Selects: How Personality Tests Work

Summary of Selects: How Personality Tests Work

by iHeartPodcasts

57m•November 15, 2025
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Overview of Selects: How Personality Tests Work

This episode (Stuff You Should Know — "Selects: How Personality Tests Work") reviews the history, methods, popularity, and scientific problems of personality testing. Hosts trace tests from ancient humors through Jung and the Myers‑Briggs Type Indicator (MBTI), compare major modern approaches (projective vs objective; MBTI vs the Big Five), and highlight real-world consequences when flawed tests are used for hiring, court cases, or diagnoses.

Key topics covered

  • Brief history: ancient four humors → Carl Jung’s Psychological Types (1921) → Myers & Briggs (MBTI) in WWII era.
  • Two broad test families:
    • Projective tests (e.g., Rorschach inkblots) — open interpretation of stimuli.
    • Objective tests (standardized questionnaires, e.g., MBTI, MMPI, Big Five assessments).
  • The MBTI: 4 dichotomies (E/I, Sensing/Intuition, Thinking/Feeling, Judging/Perceiving) → 16 labeled "types"; its corporate ubiquity and commercialization.
  • The Big Five (OCEAN): Openness, Conscientiousness, Extraversion, Agreeableness, Neuroticism — treated as dimensions/spectra and more accepted in academic psychology.
  • Psychometrics fundamentals: validity (does it measure what it claims?) and reliability (are results reproducible?).
  • Tests used in high-stakes situations: hiring, firing, child custody, criminal trials — and associated ethical/legal risks.

Main takeaways / conclusions

  • Many popular personality tests (especially MBTI and some projective tools) have weak scientific grounding. They often arose from observation and theory rather than rigorous, peer‑verified empirical research.
  • Dichotomous labeling (you're X or Y) is misleading: personality traits are better modeled on continua. Tests that force binary categories obscure nuance and can be unstable over time.
  • Self‑report tests are vulnerable to bias and intentional gaming; well‑constructed psychometric instruments try to counter this (e.g., multiple question formats, validity scales) but not all tests do so well.
  • Projective tests like the Rorschach can be highly subjective and have produced false positives (labeling healthy people as mentally ill). Standardization efforts (e.g., Exner’s Comprehensive System) reduced but did not eliminate problems.
  • MMPI (and later MMPI‑2) is exhaustive and has been useful for detecting faking, but origins and baseline (control group) choices invite critique; it's also invasive and problematic if misapplied by employers.
  • Despite scientific criticism, MBTI is widely used in corporate/team-building contexts. Creators/publishers often discourage using MBTI for hiring decisions, but misuse still occurs.
  • The Forer/Barnum effect: people accept vague, flattering statements as uniquely accurate (explains why horoscopes and some personality feedback feel convincing).

Notable details & examples mentioned

  • MBTI origins: inspired by Jung’s typology; developed by Catherine Cook Briggs and Isabel Briggs Myers during/after WWII to help match people (esp. women entering workforce) to roles.
  • MBTI mechanics: 4 letter code (e.g., ENFP). Certification to administer MBTI is available through CPP; administering without certification infringes copyrights.
  • MBTI pricing examples (as cited in the episode): test ~ $50; hour of feedback ≈ $100; full career report ≈ $1,695; certification course ~$1,500.
  • Big Five is widely accepted among psychologists because it models traits as dimensions rather than forced types.
  • Rorschach history: Hermann Rorschach (early 20th century); Exner (1970s) developed a quantitative “Comprehensive System” to standardize scoring.
  • MMPI: developed at University of Minnesota in 1940s; later revisions created the MMPI‑2 (long instrument, several hundred items); designed with a normative control group from hospital staff/families initially — a basis for criticism.
  • Type A/B personality research was influenced by funding that had industry bias (example cited: tobacco industry interest in type A explanations).

Criticisms & limitations (summary)

  • Lack of scientific basis: many popular tests were not developed by following modern experimental methods (e.g., MBTI created types first, then made questions to fit).
  • Dichotomy vs. spectrum: forced binaries (MBTI) ignore continuous distributions and introduce artificial splits.
  • Self‑report bias and faking: answers can be distorted intentionally or by social desirability.
  • Poor reliability: people may get different MBTI "types" over time or across different instruments.
  • Misuse in high‑stakes decisions: hiring, firing, legal judgments, child custody — can harm people when non-validated tools are given undue weight.
  • Projective tests: high subjectivity, risk of false positives for mental illness; problematic as evidentiary tools.
  • Cultural and sampling biases in normative baselines (e.g., early MMPI control groups).

Practical recommendations (for listeners, employers, and clinicians)

  • Treat any personality test as a conversation starter or descriptive snapshot — not an immutable label or sole basis for major decisions.
  • Prefer validated, dimension‑based assessments (e.g., Big Five instruments) when you need scientifically defensible trait measures.
  • For hiring or promotion: use tested job‑performance criteria, structured interviews, validated competency assessments — avoid relying solely on MBTI/MMPI/Rorschach results.
  • If you’re asked to take a personality test for employment, ask how results will be used, who will see them, and whether a licensed professional interprets them.
  • If using tests for therapy or diagnosis, consult trained clinicians who can integrate test data with clinical interviews and broader observation.
  • Be cautious about online/cheap versions of classic tests — many are oversimplified and not equivalent to validated instruments.

Useful concepts & terms explained

  • Projective test: Presents ambiguous stimuli; relies on subject’s interpretations (e.g., Rorschach).
  • Objective test: Standardized questionnaires with structured scoring (e.g., MBTI, MMPI, Big Five inventories).
  • Validity: Does the test measure what it claims to measure?
  • Reliability: Does the test give consistent results over time and across forms?
  • Forer (Barnum) effect: People find vague, flattering personality statements personally meaningful.

Where to learn more (suggested searches)

  • Myers‑Briggs Type Indicator (MBTI) history and publisher CPP (consult critiques and official guidance).
  • Big Five / OCEAN personality model (academic literature and validated Big Five inventories).
  • Rorschach controversies and Exner’s Comprehensive System (critique vs supporters).
  • MMPI and MMPI‑2 (origins, revisions, legal/ethical use).
  • Forer/Barnum effect (classic psychology demonstration).

Quote highlights from the episode (paraphrased)

  • “Personality tests try to put something squishy — the human personality — into a box, and that’s where a lot of the problems start.”
  • “Treat results as preferences or tendencies — not as destiny.”

Short listening takeaway

  • Personality tests can be fun and useful for team building or self‑reflection, but many popular instruments (particularly those that force binary types or rely on subjective interpretation) are scientifically flawed and should not be used alone for diagnoses, legal decisions, or hiring/firing.