The Evolution of Personality Research: A Brief Review of History

As humans, we are all intuitively aware that everyone is unique both psychologically and physically. One of the biggest obstacles in the scientific study of humans is how we can quantify these individual differences, and figure out a way to measure and account for them. In Psychology, in particular, you cannot discuss individual differences without touching upon the subject of Personality.

One of the most influential theories of modern Personality research was developed by Eysenck in 1947. While he was working at a psychiatric hospital in London, he compiled a battery of questions about behaviour to assess psychological disorders. What he realised was that answers to individual questions are often related to other questions, suggesting dimensions of personality traits are being revealed by that patient’s answers: initially Extraversion and Neuroticism as the 2 basic dimensions, and later on, Psychoticism.

However, Eysenck’s theory was criticised for having relatively weak methodology. Eysenck’s method of developing the basic dimensions of personality involved asking behavioural questions, then grouping answers to similar questions together. This method assumes that the original battery of questions was comprehensive, and also depends heavily on the way individual questions are worded and how answers are presented. For example, Eysenck used simple Yes/No answers, and it was argued that this was insufficient to represent the complexity of human personality (Helms, 1970).

Another approach was to use language, known as the Lexical Hypothesis (Galton, 1884). It starts with the assumption that personality characteristics most important to a society will eventually become a part of their language, and will gradually have evolved to be described by a single word. Using this hypothesis, Cattell (1943) grouped the single-word adjectives that describe mental states (in English) to construct 171 bipolar scales, which he then asked 100 college students to rate their peers on. The results were analysed using factor analysis.

However, this method yielded 16 primary personality factors, and 8 secondary factors. This was criticised by other researchers for being too complex, and another study attempting to replicate this result was unable to find evidence for anything more complicated than a 5-factor model. Later attempts to replicate the study concluded that out of the 24 personality factors proposed by Cattell, only 5 of them were consistently replicable, also known as the current Big Five Personality Traits. These traits have been labelled different things in different papers, but the interpretation is generally consistent: (I) Extraversion (also known as Surgency), (II) Agreeableness, (III) Conscientiousness (aka Dependability), (IV) Emotional Stability (or Neuroticism), and (V) Openness (also labelled as Culture or Intellect by other researchers).

One of the criticisms of the origins of the Big Five, the Lexical Hypothesis, was that it was heavily based on the English language, and therefore would be difficult to extrapolate results to other cultures who speak other languages. In fact, some psychologists believe that the language one speaks limits, or at the very least, influences one’s thoughts and cognitive processes. Some evidence for this theory (commonly known as the Sapir-Whorf hypothesis) stems from studies of languages that do not have number words more than 5 (for them, it goes: 1, 2, 3, 4, 5, many), or languages with only 2 colour words (black and white), with speakers of those languages finding it harder to recognise larger numbers or remember different colours respectively.

Over time, however, the Big Five have been applied in several different languages and cultures, including German, South Korean, Israeli and Filipino samples, among others, and support was found for the entire Five-Factor model, further grounding it as one of the most widely recognised personality models in Psychology.

Aside from being studied individually, the Big Five have also been applied in many areas of Psychology, from the study of psychological disorders, to the study of job performance, just to name a few. There has been an abundance of research regarding the Big Five and job performance, which is why here at Flexy, we’ve chosen to use the Big Five Personality Traits as our metric for analysing our workers. Flexy believes that even temporary workers should be motivated predominantly by job satisfaction, which comes from working in a job that is suited towards your personality. Because of the wide recognition of the Big Five, much of the literature regarding personality and job performance uses the Big Five, allowing us to base our algorithms on more solid scientific research.

Undoubtedly, individual differences among humans are very complex and therefore difficult to measure systematically. That is what makes the study of Psychology so interesting, the fact that no methodology is concrete and forged in stone. Our understanding of human psychology is constantly evolving, and our methods are constantly improving. All psychological discoveries were made via trial and error, to find the best method to measure and quantify the infinitely variable.

 

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