A team of researchers at Northwestern University has sifted through data from more than 1.5 million people around the world and found at least four distinct clusters of personality types exist: average, reserved, self-centered and role model. The results, published in the journal Nature Human Behaviour, challenge existing paradigms in psychology.

Understanding human personality has been a focus for philosophers and scientists for millennia.

It is now widely accepted that there are about five major personality domains that describe the personality profile of an individual. In contrast to personality traits, the existence of personality types remains extremely controversial.

“People have tried to classify personality types since Hippocrates’ time, but previous scientific literature has found that to be nonsense,” said Professor William Revelle, co-author of the study.

“Now, these data show there are higher densities of certain personality types.”

“Personality types only existed in self-help literature and did not have a place in scientific journals. Now, we think this will change because of this study,” added Professor Luís Amaral, senior author of the study.

The scientists developed an alternative approach to the identification of personality types and applied it to four large data sets comprising more than 1.5 million participants.

From those robust datasets, they plotted the five widely accepted basic personality traits: neuroticism, extraversion, openness, agreeableness and conscientiousness.

After developing new algorithms, four clusters emerged:

(i) average — average people are high in neuroticism and extraversion, while low in openness; females are more likely than males to fall into the average type;

(ii) reserved — this type is emotionally stable, but not open or neurotic; they are not particularly extraverted but are somewhat agreeable and conscientious;

(iii) role models — role models score low in neuroticism and high in all the other traits; the likelihood that someone is a role model increases dramatically with age; more women than men are likely to be role models;

(iv) self-centered — self-centered people score very high in extraversion and below average in openness, agreeableness and conscientiousness; there is a very dramatic decrease in the number of self-centered types as people age, both with women and men.

To be sure the new clusters of types were accurate, the team used a notoriously self-centered group — teenaged boys — to validate their information.

“We know teen boys behave in self-centered ways. If the data were correct and sifted for demographics, they would turn out to be the biggest cluster of people,” Professor Amaral said.

Indeed, young males are overrepresented in the self-centered group, while females over 15 years old are vastly underrepresented.

“Along with serving as a tool that can help mental health service providers assess for personality types with extreme traits, the study’s results could be helpful for hiring managers looking to insure a potential candidate is a good fit or for people who are dating and looking for an appropriate partner,” Professor Amaral noted.

“And good news for parents of teenagers everywhere: as people mature, their personality types often shift. For instance, older people tend to be less neurotic yet more conscientious and agreeable than those under 20 years old.”

“When we look at large groups of people, it’s clear there are trends, that some people may be changing some of these characteristics over time. This could be a subject of future research.”

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Martin Gerlach et al. A robust data-driven approach identifies four personality types across four large data sets. Nature Human Behaviour, published online September 17, 2018; doi: 10.1038/s41562-018-0419-z