Why You Might Get Two Different Results On A Personality Test

Designed by Poppy Thorpe.
I’ve done my best to get into horoscopes, along with everybody else. But no matter how hard I try, I can’t make sense of myself as an Aquarius. Every horoscope, Instagram meme account and Aquarius explainer describes Aquarians (20th January to 18th February) as being "original", "independent", "guarded" and "averse to emotional expression". I, however, am known to cry just thinking about a dog in a hat, and will willingly share my life story with strangers, with or without alcohol.
My emotionality and openness is fundamental to me and, as such, means I just can't take my star sign seriously. Despite writing horoscopes off though, I am envious of how others use their star signs as explainers of their identity. As an anxious person I'd love to be able to package up my worrying into a neat box marked "classic Gemini".
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I decided I needed to find another, non-cosmic "label" for myself and so I turned to personality tests. For centuries, human beings have sorted each other into psychological types, from Hippocratic humourism to the racist science of 19th century phrenology. Systematic personality testing is a 20th century phenomenon and has become one of the most popular modes of self-discovery in recent times. Free online personality tests are the backbone of internet culture, from the quiz to reveal which Friends character you are to the Pottermore sorting hat, all the way through to the ones with actual scientific backing. The impulse to try and understand ourselves through categorisation has thrived online. It keys into our desire to feel simultaneously special and normal.
The most popular form of personality test is the Type Test, of which the Myers-Brigg Type Indicator (MBTI) is the most popular. These tests are "founded in Jungian typology" and break down personalities into discrete types. According to the MBTI, we all exist in four either/or binaries. You are either extroverted (E) or introverted (I), sensing (S) or intuitive (N), thinking (T) or feeling (F), judging (J) or perceiving (P). Our unique combination of these four factors adds up to create one of 16 personality types onto which some tests add the modifier of either turbulent (T) or assertive (A), resulting in 32 total variations. Although the official MBTI may cost upwards of £40, there are many free tests that directly pull from the MBTI model. The one I test myself with, which no doubt you have done too, is 16Personalities, one of the most popular and wide-reaching internet tests (with 214,248,607 tests taken at the time of writing). 
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I did the test twice in four days and I got two different results. Firstly, I was told I am a "Turbulent Advocate" (INFJ-T) which means I am a driven person who wants to "make a lasting positive impact" but gets stressed easily. So far, so relatable. Four days later I was recategorised as INFP-T, a "Mediator"; a type who are "true idealists, always looking for the hint of good, searching for ways to make things better". While my introversion rating stayed the same, my level of intuitiveness went down by 3%, my feeling by 2%, and I switched from being primarily judging to prospecting. And this isn't unique to me: there are studies that show that on the MBTI, as many as 50% of people receive a different result on their second go.
Both personality types felt 'true' to me, something which gives weight to the test's accuracy. Although I am mindful of a thing called the Forer Effect, named after an experiment which showed that people were more likely to believe that vague personality descriptions are uniquely about themselves without comprehending that they could also apply to others. It’s perhaps one reason why horoscopes and personality test results will so often feel spookily accurate. But what's with my two different results?
Jennifer Fayard, assistant professor of psychology at Ouachita Baptist University and author of the column "People Are Strange" at Psychology Today told me that our personalities do change over time, but not over the span of a few days. "Your personality should be stable from one day to the next, and if you're getting a different personality type, it's a sign that the test itself is not good."
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She continues: "The change you saw was most likely due to how the test is scored – if you were toward the middle of one of the dimensions to start with, answering some questions slightly differently the second time might have been enough to push you just to the other side of the middle, putting you in a different personality type altogether." She says that this is a  "problematic way of scoring tests because it makes it look like your personality has changed in important ways when it actually has not." A good personality inventory, she says, "will be resilient against temporary mood changes."
16Personalities does acknowledge the problem with binary archetypes, saying: "There is no single definition assigned to these type acronyms – each theory defines them in their own way and it is entirely possible that if you meet five people who all say 'I am an INFJ', their definitions of what INFJ means are going to differ." It is for this reason that they provide in-depth analysis and show, on a sliding scale, how much each letter applies to you. After all, there is a big difference between a 50% extrovert and a 99% extrovert.

But if you are on the cusp between one and the other (as I apparently am) that will not be reflected in your final lettered result. And it is in this result that the nuance of who we are can get lost when we interpret these types in ourselves, and in each other.

That’s not to dismiss how these tests can be used as a means of self-discovery – there is no wrong way to be in these frameworks, and they can guide you to potentially better understand yourself and people around you. But tests like these should be approached with a degree of caution – for better or worse, many may only be able to show you a sliver of who you are.
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