Coffee / Pixabay
Source: Coffee / Pixabay

So this winter I’m teaching an online course in personality psychology. I love teaching this class for various reasons. For one, it always underscores for me how important it is to appreciate the fact that each of us approaches the world in our own unique way. To a large extent, that is what personality psychology is all about.

While the field of personality psychology includes many different kinds of concepts (see Larsen & Buss, 2017), a core focus of this field is on the basic trait dimensions that underlie how we (a) are consistent in our own behavior across time and across contexts as well as (b) how we reliably differ from others in our behavioral tendencies.

Based on decades of extensive and multi-faceted research, personality psychologists have come to define the core trait dimensions that importantly define who we are. Below is, from my perspective as a scholar in this field, a brief summary of nine trait dimensions that powerfully predict human behavior across the lifespan.

One important thing to note before progressing: Each of these trait dimensions is, in fact, just that—a dimension with extreme scores on either end. Thus, the dimension of “extraversion” has scores on one end corresponding to very extraverted individuals and scores on the other end corresponding to very introverted individuals. Further, these dimensions are generally “normally distributed”—meaning (roughly) that the majority of people score as somewhere near average (and as not extreme). This is an important detail to keep in mind in considering the nature of human personality traits.

The Big Five Personality Trait Dimensions

Based on a broad array of studies across nearly a century of research, personality psychologists have come to find that nearly all personality traits map onto one of the following five dimensions. These “Big Five” trait dimensions, thus, encompass nearly the entirety of human personality structure—across time and culture, in fact (see John, 1990).

The Big Five are as follows:

  • Extraversion-Introversion. This dimension (usually referred to as just “extraversion”) speaks to how outgoing someone is - and how comfortable someone is in social settings. People who are extreme extroverts have no problem standing up on stage and speaking. Those who are extreme introverts would rather be caught dead. And, as with all of the dimensions described here, most of us are somewhere in the middle.
  • Neuroticism-Emotional Stability. This dimension (usually referred to as just “neuroticism”) corresponds to how emotionally volatile someone is. Someone who is highly neurotic is prone toward frequent changes in mood and is prone toward negative affect (bad feelings). Someone who is very emotionally stable is cool as a cucumber. Someone who is highly neurotic would freak out when a siren is heard in the neighborhood. Someone who is low in neuroticism wouldn’t even notice that same siren.
  • Agreeableness-Disagreeableness. This dimension (usually referred to as just “agreeableness”) corresponds to how easy going and friendly someone is. Someone who is very agreeable tends to get along with just about anyone while someone who is highly disagreeable just argues and argues. Someone who is highly agreeable is the kind of person who says “I don’t care where we go out to eat - it’s all good” while someone who is highly disagreeable would be more like “I don’t like that place! Or THAT place! OR THAT PLACE!!! ...”
  • Conscientiousness-Disorganized. This dimension (usually referred to as just “conscientiousness”) corresponds to how organized and on-the-ball someone is. Someone who is highly conscientious is always reliable, always makes deadlines, and keeps his or her workspace straight as an arrow. Someone low in conscientiousness is always late, rarely makes deadlines, and does not keep his or her physical space in a fully organized manner. Someone who is high in conscientiousness would make a great accountant. Someone low in conscientiousness might be the kind of person who is always losing a $20 bill (I know I had it somewhere in this bag! …”).
  • Openness-Closed-minded. This dimension (usually referred to as just “openness” or “openness to experience”) corresponds to being open-minded. Someone who is high on openness is open to new ideas, new people, and new ways of doing things. Someone who is low in this dimension is very closed-minded and does not want to hear any new ideas. Someone who is open-minded may be excited to go to an art museum to experience a fancy, cutting-edge new art genre. Someone who is closed-minded would rather sit in the car for the duration of the museum visit.

The Dimensions of the Dark Triad

While the Big Five are often described as all-encompassing, a good deal of recent research (see, for example, Jonason et al., 2013) has found that another set of trait dimensions, known collectively as the “dark triad,” predicts much in the way of behavioral outcomes beyond what is explained by the Big Five alone. These three dimensions, which often are found to be predictive of one another (i.e., inter-correlated) are narcissism, psychopathy, and Machiavellianism.

  • Narcissism-Selflessness. This dimension (referred to as just “narcissism”) corresponds to how self-absorbed someone is. Someone who is high in narcissism spends a disproportionate amount of time thinking about oneself - with oneself as the center of pretty much everything. Someone low in this dimension does not have a strong focus on self and does not see him or herself as the focus of any particular situation. Someone high in narcissism might post 18 selfies a day on Facebook. Someone low on this dimension might not know how to put the iPhone into selfie mode.
  • Psychopathy-Empathic. This dimension (referred to as just “psychopathic”) corresponds to an approach to others that is fully uncaring. Someone who is high in psychopathy does not feel for others or care about their welfare much at all, while someone who is low in this trait cares for others genuinely and cares for them a great deal. Someone who is psychopathic might feel no emotion whatsoever while watching the scene when Bambi’s mother dies. Someone who is more on the empathic side of this dimension might have cried when first watching that scene - and might feel bad about it still even years later.
  • Machiavellianism-Scrupulous. This dimension (referred to as just “Machiavellianism”) corresponds to an approach to social life in which others are used as pawns for one’s own personal gain. People who are high in Machiavellianism will only do the right thing to others to the extent that doing the right thing is beneficial for oneself. Someone low in this dimension, on the other hand, has a strong moral compass and will strive to do the right thing regardless of a benefit to oneself. A boss who is high in Machiavellianism might give special favors to an employee who provides him or her with inside information on others in the workplace. A boss who is low in this dimension would make sure to treat all employees equally, regardless of just about anything.

The Life History Dimension

A final foundational trait dimension in modern personality psychology is that of life history strategy (see Figueredo et al., 2008). Rooted in an evolutionary approach to life, this dimension has two extreme ends - each of which being an optimal life strategy under certain circumstances. These extremes of life history strategy, as described below, are “slow life history strategy” and “fast life history strategy.”

  • Slow life history strategy / Fast life history strategy. This dimension (usually referred to as the non-directional  “life history strategy”) corresponds to whether someone takes an approach to life that seems to anticipate a highly secure and stable environment versus an approach that seems to anticipate a highly insecure and unstable environment. Someone who seems to anticipate a stable environment (i.e., someone who has a slow life history strategy) will take an approach to life that is slow, taking steps to invest much in the future. Someone who seems to anticipate an unstable environment (i.e., someone who has a fast life history strategy) will take an approach to life that focuses more on the here and now, as if expecting that life might end at any point. Someone with a slow life history strategy might wait to get married until the end of graduate school—and then start thinking about having kids. Someone with a fast life history strategy might have three kids during the teenage years - and not think about getting married at any point.

Bottom Line

One of the core ideas in personality psychology pertains to personality traits—ways that we are consistent within ourselves across lifespan and are, concurrently, reliably different from others. Variability in personality traits is one of the core ways that human uniqueness is expressed. While there are many important traits that characterize who we are, the nine described here comprise foundational trait dimensions that have been shown to powerfully predict human behavior. Want to understand who someone is? You might be wise to think about where that person resides on the basic trait dimensions described here.


Figueredo , A. J. , Brumbach , B. H. , Jones , D. N. , Sefcek , J. A. , Vasquez , G. , & Jacobs , W. J. ( 2008 ). Ecological constraints on mating tactics. In G. Geher & G. Miller (Eds.), Mating intelligence: Sex, relationships, and the mind’s reproductive system (pp. 337–365). Mahwah, NJ: Lawrence Erlbaum.

John, O. P. (1990). The "Big Five" factor taxonomy: Dimensions of personality in the natural language and in questionnaires. In L. A. Pervin (Ed.), Handbook of personality: Theory and research (pp. 66-100). New York: Guilford.

Jonason, P. K., Kaufman, S. B., Webster, G. D, & Geher, G. (2013). What lies beneath the Dark Triad Dirty Dozen: Varied relations with the Big Five. Individual Differences Research, 11, 81-90.

Larsen, R., & Buss, D. M. (2017). Personality Psychology. New York: McGraw Hill.

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