The Full English Accompaniment – Psychometrics, Myers-Briggs and the pseudoscience of personality analysis

What’s piqued my interest this week?

I bloody hate the Myers-Briggs Type Indicator, the personality analysis ‘tool’ whose results I keep seeing all over the internet (1). The test beloved of HR departments, taken by 2.5 million people a year, used by 89 of the Fortune 100 (2). It seems to be used as shorthand for various perceived positive characteristics in some quarters, others try to find correlations with the FI movement, while paid-for articles use it to try to guide individuals to their ideal investments (3, 4, 5, 6). I’ve come into contact with it through work, when departments have told me my role in teams through it’s interpretation. Problem is, it’s a load of manure.

Test-retest reliability

The probability that if you resit the same test you will get the same result. Myers-Briggs own website gives figures from 75-90% for this (why the wide confidence interval?) (7). Those figures have been supported by independent research (8, 9). I can’t use a blood test, or any other scientific test, that gets the answer wrong 1/4 of the time on retest in clinical practice. Imagine if I’m checking for an infection, and tell you it’s one thing, only to retest next week and tell you it’s another. So why does it persist in public use? I’ve probably taken the MBTI four times in various setting, with three different results.

Construct validity

Myers-Briggs grew out of Jungian types in the ’40s. Jung’s theories about archetypes, types, synchronicity, the collective unconscious etc, continue to be taught today in psychology, but more as part of a history lesson and a way for people to understand themselves. They’ve been superseded and are considered by most psychologists to be unscientific, with no clear grounding of reproducible evidence (1, 10, 11). So while the Myers-Briggs sorts you into categories, there’s no actual evidence that those categories are based on anything other than theory.

Content validity 

A further flaw is the question methodology, often using black and white variables to identify which category a person falls into. Personality is not black and white. The dichotomous variables used to decide which category you fall into would be expected to result from a bimodal distribution of choices, with most people at either end of the scale. Instead we see a more normal distribution, with clustering around the middle (1, 10, 11). This invalidates the test variables; the reasons behind choices are not dichotomous, but informed by an interplay of your previous experiences, your taught and learnt behaviours and your biological wiring. The chicken crosses the road for multiple reasons, not simply to be on the other side. It’s an over-simplification of a complex construct.

And that’s just for starters. There’s a huge list of criticisms and peer-reviewed rebuttals on Wikipedia (1). Much of the pro-MBTI literature is the product of poor methodology and limited scrutiny. It’s been largely sidelined by the professional community but persists in the mainstream consciousness (12). People want an easy way to understand a complex system, which is probably why HR teams around the world continue to use it, but personality is too complex to be reduced to 16 types. By all means use it as a methodology for personal reflection. Just stop trying to class others.

Have a great week,

The Shrink

Other News

• Manufacturing job losses are at a six-year high (13)
• Gove appears to be doing a good job as Environment Sec, barring US attempts to trade their chlorinated chicken and hormone-fed beef with the UK (14)
• The average mortgage rate has crept up ever so slightly, but remains historically low (15)
• Bulb drop their energy prices as other suppliers increase them (16)
• Speculative article about future classic cars (17)
• Bond yields are gradually climbing (18)
• People are whinging about the cost of their rent-to-own products (19)
• MSCI are tripling the weighting of China in their global benchmarks (20)

Opinion/ blogs:

• Nils Pratley on Aston Martin’s slump and Norwegian investment in the UK (21)
• And this week, on the effects of Brexit beyond the city (22)
• DIY Investor UK takes a look at another renewables fund; TRIG (23)
• And reviews the Uninhabitable Earth (24)
• The Accumulator at Monevator lays out the sums required for the FI journey (25)
• And looks at the Gordon Equation for calculating expected returns for equities (26)
• And The Investor looks at automated Seed Investing through platforms like Seedrs (27)
• MMM pitches a new city (28)
• TEA has a guest post talking about the benefits of being a DINK household (29)
• And encourages everyone in ways they can improve their finances (30)
• The Cashflow Cop details how lodgers have helped him towards financial independence, and rules for being a landlord (31)
• And makes a fun little checklist to test how far you are from FI (32)
• Mrs Frugalwood provides a January homestead update (33)
• John at UKVI measures up BAE systems (34)
• And Unilever (35)
• Ken and Barney are organising another UKFI meetup in that there LDN (36)
• The Caveman lists 12 environmental actions you can take to save cash (37)
• The Female Money Doc on why it’s ok not to be too ambitious (38)
• The Saving Ninja has an EW betting guide (39)
• And provides a ready made EW spreadsheet (40)
• And also updates with February’s number (41)
• Early Retirement in the UK publishes their January numbers (42)
• February update from I Retired Young (43)
• From LMF (43)
• And a February update from GFF (45)
• Plus GFF has posts looking at pensions (46)
• House price inflation (47)
• And LISAs (48)
• Weenie organises a Mancunian meet-up (49)
• Tuppennys Fireplace with 30 cheap foods for a frugal budget (50)
• Fumonchu at FIUKMoney gives their February accounts (51)
• As does Dr Fire (52)
• Indeedably on tax efficiency (53)
• The influences on your choices (54)
• Mortality and the unexpected costs caring of family (55)
• And lessons in delayed gratification versus the joy of spending (56)
• YFG on the importance of making saving a habit (57)
• Plus this great video from The Visual Capitalist (58)

The kitchen garden:

• Tanya at lovelygreens with advice on pricking out tomato seedlings (59)

What I’m reading (affiliate links):

Tombland – C.J. Sansom – I love the Shardlake series, detective novels set in the Tudor period with a crippled lead character. Beautifully written.

Food Of The Gods: The Search for the Original Tree of Knowledge: A Radical History of Plants, Drugs and Human Evolution – Terence McKenna – An ethnobotanist explores humanitys’ fascination with hallucinogenics, and the role of altered states of consciousness on the development of human society.

References

1. https://en.wikipedia.org/wiki/Myers–Briggs_Type_Indicator
2. https://www.psychologytoday.com/gb/blog/give-and-take/201309/goodbye-mbti-the-fad-won-t-die
3. https://www.huffingtonpost.ca/krysten-merriman/myers-briggs-type_b_9877786.html?guccounter=1&guce_referrer_us=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvbS8&guce_referrer_cs=-03q25v6JqVhVASPJTimXg
4. https://www.reddit.com/r/financialindependence/comments/4gky1p/myersbriggs_of_fire/
5. https://www.millennial-revolution.com/build/right-personality-fire/
6. https://forum.mrmoneymustache.com/ask-a-mustachian/intj-folks-has-fire-been-the-answer/
7. https://www.myersbriggs.org/my-mbti-personality-type/mbti-basics/reliability-and-validity.htm
8. https://www.researchgate.net/publication/236111463_The_Myers-Briggs_Type_Indicator_Evidence_of_its_validity_reliability_and_normative_characteristics_for_managers_in_an_Australian_context
9. https://journals.sagepub.com/doi/abs/10.1177/0013164402062004004
10. https://www.psychologytoday.com/gb/blog/cui-bono/201603/are-scores-the-mbti-totally-meaningless
11. https://www.theguardian.com/science/brain-flapping/2013/mar/19/myers-briggs-test-unscientific
12. https://bit.ly/2Upya1b
13. https://www.bbc.co.uk/news/business-47414916
14. https://www.theguardian.com/politics/2019/mar/01/us-seeks-greater-access-to-uk-food-markets-after-brexit-trade-deal
15. https://www.thisismoney.co.uk/money/mortgageshome/article-6742415/Mortgage-rates-begin-creep-lull-price-rises.html
16. https://www.thisismoney.co.uk/money/bills/article-6760015/Bulb-Energy-shames-Big-Six-providers-exploitation-price-cap-cutting-prices.html
17. https://www.thisismoney.co.uk/money/cars/article-6756471/Classic-car-experts-reveal-bangers-worth-banking.html
18. https://moneyweek.com/502897/bond-yields-interest-rates-creeping-higher-why/
19. https://www.bbc.co.uk/news/business-47452571
20. https://www.cnbc.com/2019/03/01/msci-to-quadruple-weighting-of-china-a-shares-in-global-benchmarks.html
21. https://www.theguardian.com/business/nils-pratley-on-finance/2019/feb/28/aston-martin-share-crash-shows-valuing-a-dream-takes-adjusting-to
22. https://www.theguardian.com/business/nils-pratley-on-finance/2019/mar/05/brexit-wont-bother-the-city-but-everyone-else-should-worry
23. http://diyinvestoruk.blogspot.com/2019/02/renewables-infrastructure-new-addition.html
24. http://diyinvestoruk.blogspot.com/2019/03/the-uninhabitable-earth-review.html
25. https://monevator.com/simple-maths-for-investors/
26. https://monevator.com/the-gordon-equation-how-to-calculate-expected-returns-for-equities/
27. https://monevator.com/robot-angels-automated-seed-investing-on-the-seedrs-crowdfunding-platform/
28. http://www.mrmoneymustache.com/2019/02/27/how-to-create-reality/
29. https://theescapeartist.me/2019/03/05/its-easier-without-children/
30. https://theescapeartist.me/2019/03/09/financial-independence-is-for-everyone-part-2/
31. https://cashflowcop.com/my-property-investment-journey-part-1-taking-in-lodgers/
32. https://cashflowcop.com/fi-checkpoint-where-are-you-on-the-journey/
33. http://www.frugalwoods.com/2019/02/28/this-month-on-the-homestead-when-your-internet-and-your-truck-conspire-against-you/
34. https://www.ukvalueinvestor.com/2019/02/bae-systems-dividend-good-value.html/
35. https://www.ukvalueinvestor.com/2019/03/buy-unilever-wake-up-rich.html/
36. https://theescapeartist.me/2019/03/01/meet-up-friday-29-march/
37. https://ditchthecave.com/save-the-world/
38. https://thefemalemoneydoctor.com/ambitious-life-goals/
39. https://thesavingninja.com/ew-betting-full-guide/
40. https://thesavingninja.com/macro-enabled-matched-betting-spreadsheet/
41. https://thesavingninja.com/bring-on-the-summer-savings-report-8/
42. http://earlyretirementinuk.blogspot.com/2019/02/january-end-of-month-report.html
43. https://www.iretiredyoung.net/single-post/2019/03/01/Early-Retirement-Costs—February-2019
44. https://littlemissfire.com/february-2019-income-and-expenses-report-2019/
45. https://gentlemansfamilyfinances.wordpress.com/2019/03/05/month-end-accounts-february-2019/
46. https://gentlemansfamilyfinances.wordpress.com/2019/03/07/pension-payback-prevention/
47. https://gentlemansfamilyfinances.wordpress.com/2019/03/09/house-price-inflation-friend-or-foe/
48. https://gentlemansfamilyfinances.wordpress.com/2019/03/10/a-fire-argument-for-the-lisa/
49. http://quietlysaving.co.uk/2019/03/09/meeting-up-in-manchester/
50. https://tuppennysfireplace.com/best-frugal-foods-buy-broke/
51. http://fiukmoney.co.uk/february-19-net-worth-and-monthly-update-7/
52. https://drfire.co.uk/february-2019-income-expenses/
53. https://indeedably.com/taxes-are-optional/
54. https://indeedably.com/puppetry/
55. https://indeedably.com/filiality/
56. https://indeedably.com/financial-junk-food/
57. https://youngfiguy.com/saving-sucks-or-why-you-need-a-savings-habit/
58. https://youtu.be/BQovQUga0VE
59. https://lovelygreens.com/pricking-out-tomato-seedlings/