Personality Tests – Research Science Explained



Are you an INFP or an ESTJ? What about your Minnesota Multiphasic results, or how did you do on your Rorschach test? The Big Five? There are dozens of personality tests and assessments with varying degrees of utility. Which tests are backed by science, and which tests are more entertaining than helpful? Let’s find out.


A Brief History of Personality Tests

While personality assessments and tests have blown up in the past century, they originated for a simple purpose – help with personnel selection in the armed forces. More specifically, the developers of these tests hoped that by studying personality and potential mental health issues, one would be better able to determine which soldiers were better or worse suited to fly military aircraft.

Since then, dozens of personality assessments have emerged, each with a different theory on personality and how to best describe it. Our understanding of personality and models to describe and approximate it are purely human inventions, not concrete sciences. Each system has its own language and ideology, theories and philosophies in determining which traits are determinative and how to go about assessing them. How should we categorize traits? Are they binary or plotted along a bell curve?

While seemingly based in science, few have truly followed any resemblance of the scientific method. In fact, most assessments were built on the creators’ subjective feelings about personality, rather than rigorous scientific protocols. For that reason, most personality tests tell us less about the individuals who take them and more about the individuals who devised them.

For example, Hermann Rorschach was the Swiss psychiatrist who turned a parlor game into the iconic inkblot test. Starke Hathaway was a Midwestern psychologist who found it important to ask questions about religious beliefs, sex life, and bathroom habits in his Minnesota Multiphasic Personality Inventory, or MMPI for short. If you’ve gotten to your psych rotation in medical school, you’ve likely heard of the MMPI-2. And of course, there’s Isabel Myers and Katharine Briggs, the mother-daughter housewife duo who studied Carl Jung’s texts and were inspired to create a personality test despite having zero background, training, or credentials in anything psych related.


The Most Popular Personality Tests

Myers and Briggs are credited for creating the all too famous Myers Briggs Type Indicator, or MBTI for short. According to CPP, the publisher of the MBTI, it “measures four pairs of opposing preferences, which are inborn and value-neutral, to form a person’s four-letter type.” The assessment discerns between “Extraversion (E) or Introversion (I),” “Sensing (S) or Intuition (N),” “Thinking (T) or Feeling (F),” and Judging (J) or Perceiving (P),” resulting in 16 different personality types, like ENFP or ISTJ.

A few decades after the birth of the MBTI, in 1961 at Brooks Air Force Base, a group of scientists began developing what would become the Big 5 Personality Traits, or the 5-Factor Model. Rather than relying on their intuition to select criteria for their test, they compiled every word that could be considered a personality trait and created simple questions about them. For example, on a scale of 1 to 5, would you say you get upset easily? Do you follow a schedule? Based on these answers, the statisticians grouped traits that seemed to cluster together, such as talkative and sociable, into five basic categories: Extraversion, Conscientiousness, Agreeableness, Neuroticism, and Openness to experience.

Chances are that you’ve heard of Myers Briggs, but maybe you weren’t aware of the Big 5 or its more recent derivative, the HEXACO test. Why is that? Some suggest it’s because of the thousands of people who have invested time and money in becoming MBTI-certified trainers and coaches. Others say it’s because the test focuses only on the positive and therefore it seduces test takers with an image of their own ideal self. I argue that the biggest reason for its success is the neatly organized and binary manner of the test. There are four categories, each with a binary option. It’s easy to comprehend, easy to explain, and you’re able to readily identify with one of 16 tribes. As humans, we love our tribes. Other personality tests, on the other hand, are not binary and are more of a continuum, which is less entertaining, less easily understood, and less sexy.


What Does the Science Have to Say?

But unfortunately for the Myers Briggs Type Indicator, people and their personalities are not binary, but are much more on a continuum. You’re not a pure introvert or a pure extrovert, but usually somewhere in the middle. The insights of the MBTI are comparable to taro cards or palm reading – being generic enough such that when you read your description, you can certainly identify with parts of it, but it’s not a truly accurate and comprehensive depiction of who you are.


Scientific Validity & Reliability

When scientists look at such personality tests and assessments, two primary elements come to mind – validity and reliability.

Validity is a measure of how well a test measures what it claims to measure. Within validity, there are different types, such as content validity, criterion-related validity, construct validity, and face validity.

Reliability is a measure of whether the test reliably indicates accurate results, meaning you would get the same results if you took the test more than once.

Unfortunately for the MBTI, it receives piss poor scores on both fronts. In one study, researchers found that 50 percent of people received different results the second time they took the test, even just five weeks later. Other studies have found similar results ranging from 24-61% of people receiving different results when taking the test multiple times.


Additional Problems with the MBTI

The MBTI misses the mark in a few other ways, including one key element of personality – emotional stability versus reactivity, meaning the tendency to stay calm and collected under stress or pressure. This is one of the most important predictors of individual and group patterns of thought, feeling, and action.

The judging-perceiving scale reflects whether the test taker is more of a planner or the spontaneous type, but it overlooks the industriousness and achievement drive that accompany these characteristics. Together, they form a personality trait called conscientiousness.

Lastly, in the binary system of the MBTI, traits are mutually exclusive. For example, under this model, thinking and feeling are on opposite ends of a single spectrum, meaning that if you are drawn to ideas and data, you cannot also have a preference for people and emotions. But research has demonstrated the exact opposite, that people with stronger thinking and reasoning skills usually also demonstrate better emotional intelligence, being able to recognize, understand, and manage emotions.


Good News for The Big Five

While it’s a sad story for MBTI, there’s good news for the Big Five. The test was shaped by an empirical process and while not perfect, most studies since have demonstrated more acceptable levels of validity and reproducibility.

So far, studies have demonstrated considerable power in predicting job performance and team effectiveness. Some researchers have even mapped the big five to relevant brain regions. And while the Big Five model is far from perfect, there’s growing support for a HEXACO model of personality, which is essentially the Big Five with an addition of a sixth trait: honesty-humility.


So… Should I Use Personality Tests?

Despite the Big Five being far superior to Myers Briggs from a scientific validity and reproducibility standpoint, I don’t think it will catch on, at least for lay people. It’s just more catchy and easier to say you’re an INTP than saying you’re 56% on openness and 35% on neuroticism.

People sometimes expect personality tests to tell them some hidden secrets to their character. But the truth is that a personality test can only tell you what you tell it. Accuracy with the test is entirely based on how honest and self-reflective you are with your answers. If I told the test that I’m a super patient and one to readily forgive, it would sure make me feel good, but I would just be lying to myself.

But I’d argue there’s still utility to personality tests, even if they’re all far from perfect. And sure, entertainment should be one of the top reasons. Let’s be real, including your Myers Briggs on your online dating profile makes for a good conversation starter.

The real utility is in that it facilitates the process of introspection and reflection. Taking a personality assessment helps someone consider some of their strengths and weaknesses, and begin having difficult conversations. The most insightful realizations I’ve had in my own behavior, in my own ways of possible growth, wasn’t from seeing the results of a personality test, but from speaking with close friends and family about areas of improvement. A personality assessment isn’t a prerequisite, but it can help you get started.

For those who are newer to self-reflection, personality tests can help you consider possible blindspots. While Gretchen Rubin’s Four Tendencies is far from a perfect model, it helps one consider what external and internal factors motivate them to behave in certain ways. I even made a video applying her model to student life, helping you determine how to understand your personality tendency and use a variety of strategies and hacks to force yourself into being a better student based on that tendency. Is it a scientifically valid and reproducible model? The data is lacking, and I wouldn’t put my money on it, but hundreds of comments from students who successfully implemented and improved their performance is good enough for me.

Other critics are quick to state that your personality is fixed and resistance is futile. It’s a waste of effort. Why even try to change or improve yourself? Speaking from personal experience, I’d say you have far greater power over your own personality than you’d expect. It’s just that most people fail to make any significant changes because they don’t put in the proper effort in changing their systems. In fact, a recent meta-analysis demonstrated that approximately 40% of a person’s personality is due to genetic influence, while 60% can be attributed to environmental effects.


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