For the study, researchers analyzed data from over 1.5 million questionnaire respondents. The results revealed that there are at least four specific clusters of personality types: average, reserved, self-centered, and role model.
These clusters are based on the five widely accepted basic personality traits, which are agreeableness, conscientiousness, extraversion, neuroticism, and openness. Each of the five personality factors represent a range between two extremes. For instance, extraversion indicates the continuum between extreme extraversion and extreme introversion.
The researchers noted that the results of the study challenge existing paradigms in psychology. (Related: People who don’t take themselves too seriously tend to have greater psychological well-being, according to study on humor.)
Luís Amaral, who is from Northwestern's McCormick School of Engineering, led the study. William Revelle, study co-author and professor of psychology in the Weinberg College of Arts and Sciences, said that while people have tried to determine personality types since Hippocrates' time, earlier scientific data has shown that these attempts are "nonsense."
Revelle, who is an expert in personality measurement, theory, and research, added that findings from the current study revealed that there are higher densities of specific personality types. At first, Revelle doubted the study's premise since the concept of personality types is controversial in psychology. Hard scientific proof is hard to find and earlier attempts based on small research groups often had results that weren't easy to replicate.
Amaral, the Erastus Otis Haven Professor of Chemical and Biological Engineering at Northwestern Engineering, explained that personality types only existed in self-help literature. Researchers like him didn't think it was worthy of documentation in scientific journals, but the study could very well change their minds.
In the study, researchers combined an alternative computational approach with data from four questionnaires. They worked with data gathered from "over more than 1.5 million respondents from around the world obtained from John Johnson's IPIP-NEO with 120 and 300 items, respectively, the myPersonality project and the BBC Big Personality Test datasets."
The research community developed the questionnaires for several decades, which included 44 and 300 questions. Volunteers who took the online quizzes took the chance to receive feedback based on their personality. These data are currently being made available to other researchers for independent analyses.
Amaral commented that the study is unique because it worked with a large dataset, which wouldn't have been possible without the internet. In earlier studies, researchers would have had to observe several hundred undergrad volunteers on campus. Thanks to current technological advances, researchers now have easy access to various online resources available and data is easier to share.
Using the datasets, the researchers plotted the five basic personality traits. The algorithms helped determine the four personality clusters.
Amaral shared that the research team's first attempt to sort the data using traditional clustering algorithms produced inaccurate results.
Revelle said that the team initially presented 16 personality types, which he said was absurd. He then instructed Amaral and Gerlach to refine the data.
Amaral noted that while machine learning and data science are promising, the results they produce still need to be verified. The team then developed a new method to guide people to solve the clustering problem so the findings can be tested.
When the data came back, Revelle said that they kept finding the same four clusters of higher density. Replicating the data confirmed that the results were "statistically unlikely." Revelle believes that the methodology is the paper's main contribution to science.
The researchers tested the accuracy of the test results on teenage boys, an age group that is "notoriously self-centered." Amaral confirmed that the teenage boys were overrepresented in the Self-centered group. Meanwhile females older than 15 are vastly underrepresented.
The study's results can be used to help mental health service providers assess for personality types with extreme traits. Amaral also said that hiring managers can reference the results to determine if a potential candidate is suited for a job.
Amaral concluded that there's a high chance that teenage boys won't always belong to the same personality type. As you age, you can grow out of certain characteristics and change over time.
The study was published in the journal Nature Human Behaviour.
Browse more articles about psychology and mental health at Mind.news.