their theory, people high on the trait of extroversion are sociable and outgoing, and readily connect with others, whereas people high on the trait of introversion have a higher need to be alone, engage in solitary behaviors, and limit their interactions with others. In the neuroticism/stability dimension, people high on neuroticism tend to be anxious; they tend to have an overactive sympathetic nervous system and, even with low stress, their bodies and emotional state tend to go into a flight-or-fight reaction. In contrast, people high on stability tend to need more stimulation to activate their flight-or-fight reaction and are considered more emotionally stable. Based on these two dimensions, the Eysencks’ theory divides people into four quadrants. These quadrants are sometimes compared with the four temperaments described by the Greeks: melancholic, choleric, phlegmatic, and sanguine (Figure 3).

A circle is divided vertically and horizontally into four sections by lines with arrows at the ends. Clockwise from the top, the arrows are labeled “Unstable Emotions (Neurotic),” “Extroverted Personality,” “Stable Emotions,” and “Introverted Personality.” The arcs around the perimeter of the circle, clockwise beginning with the top right segment are labeled “Choleric,” “Sanguine,” “Phlegmatic,” and “Melancholic.” The sections inside each arc contain descriptive words. Inside the Choleric arc are the words “touchy, restless, aggressive, excitable, impulsive, and active.” Inside the Sanguine arc are the words “sociable, talkative, responsive, easygoing, lively, and carefree.” Inside the Phlegmatic arc are the words “passive, thoughtful, peaceful, controlled, reliable, and calm.” Inside the Melancholic arc are the words “moody, anxious, rigid, pessimistic, unsociable, and quiet.”

Figure 3. The Eysencks described two factors to account for variations in our personalities: extroversion/introversion and emotional stability/instability.

Later, the Eysencks added a third dimension: psychoticism versus superego control (Eysenck, Eysenck & Barrett, 1985). In this dimension, people who are high on psychoticism tend to be independent thinkers, cold, nonconformists, impulsive, antisocial, and hostile, whereas people who are high on superego control tend to have high impulse control—they are more altruistic, empathetic, cooperative, and conventional (Eysenck, Eysenck & Barrett, 1985).

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The Big 5

While Cattell’s 16 factors may be too broad, the Eysenck’s two-factor system has been criticized for being too narrow. Another personality theory, called the Five Factor Model, effectively hits a middle ground, with its five factors referred to as the Big Five personality traits. It is the most popular theory in personality psychology today and the most accurate approximation of the basic trait dimensions (Funder, 2001). The five traits are openness to experience, conscientiousness, extroversion, agreeableness, and neuroticism (Figure 4). A helpful way to remember the traits is by using the mnemonic OCEAN.

In the Five Factor Model, each person has each trait, but they occur along a spectrum. Openness to experience is characterized by imagination, feelings, actions, and ideas. People who score high on this trait tend to be curious and have a wide range of interests. Conscientiousness is characterized by competence, self-discipline, thoughtfulness, and achievement-striving (goal-directed behavior). People who score high on this trait are hardworking and dependable. Numerous studies have found a positive correlation between conscientiousness and academic success (Akomolafe, 2013; Chamorro-Premuzic & Furnham, 2008; Conrad & Patry, 2012; Noftle & Robins, 2007; Wagerman & Funder, 2007). Extroversion is characterized by sociability, assertiveness, excitement-seeking, and emotional expression. People who score high on this trait are usually described as outgoing and warm. Not surprisingly, people who score high on both extroversion and openness are more likely to participate in adventure and risky sports due to their curious and excitement-seeking nature (Tok, 2011). The fourth trait is agreeableness, which is the tendency to be pleasant, cooperative, trustworthy, and good-natured. People who score low on agreeableness tend to be described as rude and uncooperative, yet one recent study reported that men who scored low on this trait actually earned more money than men who were considered more agreeable (Judge, Livingston, & Hurst, 2012). The last of the Big Five traits is neuroticism, which is the tendency to experience negative emotions. People high on neuroticism tend to experience emotional instability and are characterized as angry, impulsive, and hostile. Watson and Clark (1984) found that people reporting high levels of neuroticism also tend to report feeling anxious and unhappy. In contrast, people who score low in neuroticism tend to be calm and even-tempered.

A diagram includes five vertically stacked arrows, which point to the left and right. A dimension's first letter, name, and description are included inside of each arrow. A box to the left of each arrow includes traits associated with a low score for that arrow's dimension. A box to the right of each arrow includes traits associated with a high score for that arrow's dimension. The top arrow includes the trait “openness,” which is described with the words, “imagination,” “feelings,” “actions,” and “ideas.” The box to the left of that arrow includes the words, “practical,” “conventional,” and “prefers routine,” while the box to the right of that arrow includes the words, “curious,” “wide range of interests,” and “independent.” The next arrow includes the trait “conscientiousness,” which is described with the words, “competence,” “self-discipline,” “thoughtfulness,” and “goal-driven.” The box to the left of that arrow includes the words, “impulsive,” “careless,” and “disorganized,” while the box to the right of that arrow includes the words, “hardworking,” “dependable,” and “organized.” The next arrow includes the trait “extroversion,” which is described with the words, “sociability,” “assertiveness,” and “emotional expression.” The box to the left of that arrow includes the words, “quiet,” “reserved,” and “withdrawn,” while the box to the right of that arrow includes the words, “outgoing,” “warm,” and “seeks adventure.” The next arrow includes the trait “agreeableness,” which is described with the words, “cooperative,” “trustworthy,” and “good-natured.” The box to the left of that arrow includes the words, “critical,” “uncooperative,” and “suspicious,” while the box to the right of that arrow includes the words, “helpful,” “trusting,” and “empathetic.” The next arrow includes the trait “neuroticism,” which is described as “tendency toward unstable emotions.” The box to the left of that arrow includes the words, “calm,” “even-tempered,” and “secure,” while the box to the right of that arrow includes the words, “anxious,” “unhappy,” and “prone to negative emotions.”

Figure 4. In the Five Factor Model, each person has five traits, each scored on a continuum from high to low. In the center column, notice that the first letter of each trait spells the mnemonic OCEAN.

The Big Five personality factors each represent a range between two extremes. In reality, most of us tend to lie somewhere midway along the continuum of each factor, rather than at polar ends. It’s important to note that the Big Five traits are relatively stable over our lifespan, with some tendency for the traits to increase or decrease slightly. Researchers have found that conscientiousness increases through young adulthood into middle age, as we become better able to manage our personal relationships and careers (Donnellan & Lucas, 2008). Agreeableness also increases with age, peaking between 50 to 70 years (Terracciano, McCrae, Brant, & Costa, 2005). Neuroticism and extroversion tend to decline slightly with age (Donnellan & Lucas; Terracciano et al.). Additionally, The Big Five traits have been shown to exist across ethnicities, cultures, and ages, and may have substantial biological and genetic components (Jang, Livesley, & Vernon, 1996; Jang et al., 2006; McCrae & Costa, 1997; Schmitt et al., 2007).

Link to Learning

To find out about your personality and where you fall on the Big Five traits, follow this link to take the Big Five personality test.

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Think It Over

  • Review the Big Five personality traits shown in Figure 4. On which areas would you expect you’d score high? In which areas does the low score more accurately describe you?

Cultural Understandings of Personality

As you have learned in this module, personality is shaped by both genetic and environmental factors. The culture in which you live is one of the most important environmental factors that shapes your personality (Triandis & Suh, 2002). The term culture refers to all of the beliefs, customs, art, and traditions of a particular society. Culture is transmitted to people through language as well as through the modeling of culturally acceptable and nonacceptable behaviors that are either rewarded or punished (Triandis & Suh, 2002). With these ideas in mind, personality psychologists have become interested in the role of culture in understanding personality. They ask whether personality traits are the same across cultures or if there are variations. It appears that there are both universal and culture-specific aspects that account for variation in people’s personalities.

Why might it be important to consider cultural influences on personality? Western ideas about personality may not be applicable to other cultures (Benet-Martinez & Oishi, 2008). In fact, there is evidence that the strength of personality traits varies across cultures. Let’s take a look at some of the Big Five factors (conscientiousness, neuroticism, openness, and extroversion) across cultures. As you will learn when you study social psychology, Asian cultures are more collectivist, and people in these cultures tend to be less extroverted. People in Central and South American cultures tend to score higher on openness to experience, whereas Europeans score higher on neuroticism (Benet-Martinez & Karakitapoglu-Aygun, 2003).

According to this study, there also seem to be regional personality differences within the United States (Figure 5). Researchers analyzed responses from over 1.5 million individuals in the United States and found that there are three distinct regional personality clusters: Cluster 1, which is in the Upper Midwest and Deep South, is dominated by people who fall into the “friendly and conventional” personality; Cluster 2, which includes the West, is dominated by people who are more relaxed, emotionally stable, calm, and creative; and Cluster 3, which includes the Northeast, has more people who are stressed, irritable, and depressed. People who live in Clusters 2 and 3 are also generally more open (Rentfrow et al., 2013).

A map of the United States is shown. Above it is the label “Personality Clusters in the Continental United States.” Below it is a legend which defines areas in the map as either, “Cluster 1: friendly, conventional;” “Cluster 2: relaxed, creative;” or “Cluster 3: temperamental, uninhibited.” Cluster 1occurs mainly in the center of the country. Cluster 2 occurs mainly on the west side of the country. Cluster 3 occurs mainly in the North-East region of the country and also in Texas. These are generalizations; there are several states which are comprised of a combination of two different clusters.

Figure 5. Researchers found three distinct regional personality clusters in the United States. People tend to be friendly and conventional in the Upper Midwest and Deep South; relaxed, emotionally stable, and creative in the West; and stressed, irritable, and depressed in the Northeast (Rentfrow et al., 2013).

One explanation for the regional differences is selective migration (Rentfrow et al., 2013). Selective migration is the concept that people choose to move to places that are compatible with their personalities and needs. For example, a person high on the agreeable scale would likely want to live near family and friends, and would choose to settle or remain in such an area. In contrast, someone high on openness would prefer to settle in a place that is recognized as diverse and innovative (such as California).

Personality in Individualist and Collectivist Cultures

Individualist cultures and collectivist cultures place emphasis on different basic values. People who live in individualist cultures tend to believe that independence, competition, and personal achievement are important. Individuals in Western nations such as the United States, England, and Australia score high on individualism (Oyserman, Coon, & Kemmelmier, 2002). People who live in collectivist cultures value social harmony, respectfulness, and group needs over individual needs. Individuals who live in countries in Asia, Africa, and South America score high on collectivism (Hofstede, 2001; Triandis, 1995). These values influence personality. For example, Yang (2006) found that people in individualist cultures displayed more personally oriented personality traits, whereas people in collectivist cultures displayed more socially oriented personality traits.

Approaches to Studying Personality in a Cultural Context

There are three approaches that can be used to study personality in a cultural context, the cultural-comparative approach; the indigenous approach; and the combined approach, which incorporates elements of both views. Since ideas about personality have a Western basis, the cultural-comparative approach seeks to test Western ideas about personality in other cultures to determine whether they can be generalized and if they have cultural validity (Cheung van de Vijver, & Leong, 2011). For example, recall from the previous section on the trait perspective that researchers used the cultural-comparative approach to test the universality of McCrae and Costa’s Five Factor Model. They found applicability in numerous cultures around the world, with the Big Five traits being stable in many cultures (McCrae & Costa, 1997; McCrae et al., 2005). The indigenous approach came about in reaction to the dominance of Western approaches to the study of personality in non-Western settings (Cheung et al., 2011). Because Western-based personality assessments cannot fully capture the personality constructs of other cultures, the indigenous model has led to the development of personality assessment instruments that are based on constructs relevant to the culture being studied (Cheung et al., 2011). The third approach to cross-cultural studies of personality is the combined approach, which serves as a bridge between Western and indigenous psychology as a way of understanding both universal and cultural variations in personality (Cheung et al., 2011).

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Think It Over

  • According to the work of Rentfrow and colleagues, personalities are not randomly distributed. Instead they fit into distinct geographic clusters. Based on where you live, do you agree or disagree with the traits associated with yourself and the residents of your area of the country? Why or why not?


culture: all of the beliefs, customs, art, and traditions of a particular society
Five Factor Model: theory that personality is composed of five factors or traits, including openness, conscientiousness, extroversion, agreeableness, and neuroticism
heritability: proportion of difference among people that is attributed to genetics
selective migration: concept that people choose to move to places that are compatible with their personalities and needs
temperament: how a person reacts to the world, including their activity level, starting when they are very young
traits: characteristic ways of behaving