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Stuff You Should Know

Selects: How Personality Tests Work

Published November 15, 2025
View Show Notes

About This Episode

Josh and Chuck explore the history and mechanics of personality tests, focusing on the Myers-Briggs Type Indicator (MBTI), the Big Five traits, the Rorschach test, and the Minnesota Multiphasic Personality Inventory (MMPI). They discuss how these instruments were developed, how they are used in workplaces and legal settings, and the major scientific criticisms around their validity, reliability, and potential for misuse. The episode also touches on how people relate to labels, why these tests feel accurate, and ends with an email about anxiety, productivity guilt, and stepping away from television.

Topics Covered

Personality tests Myers-Briggs Type Indicator Rorschach test Psychometrics Introversion and extroversion Mental health Workplace dynamics Criminal psychology Personal Development Critical thinking

Disclaimer: We provide independent summaries of podcasts and are not affiliated with or endorsed in any way by any podcast or creator. All podcast names and content are the property of their respective owners. The views and opinions expressed within the podcasts belong solely to the original hosts and guests and do not reflect the views or positions of Summapod.

Quick Takeaways

  • Most popular personality tests, especially the Myers-Briggs, are not strongly supported by rigorous scientific evidence, yet they are widely used in corporate and legal contexts.
  • Attempts to classify personality go back to ancient ideas like the four humors and were later shaped by Carl Jung's typology and his introvert-extrovert concepts.
  • Modern psychometrics emphasizes traits like the Big Five and uses statistical methods and spectra rather than hard categories, unlike the dichotomous MBTI.
  • The MBTI was built by Catherine Cook Briggs and Isabel Briggs Myers from Jung's ideas by first deciding on types and then crafting questions to sort people into 16 categories.
  • Major criticisms of the MBTI include its lack of spectra, poor repeatability, entangled scales, and origins in untested theory rather than empirical research.
  • Projective tests like the Rorschach rely heavily on subjective interpretation and have been shown to mislabel healthy people as mentally ill, yet are still sometimes used in courts and custody cases.
  • The MMPI, while more empirically grounded and good at detecting faking, is extremely invasive and has been challenged when used in employment settings.
  • Positive, flattering test feedback taps into the Forer effect, explaining why people often feel that vague, generic descriptions "fit" them so well.
  • The hosts emphasize that personality is complex and fluid, and warn against letting any test result define your identity or determine high-stakes outcomes.

Podcast Notes

Select introduction and setup of the episode on personality tests

Josh introduces the Select episode and stakes of personality testing

Josh explains that this is a Select replay from August 2017 about personality tests[1:49]
• He notes that the vast majority of personality tests are scientifically faulty to some degree, and some are "outright made up"
Real-world consequences of faulty personality tests[1:49]
• Josh says this can be a serious problem if such tests are used to diagnose mental illness, hire or fire someone, or put someone in jail
• He emphasizes that these misuses actually happen in real life
Josh shares his own MBTI type[2:35]
• He casually mentions that he is an ENFP

Show intro and hosts' past experience with Myers-Briggs

Opening banter and mention of MBTI codes

Josh and Chuck open the Stuff You Should Know episode and reference MBTI letter strings[2:18]
• Josh calls himself and Chuck "a couple of ITJSs" jokingly, then admits he doesn't remember his actual type clearly
Company-administered Myers-Briggs session at HowStuffWorks[3:04]
• Chuck recalls that HowStuffWorks had Myers-Briggs administered years ago when they were owned by Discovery
• Josh notes it was paid for by Discovery, who brought someone into the office to administer the MBTI
• They joke that it was administered "at gunpoint"
Josh thinks he was ENFP in that test[3:10]
• Josh says looking at it again, he's pretty sure he was ENFP
• They riff jokingly that P stands for Pisces or "Pooper" before correcting it to "Perceiving" later

MBTI's ubiquity in corporate America

Prevalence of MBTI in companies[4:11]
• Josh explains that if you've been in corporate America for more than about three years, there's a good chance you've taken the MBTI
• Chuck cites stats: about 13% of U.S. companies use MBTI and 89 of the Fortune 100 use it
• They mention a 2001 stat that 10-40% of British companies used MBTI at that time, though they note the number is old and vague
MBTI as part of wider personality-test landscape[5:06]
• Josh notes there are tons of personality tests and MBTI is just one under that umbrella
• They say MBTI is probably the most famous personality test in pop culture, and this episode will cover MBTI, Rorschach, and other tests

Historical background: early attempts to classify personality

Ancient four humors and personality temperaments

Four bodily humors linked to disease and personality[6:32]
• Chuck recalls their past discussion of the four humors in an episode on grave robbing and early medicine
• They list the four humors: black bile, yellow bile, phlegm, and blood, originally used to explain disease
• Josh notes he didn't previously realize these humors were also linked to personality types
Temperaments: melancholic, phlegmatic, sanguine, choleric[7:36]
• Josh explains that "melancholy" in English comes from Greek for "black bile" and described a depressed, reserved personality
• They say people historically thought someone with a melancholic personality simply had an excess of black bile
• Chuck describes phlegmatic as very laid back and says Hippocrates refined these temperament concepts
• They list Hippocrates' four temperaments: melancholic, phlegmatic, sanguine, and choleric, with choleric being irritable and curt

Basic criticism: people don't neatly fit one type

Human personalities are too complex for single boxes[8:28]
• Josh points out that no one he knows is purely one temperament and that he himself cycles through all four humors sometimes in a single day or even a single happy hour
• He frames this as the central problem with personality classifications: trying to say "you're this one type" when personalities are too squishy and complex

Carl Jung's psychological types and influence

Jung's book and four psychological functions

Publication of "Psychological Types"[10:06]
• Chuck notes Jung wrote "Psychological Types" in 1921 in German and it was translated into English a couple of years later
Jung's four categories: sensation, intuition, thinking, feeling[11:08]
• They list Jung's categories and say most modern tests derive from these in one way or another

Jung introduces introversion and extroversion

Contribution of introvert-extrovert concept[12:02]
• Josh says beyond any criticisms of Jung, his introversion/extroversion concept is widely accepted inside and outside psychology
• He remarks that this one contribution alone would be enough to be carved on a tombstone
Introversion/extroversion as main orientation, with other functions modifying it[12:11]
• They explain that in Jung's system, each of the four functions is modified by whether you are introverted or extroverted
• Chuck notes Jung based these ideas on his own thinking and observations rather than heavy empirical research

Jung vs. empirical psychology and the birth of psychometrics

Psychoanalysis vs. quantitative approaches[13:18]
• Josh situates Jung as part of the early psychoanalytic movement alongside Freud, but notes that many psychologists now speak critically of Jung
• He explains that as psychoanalysis grew, a parallel movement arose that wanted quantifiable, numerical psychology
Early quantitative personality work[14:21]
• Josh mentions Alfred Binet, Gray and Wheelwright, and others who wanted to typify personality and add numbers to psychology to prove it as a science
• He says this desire to categorize people numerically spawned much of the modern personality-typing movement

Development and spread of the Myers-Briggs Type Indicator

Catherine Cook Briggs and Isabel Briggs Myers

Motivation to create MBTI during WWII[14:51]
• Chuck explains that Catherine Cook Briggs and her daughter Isabel Briggs Myers developed MBTI post-World War II as women entered the workforce in large numbers
• Their aim was to find what kinds of jobs women might be suited for or enjoy, by categorizing personality types
Briggs discovers Jung and restarts her work[15:40]
• Chuck says legend has it that Briggs had already been working on a personality test when she read Jung and dramatically threw her old work in the fire to start over
• Josh notes she was a voracious reader of European psychology and that Isabel later really ran with the work due to WWII labor needs

Stripping Jung's ideas and building MBTI

Which parts of Jung they kept and which they dropped[16:41]
• Chuck says they kept some of Jung's ideas but stripped away much of the unconscious material, which may have seemed too strange for the American workplace
• They ended up with the Myers-Briggs Type Indicator (MBTI) as a way to categorize people into types for work purposes

Publication, CPP, and MBTI's corporate marriage

Publishing history and CPP's role[17:05]
• Chuck says MBTI first had a publisher where it "didn't do very well," then switched in 1975 to Consulting Psychologists Press (CPP), its current publisher
• From the 1970s onward, MBTI's ubiquity in corporate America took off

Types of psychological tests and psychometrics basics

Projective vs objective tests

Projective tests: Rorschach as example[20:53]
• Chuck defines projective tests as those where you are shown a stimulus open to interpretation (like a Rorschach inkblot) and asked what you see
• A professional then quietly observes and takes notes to make an evaluation based on these projections
Objective tests: standardized questionnaires[21:09]
• Chuck explains objective tests as standardized assessments (like many personality inventories) scored and evaluated by professionals
• Josh points out that calling them "objective" is a misnomer because interpretation by a person reintroduces subjectivity

Psychometrics and the Big Five personality traits

Definition of psychometrics[21:45]
• Josh says the quantitative study of personality traits in psychology is called psychometrics
Overview of the Big Five traits[21:58]
• Chuck lists the Big Five: extroversion, agreeableness, openness to experience, conscientiousness, and neuroticism
• Josh elaborates that agreeableness involves being sympathetic, kind, and affectionate
• He defines conscientiousness as being organized, thorough, and punctual
• He says neuroticism (sometimes called emotional stability) involves being tense, moody, and anxious, and jokes that a bell goes off in his head when he hears the word
• He describes openness as having wide interests, being imaginative, and insightful
Traits as just one dimension of personality[23:57]
• Josh emphasizes that, according to one source he read, the Big Five traits are just one dimension among many parts of personality
• He lists other aspects like motivations, emotions, attitudes, abilities, self-concepts, social roles, autobiographical memories, and life stories as also important
• He says psychologists don't claim the Big Five are the whole personality; they give only a sketch that should be complemented by deeper study

Validity, reliability, and design issues in personality testing

Validity and reliability as key scientific standards

What validity and reliability mean[27:27]
• Chuck says a test's validity is whether it reflects the person accurately, and reliability is whether it produces the same result when retaken or using similar tests
• Josh notes reproducibility is essential if personality testing is to be considered real science rather than "hippy dippy questions"

Faking detection in tests like the MMPI

MMPI's mechanisms for catching fakers[28:54]
• Josh previews that the Minnesota Multiphasic Personality Inventory (MMPI) includes built-in mechanisms to detect people faking mental illness or hiding it
• He says MMPI is exhaustive and uses statistical analysis, so extreme patterns in either direction expose attempts to game the test
• Chuck notes one tactic is telling test-takers in advance that faking will be detected, which itself influences people to answer more honestly

How the MBTI works: structure, questions, and certification

The four MBTI dichotomies and 16 types

MBTI's goal: sort into one of 16 types[29:54]
• Chuck says MBTI's objective is to sort you into one of 16 personality types based on four paired dichotomies
First dichotomy: introversion vs extroversion (I/E)[30:08]
• They identify introversion vs extroversion as the most basic axis, using I or E in the four-letter code
Second dichotomy: sensing vs intuition (S/N)[30:30]
• Chuck clarifies that "sensing" means preferring empirical data and detailed information, while "intuition" means relying more on gut feelings
Third dichotomy: thinking vs feeling (T/F)[30:52]
• Thinking types focus more on logic and objectivity, while feeling types emphasize relationships and group harmony
Fourth dichotomy: judging vs perceiving (J/P)[31:14]
• Judging types prefer schedules and decisiveness, whereas perceiving types are more flexible and "whatever" about rigid structure
• Josh compares judging vs perceiving loosely to the famous (but unrelated) type A vs type B personalities, which he notes were created by cardiologists and later secretly funded by the tobacco industry

Example questions and word pairs

Trip-planning question[32:16]
• Chuck gives a sample MBTI-style question: when you go on a trip, do you want everything planned in advance or prefer to take each day as it comes?
Word-pair preference questions[32:41]
• He says they also use word pairs like "compassion" vs "foresight" or "carrots" vs "fruit" and ask which word you prefer

Cost of taking and administering MBTI

Individual costs and add-ons[33:47]
• Chuck says taking MBTI as an individual costs about $50, an hour of feedback costs about $100 more, and a career report costs extra
Certification to administer MBTI[34:31]
• Josh clarifies that the $1,500-$1,600 on-site training is a four-day course to become certified to administer MBTI
• He notes you cannot legally administer MBTI or you'll infringe on CPP's copyrights unless you are certified
• Certified practitioners then sell MBTI services to businesses, effectively becoming both evangelists and salespeople

MBTI's own framing: "indicator," not "test" and the handedness metaphor

MBTI says the test-taker is the expert[35:45]
• Chuck notes CPP emphasizes that the person taking MBTI is the expert on themselves
Handedness analogy for preferences[35:48]
• He explains MBTI uses the metaphor of writing with your dominant vs non-dominant hand to say types are about preferences, not absolute abilities
• Josh says the analogy doesn't fully land for him because he can barely sign with his off hand, whereas MBTI claims you can operate in your non-preferred modes

Major criticisms of the MBTI and misuse in corporations

Corporate use for hiring, firing, and promotion

MBTI explicitly warns against high-stakes use[40:04]
• Chuck says one big criticism is that companies use MBTI for hiring, firing, and promoting, even though CPP itself says not to do that
• Josh argues the real fault lies with corporations that treat the results that seriously, and says an HR person who hires/fires based on MBTI should themselves be fired

Intended use: team-building and appreciating differences

MBTI sessions as fun team-building days[41:10]
• Chuck recalls their office MBTI day was fun, with joking and candy, and no one taking it too seriously
• Josh says MBTI is often pitched as a team-building tool where people learn they're different and are encouraged to respect each other's perspectives
All types are framed as positive[42:02]
• Josh notes MBTI has no negative types and presents all 16 as equal and positive, giving everyone a kind of "participant ribbon" in the form of a type

Scientific criticisms: shaky foundations and lack of spectra

Based on Jung's untested theories[43:33]
• Josh says MBTI is grounded in Jung, whose ideas were based on personal observations rather than rigorous science and whose work many psychologists have disavowed
Dichotomies instead of continua[43:05]
• They highlight that MBTI forces you into one side of a dichotomy rather than placing you on a spectrum, unlike many psychometric tests that produce bell-curve distributions
Non-repeatability and the "cusp" explanation[43:41]
• Chuck notes critics say MBTI isn't very repeatable; people can get ENFP one day and a different type another day
• He says MBTI defenders claim that if results change, you were on the cusp near the centerline, but there is no formal category for "down the center"
Arbitrary cutoffs: height analogy[45:29]
• They cite a criticism that if MBTI measured height, it would classify people only as tall or short with arbitrary cutoffs, ignoring those in the middle
• Josh adds that two people with very different answer patterns can end up with the same letter (e.g., 24/24 vs 13/11 split) which flattens nuance

Construction problems and entangled scales

Self-report bias[46:15]
• Josh underscores that MBTI relies on self-reporting, which inherently introduces bias that's nearly impossible to eliminate
Overlap between dichotomies[46:25]
• They mention that answers on the judging-perceiving scale correlate with those on the sensing-intuition scale, meaning these supposed independent dimensions are entangled
• Josh points out MBTI was developed backwards: they chose the types first, then built a test to find those types, rather than discovering types empirically from data

Rorschach test: history, defenses, and serious problems

Origins and Exner's comprehensive system

Hermann Rorschach's inkblots[49:36]
• Josh says the Rorschach test, created by Swiss psychiatrist Hermann Rorschach around the 1910s, is the epitome of subjective self-reporting
John Exner's attempt to quantify Rorschach[50:11]
• They describe how John Exner created the "Comprehensive System" with about 140 components to systematically score Rorschach responses
• Josh notes Exner's work likely kept Rorschach from disappearing and that there is even an institute in Asheville dedicated to it

Cult-like adherence and cross-criticisms among test camps

Tribalism around different personality instruments[51:03]
• Josh observes that each testing instrument has dedicated adherents and detractors, resembling cults clustered around different figureheads like Rorschach or MBTI's creators

Evidence of inaccuracy and harm

Study mislabeling schoolchildren as psychotic[51:26]
• Josh cites a 2000 study where Rorschach was given to about 100 mentally sound elementary school kids and many were labeled borderline psychotic
Chuck's online Rorschach experience[52:18]
• Chuck says he took an online Rorschach-style test and scored two out of ten, with the result indicating he was only two points away from being labeled psychotic
• He describes seeing multiple different images (bats, bunnies, Mardi Gras masks) in the same blot, highlighting ambiguity
Use in courts and custody cases[53:17]
• Josh stresses the serious problem that Rorschach results are still used as evidence in criminal trials, child custody, and civil cases
• He argues it's unacceptable that lives are changed based on century-old inkblots and subjective interpretation

Minnesota Multiphasic Personality Inventory (MMPI) strengths and flaws

Design and empirical basis of MMPI

Development at University of Minnesota[54:52]
• Josh says MMPI was created in the 1940s at the University of Minnesota by a psychiatrist and a neurologist
Use of a control group for scoring[55:31]
• He explains they gave hundreds of true/false items to patients' family and staff at a mental hospital, assuming this group was sane, and used their answers as the baseline
• Subsequent test-takers' answers are compared to this control group to infer mental illness

Criticisms: questionable baseline and invasiveness

Questioning the "sane" control group[55:43]
• Chuck argues it's problematic to treat a group of mid-20th-century Minnesotans as the global standard of sanity
Tool of mid-century conformity[57:30]
• Josh cites sociologist William White, who said MMPI helped create and perpetuate mid-century "organization man" conformity, defining normalcy as a narrow profile and excluding others
Detection of faking and legal challenges in employment[56:12]
• They say MMPI is widely regarded as good at detecting people faking mental illness or trying to hide issues
• Josh notes the test is very invasive and that lawsuits have been brought against companies using MMPI for hiring and firing

Personality tests vs astrology and the Forer effect

Comparisons to astrology and positive framing

Why tests feel accurate: all positive, like horoscopes[58:16]
• Chuck says skeptics liken MBTI to astrology because feedback is framed positively and no one walks away feeling bad, similar to how horoscopes rarely deliver harsh messages

Bertram Forer's experiment and the Forer effect

Forer's demonstration using identical feedback[59:55]
• Josh recounts how psychologist Bertram Forer gave students a personality test, then handed each student the exact same feedback supposedly tailored to them
• The feedback was composed from horoscope statements and was generally flattering, telling people they had unused potential and positive traits
• About 85% of the class rated the generic description as highly accurate for them, illustrating the Forer effect
• They note that the more flattering the description, the more likely people were to see it as accurate, explaining MBTI's appeal despite weak scientific backing

Listener mail: anxiety, productivity guilt, and stepping away from TV

Mac's email about anxiety and relaxation

Abandoning guilt about productivity[1:01:19]
• Josh reads an email from Mac in the UK, who says he struggled with anxiety and difficulty relaxing
• Mac describes reading an article claiming our obsession with productivity and the guilt around not being productive are modern phenomena, which helped something "click" for him
• He decided to abandon guilt and embrace relaxation, taking control of his stress levels
Role of the podcast and walking in his new routine[1:01:42]
• Mac says listening to the podcast while slowly pottering around his flat and going for walks has lifted his mood and improved his mental health
• He says although some topics aren't positive, the hosts' explanations and views revive his hope in humanity

Television, anxiety, and idea for a future episode

Quitting TV and noticing its effects[1:02:16]
• Mac mentions he abandoned watching television, noting it hadn't helped his anxiety, especially after his partner subscribed to an online provider
Suggestion to explore TV's psychological impact[1:02:35]
• He references reading that after TVs became mainstream in Bhutan, the crime rate went up dramatically, and suggests this could be an interesting topic for a future show

Hosts' response

Gratitude and note on anxiety relief[1:02:44]
• Josh and Chuck express appreciation, say many listeners report the show helps with anxiety, and acknowledge they don't really know why but are glad it helps

Lessons Learned

Actionable insights and wisdom you can apply to your business, career, and personal life.

1

Personality is too complex and fluid to be fully captured by a single label or four-letter code, so any test result should be treated as a loose description of tendencies rather than a fixed identity.

Reflection Questions:

  • • In what situations do you most feel boxed in by labels others have given you, and how might you consciously push beyond them?
  • • How could viewing your personality as a spectrum of tendencies instead of a fixed type change the way you approach your strengths and weaknesses?
  • • What is one label you currently apply to yourself that you could reinterpret as "sometimes true" instead of "always true" this week?
2

Before trusting a psychological instrument, you need to ask whether it is valid, reliable, and being used appropriately for the decision at hand.

Reflection Questions:

  • • What tools or assessments are currently influencing big decisions in your life or organization, and have you ever questioned their scientific grounding?
  • • How might your approach to hiring, promotion, or self-development change if you required clear evidence of validity and reliability for any test you use?
  • • What is one assessment or metric you rely on that you could investigate more deeply this month to understand its strengths and limitations?
3

Flattering, generalized feedback feels accurate because of the Forer effect, so you need to maintain critical distance when a description "sounds just like you."

Reflection Questions:

  • • When was the last time you read a personality description or horoscope and thought "that's me," and did you consider how many others it could also apply to?
  • • How would you evaluate the next personality report you receive if you deliberately looked for what is vague, universally appealing, or non-falsifiable?
  • • What specific criteria could you adopt to distinguish genuinely useful feedback about yourself from feel-good, generic statements?
4

Using psychological tests in high-stakes contexts like hiring, firing, custody, or criminal trials can cause real harm when the tools are poorly supported or misapplied.

Reflection Questions:

  • • Where in your work or community have you seen people rely on simplistic metrics or labels to make serious decisions about others?
  • • How could you advocate for more cautious, evidence-based use of assessments in your organization or profession?
  • • What is one concrete step you could take this quarter to ensure that decisions affecting people's livelihoods or rights are based on multiple, well-founded sources of information rather than a single test?
5

Letting go of constant productivity guilt and building intentional relaxation into your life can significantly reduce anxiety and improve well-being.

Reflection Questions:

  • • Where do you notice a sense of guilt when you're not "doing something productive," and how is that affecting your stress levels?
  • • How might your mental health change if you deliberately scheduled unstructured, judgment-free time for walking, reading, or listening to something enjoyable?
  • • What is one small, relaxing practice you could experiment with this week to replace a habit (like passive screen time) that tends to increase your anxiety?

Episode Summary - Notes by Casey

Selects: How Personality Tests Work
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