These are the four major types of personality, according to science

Guidance counselors and self-help book writers value personality tests a lot, but not so much scientists. There is controversy between them as to whether well-defined personality types exist at all.

A big new study published in Human behavior nature, however, provides evidence for the existence of at least four personality types: average, reserved, egocentric and pattern. Each is based on the extent to which people present five different major character traits, including neurosis, extraversion, openness, amenity, and professional conscience.

"It seemed that personality traits were very well accepted and established in psychometrics, but personality types did not," said co-author of the study, Luis Amaral, professor of 39, chemical and biological engineering at Northwestern University. "I was just wondering if the reason people were not able to establish personality types was that there was not enough data?

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To answer this question, Amaral and his postdoctoral fellow Martin Gerlach reviewed 1.5 million responses to four different personality surveys conducted by people of all ages and ages. The pair used an algorithm to sort responses into different clusters and discovered four personality types that appeared in the four sets of survey data at a disproportionately high frequency.

According to Gerlach, most people will closely follow the average personality type, who is rather pleasant and conscientious, rather extrovert and neurotic, but not terribly open. Meanwhile, self-assessment-based types score below average for openness, agreeableness and professional conscientiousness, but they have high extraversion. Reserved individuals are relatively stable in all areas, with the exception of openness and neurosis, in which they are relatively weak. Finally, role models have high levels of extraversion, friendliness and awareness, and comparable levels of neurosis.

These groups continued to appear again and again. The Northwestern psychology professor, William Revelle, co-author of the article and long-standing doubter of personality types, was sufficiently intrigued by the results to change his mind. "There are higher densities than we would expect by chance, and that's what these guys have convinced me," Revelle says.

He compares the result to a map of the United States population. While people live across the country, it's easy to spot densely populated areas like New York, Los Angeles and Chicago, which are home to many more people than Cleveland or Tallahassee for example.

But, just as many people in the United States do not live in New York, Los Angeles or Chicago, some people do not fit in perfectly with one of the four personality types. Revelle says that they are just groups of traits that describe more people than average. Some people can adapt to it perfectly, while others are more vaguely associated with one of the camps. ("If you're in DC, you're closer to New York than to Chicago," says Revelle.) Some people may not fit in.

In fact, Gerlach says it's not possible to say exactly how many people fit into each category, because drawing rigid boundaries around them is both difficult and somewhat arbitrary. In addition, people's traits can change with age. A disproportionate number of young people, for example, fall into the category of self-centeredness, while more elderly people and women belong to the model group.

"People are growing," says Amaral. "People continue to be better integrated into society, acquiring more sociable traits over time."

Although researchers' findings add a dose of science to the study of personality, they say more research will be needed to turn the results into anything that could be useful to ordinary people, such as personality questionnaires or even dating services. Interested individuals can contribute to ongoing research by taking an online personality quiz, after which they will receive feedback from the researchers – which, according to Revelle, could be even more useful than knowing your personality type.

"It's helpful to know how far north or east is," he says. "More useful than saying in which city you live."

The research of the Northwestern team is not the only recent novelty in the field of personality. Last month, researchers at North Carolina State University developed a new personality test based on people's quick reactions to questions about the five major personality traits. They even developed a service, called PerSight Assessments, which they believe can be used by employers looking to find out more about new hires.