Between a third and half of people who retake the MBTI just weeks later get a different personality type, revealing it as unreliable and closer to a coin flip than a valid test.
Where this was said
At 58:43 · chapter starts 46:00
Mark traces the MBTI's unlikely origin story: Katherine Briggs obsessively translated Carl Jung's work for American audiences, then her daughter Isabel — a novelist without a psychology degree — saw an opportunity when women flooded the WWII workforce and needed rapid job-fit assessment. She built a test from her dining room table, combining Jung's two 'attitudes' and four 'functions' with a fourth spectrum she essentially invented (perceiving vs. judging). Zero peer review, zero control group. The test spread virally through government agencies, then corporate consultants, until by the 1980s 89 of the top 100 global companies administered it. Today 2 million people per year take it in corporate settings. Drew then lists the scientific indictments: 33–50% get different results weeks later; it uses binary categories on what are actually spectra; it doesn't measure neuroticism; and unlike the Big Five, it cannot reliably predict job performance, relationship satisfaction, or mental health outcomes.
An estimated 2 million people per year take the MBTI in a corporate setting, despite it lacking scientific validation and failing to reliably predict job performance or relationship outcomes.
A third to half of MBTI takers get a different result just weeks later. It has no measure of neuroticism — arguably the most predictive trait for mental health. It cannot reliably predict job performance, relationship satisfaction, or any major life outcome. The Big Five does all of this consistently. The MBTI survives purely because it flatters and labels us, not because it works.
The widely cited ego-depletion model — the idea that willpower is a finite resource that gets depleted — failed to replicate in follow-up studies.
Humans are estimated to have 5,000–7,000 thoughts per day, yet can recall essentially none of them afterward, highlighting why in-the-moment emotional tracking matters.
A large Harvard study found that a wandering mind is an unhappy mind — people report greater happiness when their attention is tethered to the present, even if the task is unpleasant.
A key study finding that we have a 'credit card's worth of plastic' in our bodies was likely skewed because researchers used nitrile gloves that shed plastic particles onto the microplastic detector.
Emotionally sensitive people have a hyperactive amygdala, an underactive prefrontal cortex, and a frayed connection between the two — making emotional regulation structurally harder.
Rejection sensitivity can be observed as early as age 2 or 3, suggesting it has strong developmental and likely genetic roots.
A Yale study found that non-judgmental observation of emotions — without rushing to resolve them — reduces activation in the brain, making it a powerful regulation tool.
Dan Gilbert's research found that the psychological immune system — the brain's ability to justify and find satisfaction in choices — activates most powerfully when a decision is perceived as irreversible.
Barry Schwartz's research found that maximizers — people who try to optimize every decision — tend to achieve objectively better outcomes but report lower happiness than satisficers who choose 'good enough.'
We use essential and analytics cookies to run Vuci. To understand how the site is used: Privacy Policy.
Install Vuci on your phone
Add it to your home screen for a faster, app-like experience.
Install Vuci on your phone
Tap the Share button, then “Add to Home Screen”.
A new version is available
Reload to get the latest Vuci.