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Theories of Personality

How different theories explain the development of personality and individual differences.

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Theories of Personality

How can human personality be defined? What traits are our personalities composed of, and what genetic or environmental factors cause each individual’s personality to be different?

Personality Theories

Personality, and the factors that influence it, have been the focus of study since Ancient Greece. Early theories attributed differences in personality to the abundance or absence of  four types of bodily fluid known as humors.

In recent decades, psychologists have proposed a number of further theories explaining personality. Some, such as Friedman and Rosenman, focus on an individual’s observable behavior. Other theories, such as the Five Factor Model, take a trait theory approach, seeking to understand personality in terms of specific attitudes and types of behavior.

In this article, we look at the theories and ‘models’ which have shaped our understanding of human personality.

Early Theories

Even prior to the development of modern psychology, the influences that shape individuals’ personality traits has intrigued humankind for generations.

In Ancient Greece, four personality types or ‘temperaments’ were recognised: choleric, melancholic, phlegmatic and sanguine. A person’s personality could possess varying degrees of each trait.

Hippocrates (c. 460 - c. 370 B.C.E), a doctor who is considered to be the father of modern medicine, believed that variations in temperament were caused by excesses or deficiencies of fluids in the body. This theory - humorism - emphasizes the significance of four humors, which along with the four seasons and elements, were associated with a specific temperament:

Temperament Humor Element Season






Yellow Bile




Black Bile







Whilst this antiquated attempt at understanding the causes of personality differences today seems over-simplistic, the four temperaments recognize the influence of biological factors on human personality and behavior. Whilst the four humors may not determine personality, subsequent theories provide genetic and neurochemical explanations of human behavior.   

Moreover, some modern theories of personality, such as the five-factor model, recognize traits which to some extent resemble the temperaments of Ancient Greece. Introversion, for instance, shares many aspects of the melancholic temperament.

Psychodynamic Approach

Are we conscious of our own personality traits, or is our behavior determined by subconscious drives?

Austrian neurologist Sigmund Freud (1856-1939) developed a psychodynamic theory of the human psyche, which focussed on the influence of key drives on behavior that a person would be otherwise unaware of.

Sigmund Freud
Sigmund Freud

Freud believed that the psyche was controlled by three competing components: the id, ego and super ego.

The id follows the pleasure principle, which drives a person to behave in a way which will maximize the potential for reward. However, it disregards the potentially detrimental effect that one’s behavior may have on other people.

The id dominates behavior in early childhood, but is soon challenged by the ego. The ego follows the reality principle, which acknowledges that in reality, external limitations apply to the way in which a person can behave.

As a child grows older, the super ego develops, and is responsible for their conscience. According to Freud, it causes a person to recognize the consequences of their actions and to experience guilt or shame as a result of their behavior.

Freud believed that the competing interests of the three aspects of the psyche governed a person’s conscious thoughts and behavior. Whilst this psychodynamic approach was influential amongst psychologists and psychoanalysts, its deterministic approach to personality has been criticised. It focusses on the invisible influence of unconscious drives, and as a result, it is impossible to either prove or falsify Freud’s theory. This model of the psyche also fails to account for free will and the often unpredictable nature of human behavior.

Trait Theory

Trait theory aims to understand personality by categorizing attitudes and specific types of behavior into ‘traits’. These traits describe a tendency of a person to think, feel or behave in a particular way.

Trait theory takes a lexical approach to personality, supposing that languages acquire terms to describe personality traits, so that people may discuss them. It assumes that dimensions of personality can be understood using existing terms - often words or short phrases.

The measurement of personality traits tends to be based on a continuum, with individuals’ scores ranging from low to high. For instance, extraversion-introversion and neuroticism-emotional instability.

Early research into personality traits was undertaken by Gordon Allport and Henry Odbert. In 1936, they compiled an extensive list of personality traits, comprised of over 4,500 English language terms derived from Webster’s New International Dictionary.

Subsequent research by psychologist Raymond Cattell used factor analysis to produce a more concise inventory of personality traits, each of which encompassed many of the attributes identified by Allport and Odbert. Cattell identified 16 key personality traits and developed the Sixteen Personality Factor Questionnaire (16PF), an instrument that could be used to measure these traits.

In recent decades, five broad personality traits - the ‘Big Five’ factors - have been identified, each covering numerous secondary ‘facets’ (see below).

Eysenck’s PEN Model

Whilst working at Maudsley Hospital in London, German-born psychologist Hans Eysenck (1916-1997) developed a set of questions to assess the personalities of the soldiers being treated there. Using factor analysis, Eysenck found that many of the soldiers’ responses were related to the answers given to other questions (Eysenck, 1947).

The plethora of specific personality traits that he observed appeared to be related, and so Eysenck proposed two key traits, which each encompassed many subordinate traits.

Initially, he produced a two-axis measure of personality using extraversion-introversion and neuroticism-emotional stability. Individuals’ personalities could be assessed according to these traits, with most falling towards the center of each scale.

Hans’ wife, Sybil Eysenck, was also a psychologist studying personality, and she proposed the inclusion of a third measure, psychoticism. Together, these three factors form the PEN model of personality (Eysenck and Eysenck, 1976).

Hans and Sybil developed the Eysenck Personality Questionnaire (EPQ) as an instrument to measure these three personality traits.

Controversially Eysenck believed that biological factors could account for much of the variation in these three personality traits, and that the hereditary influence of genes also helps to determine an individual’s behavior.

For example, he suggested that extraversion was caused by a need for cortical arousal in the ascending reticular activating system (ARAS) region of the brain-stem. Whilst extraverts crave such arousal from external stimuli, introverts seek to avoid it, resulting in less outgoing behavior.

Gray’s Biopsychological Model

British psychologist Jeffrey Alan Grey (1934-2004) studied under Hans Eysenck at the Institute of Psychiatry in London. He further developed the model of personality originally proposed by Eysenck, proposing a biopsychological theory (Gray, 1970).

Gray believed that behavior is influenced by two systems. The first, described as the behavioral activation system (BIS), influences behavior with a view to obtaining pleasure and other rewards. This may, for example lead a person to eat an unhealthily cake, which proves rewarding in the short-term but can has a detrimental effect in the longer term.

A second system, the behavioral inhibition system (BAS), motivates a person to avoid potential punishments. This system can lead a person to be cautious when faced with risk.

According to Gray, neuroticism, which was a focus of Eysenck’s PEN model, could be explained in terms of these two systems.

The behavioral inhibition system of a person with a high level of neuroticism was likely be more active, whereas the behavior of a person with low level of the trait would be dominated by the behavior activation system.

Five-Factor Model

The five-factor model (FFM) was developed by numerous researchers, including personality psychologists Robert McCrae and Paul Costa. In line with trait theory, which analyses personality differences in terms of individual attitudes and patterns of behaviors, the Five-Factor Model focuses on five broad measures of personality.

  • Openness to Experience
    A willingness to try new activities, experience different ways of life and to embrace unconventional ideas.
  • Conscientiousness
    A tendency to be conscientious of one’s own behavior and the consequences of one’s actions. Conscientious people like to be well-organized, punctual and are goal-oriented in their behavior.
  • Extraversion
    Extraverts are lively, talkative and outgoing. They are confident socialisers and enjoy meeting new people. Low extraversion, or introversion, is characterised by quietness and often shy behavior.
  • Agreeableness
    Agreeable individuals are cooperative, altruistic and helpful. They are perceived as being ‘warm’ in social situations. Low agreeableness results in selfish behavior and increased levels of suspicion or distrust of others.
  • Neuroticism
    People experiencing high level of neuroticism tend to worry and experience anxiety. This may lead to anger and frustration when they focus on negatives instead of positives.

Psychologist Lewis Goldberg described these as the ‘Big 5’ factors of personality. A considerable amount of subsequent research in psychology has employed these five ‘super’ traits to identify correlations between behavior and personality.

Studies have found that individuals’ scores on the ‘Big 5’ factors are fluid, and can change with age. For instance, agreeableness levels tend to increase as we grow older (Donnelan et al, 2008).

These five factors can also vary depending upon a person’s gender. For instance, a study published in Frontiers in Psychology found higher levels of neuroticism in females than males (Weisberg et al, 2011).

Learn more about the five-factor model here

‘A’ and ‘B’ Personality Types

Can your personality affect your health? This question was the subject of decades of research conducted by two U.S. cardiologists, Ray Rosenman and Meyer Friedman. Since the 1950s, the pair conducted research into the relationship between personality, stress and health, culminating in a 1974 book entitled Type A Behavior and Your Heart.

Rosenman and Friedman had observed that some of the seats in their patient waiting room were significantly more worn than others. Moreover, the worn areas were in unexpected areas of the seats, such as at the front. They suggested that these seats were occupied by patients who fidgeted as their waited for their appointment. These anxious patients would also stand and sit more than normal, causing the additional wear on the seats.

The cardiologists proposed that this group of patients exhibited Type A personality traits. Type A personalities are more prone to experience stress: they are impatient, often anxious and are susceptible to stress when under pressure.

People in this category contrast with those with Type B traits. Such people are less affected by stressful situations and are able to ‘let go’ of worries that would preoccupy Type A personalities.

In a longitudinal study, Friedman and Rosenman found that participants who exhibited Type A behavior were more likely to suffer from coronary heart disease (CHD) than the rest of the sample  (Rosenman and Friedman, 1974).

Whilst these findings demonstrate a link between personality and susceptibility to stress, the reliability of the research has subject to criticism, partly due to the role played by the tobacco industry in funding the work. Friedman and Rosenman’s early research also focussed on a male sample, raising the question of whether its findings can be generalised.

Friedman and Rosenman also emphasize that the effects associated with the Type A personality may be associated with its typical ‘behavioral patterns’, rather than being directly determined by an individual’s personality. In a subsequent paper, they suggest ways in which those with a Type A personality may opt to alter their behavior and the way in which they respond to stress (Rosenman and Friedman, 1977).

  1. Eysenck, H. J. (1947). Dimensions of Personality. London: Routledge & Kegan Paul.
  2. Eysenck, H. J. and Eysenck, S. B. G. (1976). Eysenck personality questionnaire. Educational and industrial testing service.
  3. Donnellan, M. B. and Lucas, R. E. (2008). Age Differences in the Big Five Across the Life Span: Evidence from Two National Samples. Psychology and Aging. 23(3). 558-566.
  4. Weisberg, Y. J., DeYoung, C. G. and Hirsh, J. B. (2011). Gender differences in personality across the ten aspects of the Big Five. Frontiers in Psychology. Retrieved from
  5. Rosenman, R. H. and Friedman, M. (1974). Type A Behavior and Your Heart. New York: Random House.
  6. Rosenman, R. H. and Friedman, M. (1977). Modifying type A behavior pattern. Journal of Psychosomatic Research. 21(4). 323-331.
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