If there’s one thing individuals and Fortune 500 companies have in common, it’s the inability to resist a personality test. Employers have long used tests like the Myers-Briggs Type Indicator or the Enneagram to understand their employees better and build more compatible teams. And people in general seem strangely addicted to quizzes that categorize them by personality type.
It’s long been known that most personality tests aren’t scientifically sound, but that doesn’t stop people from taking them. Part of the reason is that those tests tell us something about ourselves as individuals while also making us feel like we’re part of a group identity. They seem to help us understand ourselves and one another better, and thus appear to “work.”
However, as researcher Madelyn Leembruggen explained on SciShow, most personality profiles simply play into a psychological trick we humans easily fall into.
The Barnum effect and how it works
“Personality tests and profiles take advantage of a weird psychological tendency that also benefits everything from horoscopes to fortune tellers to Buzzfeed quizzes,” Leembruggen said. It’s called the Barnum effect.
“The Barnum effect was named after P.T. Barnum, the iconic and problematic showman known for his ability to captivate, and often manipulate, an audience,” she explained. “The Barnum effect is the phenomenon where if you give someone a personality test, they’re pretty likely to believe that the results are true and accurate, regardless of how hard the profile-maker actually tried. There’s something about taking the test itself that makes an audience more likely to believe the end result.”
Personality tests became popular after WWI, when someone developed an assessment to determine which soldiers might be prone to PTSD. In the decades that followed, personality profiles appeared in popular magazines and psychologists’ offices alike. But researcher and college professor Bertram Forer felt skeptical about their accuracy. He basically said the results weren’t any more specific than saying that a person has opposable thumbs.

Professor Forer’s 1949 personality test experiment
In 1949, he conducted an experiment to test his hypothesis. He gave his Intro to Psychology students a personality questionnaire. Then, he told them he’d analyze the results and create a unique personality profile for each student. When they got their results, they rated them for accuracy. Only one student rated their results below a 4 out of 5, indicating nearly all students felt their results reflected their personality. However, Forer had duped them. He had actually given every student the exact same analysis.
“Forer made a list of general, vaguely flattering, and universally relatable statements,” Leembruggen explained. “So, why did everyone believe that their list was so perfectly tailored to them? Well, that’s the Barnum effect.”
Essentially, most personality descriptors in personality profiles are fairly relatable to most people. And when you combine any sense of the trait being positive, most people will see themselves in it.
The SciShow video gives these statements as examples:
“You have an analytical mind, though you also might space out at times.”
“You pride yourself as an independent thinker, and don’t accept other people’s statements without good proof.”
“You love variety and tend to rebel against too many restrictions and limitations.”
“You don’t always reveal all of yourself to others.”
“You have a great desire for other people to like and admire you.”
Most people see themselves in some, if not all, of those statements because they’re vague enough to feel true.
However, 1949 was a long time ago. Haven’t psychologists gotten better at creating real personality profiles?

How accurate is the Myers-Brigg Type Indicator, though?
One of the most popular personality tests of the past 50 years is the Myers-Briggs Type Indicator, or MBTI. This test splits people into 16 personality categories based on combinations of eight traits or preferences: Introversion/Extroversion, Sensing/Intuition, Thinking/Feeling, and Perceiving/Judging. Your “type” would be a combination of four letters, like INTP or ESFJ, with a corresponding description of that personality.
Many people have taken an MBTI test at work, but is it really accurate?
“When researchers want to see how well a certain assessment tool, test, or survey actually works, one thing they’ll do is have the same people take the same test multiple times,” Leembruggen said. “If they get the same score each time, we’d say that tool has good test-retest reliability. And in studies of MBTI where participants took the assessment multiple times, up to half or even more test takers received a different result for at least one of the four letters.”
Accurate or not, people love their Myers-Briggs. However, psychologists prefer a more recent personality indicator known as the Big Five Personality Trait model.
What is the Big Five Personality Trait model?
In the Big Five, people rank as low, medium, or high in five personality dimensions: extroversion, neuroticism, openness, conscientiousness, and agreeableness. (A more recent test known as HEXACO includes honesty-humility as a trait.)
“These tests, and newer variations that include subcategories of these five, do seem to show better test-retest reliability,” Leembruggen shared. “One major reason that newer tests based on the Big Five are more reliable is that they’re based on accumulating data from multiple long-term studies from the 1990s onwards. And they’re rooted in the principle that, if a personality trait exists in humans, languages will adopt words to describe it.”
However, she notes, most research only includes people from WEIRD countries: Western, Educated, Industrialized, Rich, and Democratic. That reality alone makes it hard to extrapolate universal personality traits or types.

The way personality tests are designed is inherently flawed
Finally, the nature of personality tests with multiple-choice answers, most of which only offer two options, is flawed.
“When you have to answer every question from a list of predetermined options, it’s called a forced-choice measure,” Leembruggen explained. “These tests are easy to administer and to grade, but the downside is that they’re really rigid and can flatten nuance, including how people’s personality traits can change due to the passage of time and other variables. We’ve all stared at a multiple-choice question and wished there was an option to check ‘other.’ So trying to make a questionnaire-style test that can accurately gauge anybody’s personality might be kind of impossible.”
That certainly won’t stop a lot of people from taking those tests, though. Accurate or not, there’s something about them that draws us in. Maybe it’s just fun to self-analyze. Maybe we yearn to know ourselves better, and those tests offer a structured and largely harmless way to do that—or at least to feel like we’re doing it.
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