I Took an IQ Test to Find Out What it Actually Measures

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A huge thank you to Emeritus Professor Cecil R. Reynolds and Dr. Stuart J. Ritchie for their expertise and time.

Also a massive thank you to Prof. Steven Piantadosi and Prof. Alan S. Kaufman for helping us understand this complicated topic. As well as to Jay Zagrosky from Boston University's Questrom School of Business for providing data from his study.

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References:
Kaufman, A. S. (2009). IQ testing 101. Springer Publishing Company.

Reynolds, C. R., & Livingston, R. A. (2021). Mastering modern psychological testing. Springer International Publishing.

Ritchie, S. (2015). Intelligence: All that matters. John Murray.

Gregory, H. (2015). McNamara's Folly: The Use of Low-IQ Troops in the Vietnam War; Plus the Induction of Unfit Men, Criminals, and Misfits. Infinity Publishing.

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Special thanks to our Patreon supporters:
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Written by Derek Muller, Casper Mebius, & Petr Lebedev
Edited by Trenton Oliver
Filmed by Derek Muller, Han Evans, & Raquel Nuno
Animation by Fabio Albertelli & Ivy Tello
Additional video/photos supplied by Getty Images & Pond5
Music from Epidemic Sound
Produced by Derek Muller, Casper Mebius, & Han Evans

[mahirnagersheth]

I just took an IQ test and I am SO happy...

Thank God it came back negative!

[tipsbunker]

When I was 8 years old my primary school teacher was convinced that I was gifted because I was always the first to finish a test and because I often seemed to get bored in class. One day I was taken out of class to take an IQ test for this reason. I have no memories of the test itself and no one ever told ma what the conclusion was. Around the age of 15 it also became clear that I had ADHD, despite this I was still holding up in school and I started taking medication. I am now 19 years old and a few months ago my parents told me that I had scored below average on this IQ test in primary school. The primary school psychologist (that had tested me) had told my parents that I would certainly not be able to go to university. My interest in science grew as I got older and when I asked my math teacher last year if I would be capable of studying engineering he said I definitely was. I have now completed my first year at the university.
I am convinced that such IQ tests do not tell the full story at all. I had concentration problems and when I was 8 in primary school I had no idea what kind of test I was even taking.

Don't let some number distract you from your goals!

[gronodon]

Here’s the thing: I used to be a middle school music teacher and went through all the special education and teaching strategy classes. What they don’t tell you is that a student’s IQ generally predicts their success in a traditional classroom setting, and is honestly a pretty poor judgment of individual intelligence outside of that very specific environment.

When I was still an observing teacher prior to student teaching, I was in a music classroom doing recorders and a non-verbal autistic student was participating. As soon as they started their ear training exercises, he was the only kid that got every note right in less than a second and would patiently wait for the class to catch up to him. He had perfect pitch and knew exactly what he was doing, but due to his communication skills he struggled in classrooms that were simply a whiteboard and a lecture. When you gave him a recorder in an open classroom though? He became an extremely gifted young musician who was having a ton of fun and learning a lot!

[ChumblesMumbles]

That bit on motivation, training, test strategy, and anxiety hit the nail right on the head. It can be a very significant impact if all of those are in your favor or if they're working against you. I've been a good SAT-style (multiple choice, timed, reading/math/logic) tests ever since my elementary school started doing state level testing for school districts once a year way back when I was a kid. For me it was just a fun challenge and by the time I ran into standardized tests that caused other people to stress (PSAT, SAT, ACT, LSAT, multi-state bar exam) and actually mattered for some purposes, the "test" part of it was a walk in the park for me, and my only weaknesses were any actual knowledge gaps or making mistakes. Meanwhile I know folks who got immobilized by anxiety or just weren't used to the format had problems with the form of the test even if they had the knowledge down as well or better than me.

I took an IQ test once that had a time limit and there was a clock in the room. I don't like time pressure so I panicked and ended up with a not too bad but still very depressing score. They made me take another test and told me it wasn't timed, I did way better, was proud of myself. They actually lied to me, it was timed, but by not telling me I just got a way better score and still finished in time. So many factors as to why someone would get a bad or good result in a test.

[seijirou]

I was born in '81. I still remember in my kindergarten class there was a poster on the wall that read "It's not your IQ, it's your I WILL". That has stuck with me as demonstrably true my entire life.

[hermesrodrigues]

Your point on child nutrition/education is so important. Ive seen so many altright people on the internet make racist comments based on IQ difference for populations when in fact it just shows that those populations are not having their basic needs met properly.

[rogerstone]

A brilliant, open, honest evaluation of the history and value and uses of IQ tests. Well done, sir. How you resisted the temptation to dramatise it I do not know; but I wish that more TV and other media documentary makers would follow your example. Thank you.

[cupostuff]

It's actually really interesting that the IQ test has a baseline relative to the average of all scores, which means it measures your intelligence relative to others & not some fixed constant.

[JagEterCoola]

Here's a (depressing) little fact about me.
Some decade ago, when I was 12-13, I volunteered to take an IQ test at my school, and was generally considered a 'gifted kid' with outstanding grades in a lot of subjects, as well as an appetite for knowledge that shocked my teachers at the time - Books would be devoured in a matter of hours, I never studied and aced everything anyways because, as it turns out, what I did on my free time (devouring random wikipedia articles, essentially) was effectively studying.

Then, my parents divorced, my grandparents and dogs died, and I went through a maaaajor depressive episode lasting, well, it's still going over a decade later, but the worst of it was age 14-19, where I was actively suicidal.
For 'fun', I took a new IQ test when I was turning 20.
My IQ when I was ~13? 144.
My IQ after a major depressive episode a few years later? 106.
My IQ today, another few years after that? 112.

I don't want to blame depression or anything like that, but I do think it played a very large factor in killing my motivation for study - and notably, it killed a lot of my memory. I couldn't tell you a thing I did age 14-19 with any level of real accuracy other than scream at my divorced mother twice and moving house five times.

[justinlynch]

Man you knocked this out of the park. You really gave this its fair shake. I wish the public discourse covered subjects this thoroughly.

You continue to raise the bar.

[rogerstone]

I like the way, at 2:40, you give examples of perfect negative and positive correlations, and the examples DO NOT PASS THROUGH THE ORIGIN, making a neat point without having to labour it. This is a good channel. Source of endless fascination. (This from someone good at English, poor at Math.)

[BryanBagehi]

My father was a psychologist. Growing up, he regularly administered various IQ tests on me. I became quite competent at standardized testing. To this day, I discount the value of these tests as I know I effectively cheated on them throughout the rest of my life. I learned test taking strategies and practiced the common types of questions so I am able to identify patterns of questions/answers favored in each test, which positively impacted my results compared to many others who did not have this experience.

[realDonaldMcElvy]

I had an IQ of 123 when I was a teenager. I call it the Henry Ford Intelligence Test, because it only measures you like a factory worker.

[dearheart]

It reminds me of the Mensa tests I did earlier on in my life, and how my mind have focused on different areas during life. Like math, physics, logic was a main part of my life until I was teenager, then other things took a larger role.

[ceooflonelinessinc.]

I (33) have a learning disability. My IQ is approx 80. I got tested twice in school. It is mainly due to the fact that my mother drunk alcohol during her pregnancy (FASD spectrum/Fetal Alcohol Syndrome)

Everything is harder in my life. No matter how hard I try, I always fail. I needed to visit special ed class till 18, I never had many friends, I never had the ability to visit college or achive high education, I only work at sign holder jobs...or fast food...I also never had a girlfriend. A low intelligenc is a severe punishment for your whole life, which affects every aspect of your life negatively.

[SmigGames]

I took an IQ test a while ago and I debated a lot about whether to take it, because, if we're being honest, I think most of our motivation to take such a test is to get a result that validates our belief that there's something special about us. A high score can give you a lot of self-esteem and confidence. But the opposite can also happen with a low score, given how many insults we throw around based on IQ and intelligence. It's not likely that knowing this number is gonna be relevant to you other than in this way, so I'm still not sure if most people should test their IQ.

[draheim]

This touched on a lot of areas I have research experience in and I must say it was an excellent, well-researched, video.

Have you considered doing a deep dive into a cognitive training? It’s a quagmire in and of itself with a lot of misinformation, false claims, and predatory marketing approaches (and the tl;dr version is we have virtually no solid evidence broad cognition can be reliably improved, but some evidence narrower abilities can and/or that training might beneficial as a recovery tool).

[Doodelz]

I feel you've addressed questions I've had for most of my lifetime. That's pretty amazing. Thank you! Age-wise, it's too late for me to do anything about it, but that's a "me" problem! 😊

[Marychelle]

One of the worst things that happened to me in my childhood was scoring well on an IQ test as a small child. Severe ADHD and no executive function led to a lot of shame because people had something to point to to “prove” I was just being lazy. Even after I was diagnosed with ADD at the age of ten.
Edit: I turned 10 in 1981 (just for perspective). Neurodivergence in the 70s and 80s was just called being contrary.