Braindump

MBTI, DiSC and Insights Discovery. All of it is nonsense

Prompted by being asked whether he was "a qualified DiSC or MBTI practitioner" — "a bit like asking a surgeon if they were certified in crystal healing."

SourceUpdated 22 Aug 2026

MBTI, DiSC and Insights Discovery. All of it is nonsense

Prompted by being asked whether he was "a qualified DiSC or MBTI practitioner" — "a bit like asking a surgeon if they were certified in crystal healing."

> The common thread: "These systems look psychological, but none of them came from psychologists."

MBTI

  • Created by Katherine Briggs and Isabel Myers in the 1940s — a mother-daughter pair, neither with formal psychology training.
  • Based on Carl Jung's early ideas — which Jung himself said shouldn't be used to classify people.
  • The structural problem: it assumes you can divide billions of people into 16 fixed boxes. "Personality isn't binary. You're not either introverted or extroverted — you exist on a spectrum, and that spectrum changes with context."
  • It forces false choices — do you prefer to plan or be spontaneous? — "as if people don't do both depending on the situation."
  • It fails basic reliability: take it twice and half of people get a new type within weeks.

> "It has the same predictive power as sorting staff by star sign — only more expensive."

DiSC

  • William Moulton Marston — who also created the lie detector and Wonder Woman. "Neither Wonder Woman nor the lie detector are admissible in court."
  • No background in psychometrics, "but an impressive sense of drama."
  • Four types: dominant, influential, steady, conscientious. You take a questionnaire, "and the algorithm decides what colour you are."

> "No validated science. The categories are arbitrary. Test-retest reliability is poor. And the results are self-reported" — "we're paying to have people tell us what they think they're like." "A very efficient way to confirm your own biases."

  • It feels authoritative because of "glossy graphs and colour wheels."

Insights Discovery

> "Essentially DiSC in a different wrapper." Same colour idea — "and they use Jung's name again to lend it gravitas." (Noted as a pattern across these tools.)

The business model: "you sell training licences to consultants, who sell workshops to companies — and everyone profits except the science."

StrengthsFinder

From Gallup. The sentiment — focus on strengths rather than weaknesses — is "lovely," but:

  • No independent validation
  • It assumes strengths are fixed traits rather than skills developed over time
  • "It's popular because it's flattering. No one ever leaves a StrengthsFinder workshop feeling inadequate."

The wider point

Corporate use of these tools for hiring and promotion decisions is the real objection — "extraordinary when you think how many companies use it to decide who to hire or promote." Office life becomes "corporate Hogwarts houses" — colour-coded tribes.

Cross-references