The Evolution of Personality Theory: From Ancient Dispositions to Modern Trait Analysis

We each have a personality, with its unique characteristics. Some of us are extroverted, while some of us are more introverted. Some of us are creative and open-minded, while others are more pragmatic and practical. Some of us love a good argument or debate, while some of us would prefer to cooperate rather than compete, nurturing our relationships and social ties. We all embody a combination of different traits that make us the unique individuals that we are. But, where does our personality come from? Rather, what is our personality to begin with?

It all goes back to the ancient Greeks when Aristotle provided the first written account of personality traits, which he called ‘dispositions’. Back then, we didn’t have the vast scientific and psychological body of knowledge we do now, so Aristotle was limited to his own personal observations. He saw and described traits in others, like modesty, bravery, and vanity. Theophrastus, a student of Aristotle's, later expanded on his teacher's list and came up with 30 personality types that aimed to categorise individual differences. While these attempts to define personality were somewhat limited, given the lack of scientific knowledge at the time, they set the foundation for what was to come in the following centuries.

It wasn’t until the mid-19th century, with the development of statistical techniques like correlation and factor analysis, that we started to make some ground in identifying personality. This is when the personality types shifted into trait dimensions. A personality trait is a dimension used to categorise individuals based on how much they exhibit a characteristic. The use of personality traits comes from Trait theory.

There are two assumptions held in Trait theory: firstly, personality traits are relatively stable over time. The traits you possess right now, you’ve likely possessed them for an extended period of time, and you will likely continue to possess them for the long term. Our personalities tend to change quite rapidly through childhood, as our brains are highly plastic and our bodies undergo enormous shifts. However, if you’re around 25 years old and above, you might notice that any changes to your personality are more steady and subtle. This captures the essence of the first assumption of trait theory – that your personality is stable over time.

The second assumption is that traits show consistency across situations. So, let’s say you’re an extrovert. When you attend parties, you’re the life of the party. You’re charming, outspoken, gregarious, energetic, and you find yourself talking to many different people at these parties, not just the people you know. If you’re an extrovert at parties, it's likely that your trait extroversion will be consistent across other contexts, such as in the workplace. While both environments – work and party – are two distinct settings, your extroversion in one will likely show up in the other – hence the assumption that traits show consistency across situations.

So, how did Trait theory develop within psychology?

We can go as far back as the early 20th century, when American psychologist William Sheldon introduced a personality classification system called somatotypes. William Sheldon is considered to be the founding figure of trait psychology, and his classification system of personality traits was based on someone's physique and temperament. Sheldon identified three basic body types:

1. Endomorphy (soft and round): Sociable, fun-loving, relaxed, good-humoured.
2. Mesomorphy (muscular and athletic): Assertive, adventurous, bold, competitive.
3. Ectomorphy (slim and fragile): Introverted, thoughtful, sensitive, inhibited.

While these descriptions might sound outdated compared to what we know today, Sheldon’s work marked the beginning of using psychometric approaches to study personality.

During the same period, Gordon Allport, another American psychologist, was known for his influential work in trait psychology. With a colleague, he identified 18,000 words related to personality, of which 4,500 were considered personality traits. Gordon Allport went on to publish the first textbook on personality in 1921 and introduced the first personality course at a university in the United States in 1924.

Allport adopted a unified approach to personality, emphasising how a combination of traits produces unique individuals. He came up with three distinct categorisations for traits:

1. Cardinal Traits: Single traits that dominate personality, like competitiveness.
2. Central Traits: Five to ten traits that best describe an individual.
3. Secondary Traits: Traits that appear in specific situations but are not core to someone’s personality.

Shortly after Allport came a psychologist named Raymond Cattell, who sought to identify the basic structure of personality by reducing Allport’s extensive list of 4,500 traits into a smaller, more manageable set that could better represent the core components of personality. Cattell used a statistical technique called factor analysis to do this. Factor analysis involves identifying frequently used sets of words describing personality and then clustering them together to form single traits. For instance, the traits “determined”, “persistent”, “productive” and “goal-oriented” might correlate with “conscientiousness”, and so conscientiousness became the umbrella trait to describe all similar, correlated traits.

Raymond Cattell aimed to develop a comprehensive, empirically sound trait theory of personality. He believed that a good theory should predict behaviour, being one of the first to use complex mathematical formulas and statistical techniques to achieve this. His most notable contribution to psychology was the Sixteen Personality Factor questionnaire, which is used widely today in business and other fields. Contemporary sports psychologists find Cattell's 16PF effective in assessing elite mountaineers, identifying levels of tough-mindedness, achievement striving, and perseverance of athletes.

Hans Eysenck, a German-born British psychologist, came after Cattell. Eysenck took Cattell's 16 traits and concentrated them down to three main traits, called the three-factor model of personality. Eysenck’s approach to personality was grounded in biological and genetic factors, emphasising the role of heredity in shaping personality. His three-factor model, known as the PEN model, proposes that personality can be understood in terms of three major dimensions:

1. Extraversion: Sociability, assertiveness, liveliness, and a tendency to seek stimulation and the company of others. He suggested that extraversion has a basis in the brain, related to the level of cortical arousal. Extroverts have a lower baseline level of cortical arousal, leading them to seek external stimulation to raise these arousal levels.
2. Neuroticism: Emotional instability, anxiety, moodiness, and a tendency to experience negative emotion. Eysenck proposed that neuroticism is linked to reactivity of the autonomic nervous system, which is the system involved in the fight or flight response.
3. Psychoticism: Aggressiveness, impulsivity, aloofness, and a tendency toward antisocial behaviour. Eysenck believed psychoticism was associated with high levels of testosterone, triggering aggression and a lack of impulse control.

The study of personality has evolved significantly from the early observations of the ancient Greeks to the sophisticated statistical analyses of modern psychology. The development of trait theory by figures such as William Sheldon, Gordon Allport, Raymond Cattell, and Hans Eysenck has provided a robust framework for understanding the stable and consistent dimensions of human personality. These pioneers laid the groundwork for contemporary research, which continues to explore the intricate interplay of genetic, biological, and environmental factors in shaping who we are. As we continue to uncover the complexities of personality, the foundational work of these early psychologists remains integral to our understanding of human behaviour and individual differences.