Since Hippocrates first suggested personality types might exist in the 4th century BC there have been attempts to group people by their character traits.
But despite the claims of self-help gurus and pseudo-psychologists, scientists have largely dismissed the idea that humans can be pigeon-holed into a handful of defined dispositions, until now.
Researchers at Northwestern University in Illinois sifted through data from more than 1.5 million questionnaire respondents and found at least four distinct clusters of personality types: average, reserved, self-centered and role model.
And good news for parents of teenagers. As people mature, their personality types shift with older people growing more conscientious and agreeable than those under 20 years old.
The researchers claim the findings are so important they challenge existing wisdom in psychology.
“Personality types only existed in self-help literature and did not have a place in scientific journals,” said study author Luis Amaral, the Erastus Otis Haven Professor of Chemical and Biological Engineering at Northwestern Engineering.
“Now, we think this will change because of this study.”
The concept of personality types is controversial in psychology, with hard scientific proof difficult to find.
Previous attempts to define character groups were largely based on small research groups, which could not be replicated.
But the researchers decided to take advantage of a new phenomena of people taking online quizzes to try and learn more about their own personality.
The new study used answers from four online questionnaires including the BBC Big Personality Test.
“The thing that is really, really cool is that a study with a dataset this large would not have been possible before the web,” added Dr Amaral.
“Previously, maybe researchers would recruit undergraduates on campus, and maybe get a few hundred people. Now, we have all these online resources available, and now data is being shared.”
From those datasets, the team plotted the five widely accepted basic personality traits: neuroticism, extraversion, openness, agreeableness and conscientiousness.
After developing new algorithms, four clusters emerged. Average people, who are high in neuroticism and extraversion, while low in openness, Reserved people who are emotionally stable, but not open or neurotic, as well as Role Models and Self-Centered individuals.
“The data came back, and they kept coming up with the same four clusters of higher density and at higher densities than you’d expect by chance, and you can show by replication that this is statistically unlikely,” said co-author William Revelle, professor of psychology in the Weinberg College of Arts and Sciences.
“I like data, and I believe these results. People have tried to classify personality types since Hippocrates’ time, but previous scientific literature has found that to be nonsense.
“Now, these data show there are higher densities of certain personality types,” said Revelle, who specializes in personality measurement, theory and research.”
To be sure the new clusters of types were accurate, the researchers used a notoriously self-centered group - teenaged boys - to validate their findings
“We know teen boys behave in self-centered ways,” added Dr Amaral. “If the data were correct and sifted for demographics, they would they turn out to be the biggest cluster of people.”
Young males were found to be overrepresented in the Self-Centered group, while females over 15 years old are vastly underrepresented.
The research was published in the journal Nature Human Behaviour.