How Much Do Genes Matter?

A reader emailed me after I wrote about learning calculus in five days:

“I question that you’re just a person of average intelligence who knows how to learn faster. I can’t imagine ever finishing an MIT class in 5 days.”

My response to him was that, of course, I was probably smarter than average. If we measure intelligence, in part, by a persons ability to learn quickly, then learning faster than average would imply being smarter than average. He responded back with:

“Would you say someone with average genes could learn a class in 5 days with the right techniques?”

The question doesn’t make any sense, but I feel it represents a common viewpoint so I wanted to share my thoughts here. What on earth does “average genes” mean?

Do You Need Good Genes to Be Smart?

The real problem is that society has extremely loaded definitions of the word “smart” or “intelligence” which tends to preclude any meaningful discussion. Worse, now these loaded definitions are mixed up in people’s equally confused minds about genetics.

I want to clarify some misconceptions:

  1. You can’t have an IQ.
  2. When researchers say 50% of intelligence is heritable, they don’t mean 50% of your intelligence is caused by genes.
  3. Innate talent doesn’t mean immutable talent.
  4. No, not all people are created equal, but that’s true of everything.

“Maybe You Just Have a Really High IQ?”

This first misconception bothers me the most. An IQ is never something you can possess, it is merely the result of a test you have taken. Think of an algebra test. You would never say, “I have an algebra quotient of 120!” So why do people say “I have an IQ of 120”?

It may seem like I’m splitting hairs, but it’s a big difference. IQ is not intended to measure only innate, immutable ability. It also measures knowledge you’ve accumulated through experience.

The way IQ is calculated is that your score is compared to people the same age as you, using a bell curve. So a particularly precocious 10 year-old who scores 150 isn’t necessarily smarter than me.

In fact this sorting by age is often necessary, because otherwise people’s IQs would grow steadily higher as they aged. This only makes sense, if IQ tests also measure knowledge and cognitive skill, then one would expect to score better as you accumulate more experience.

The other misconception about IQ is that it measures general intelligence. I firmly believe that such a scalar quantity does not exist. Studies involving chess grandmasters show that they are not particularly more intelligent in other things than an average person, despite being a genius in chess. Intelligence, it turns out, is highly contextual.

I don’t think IQ tests are useless, and most psychologists who use them understand their strengths and their limitations. The problem is that a misinformed public has grossly exaggerated both their relevance and the idea that intelligence is something you can pin down to a number.

What Does it Mean When Scientists Say 50% of Intelligence Heritable?

Studies generally show about 50% of intelligence is heritable, with the other 50% coming from the environment. This type of research is usually grounded in separated identical twin studies, where the effects of genes and similar upbringings can be sorted.

Now most people take these results and interpret them as saying that 50% of my intelligence is caused by my genes. This is incorrect.

What scientists mean when they say 50% of intelligence is heritable, they are saying that over the population being sampled, 50% of the deviations from the average in intelligence can be explained by differences in genes. This sounds similar to saying your smarts are half genes, but it’s not.

For example, let’s say we took 100 boys and raised them in barrels, where they received no sunlight or human contact of any kind, until they were 15. Then we gave them an IQ test immediately after sending them into the world.

For this population, 100% of the deviation in IQ would be explained by genes. After all, their environments were identical, so it cannot be a factor. However, this doesn’t mean that the boys’ general mental ability is the result of their genes—clearly their environment was the key factor preventing them from being normal.

Scientists cannot, at this point in time, say what percentage of your ability comes from genes. All they can do is observe population deviations. That’s very useful information, but just because 50% of IQ is explained by genes, that doesn’t mean 50% of your individual intelligence is caused by genes.

How Much Do Genetic Advantages Matter Anyways?

This confusion is compounded by another common misconception people have. People hear the words “genes” and they believe this means innate talent. Second, they believe that innate talent means immutable ability. Although these things could be true, they are not logical consequences of each other.

First, what is the difference between genetic predisposition and innate talent? Genes could cause a natural aptitude, in math, for example. But a genetic predisposition could also mean that you simply enjoy math more, so you’re more likely to work hard at it.

The fact that researchers can see trends in populations being explained in heritability does not mean the mechanism of action is well understood.

The second, even more tenuous, jump people make is assuming that if talent is innate (or caused by genes) that it is necessarily impossible to change. This one is demonstrably false.

A really simple example is hair color. Hair color is mostly genetic. But I can purchase a bottle of hair dye for a few dollars and gain nearly 100% control over the actual color of my hair. In this case, the innate attribute of hair color is entirely modifiable by technique.

The same is true of talent. Yes, some people may have more natural aptitude, but that doesn’t mean that you’re stuck with what you’re born with. Even if an attribute was mostly genetic, that wouldn’t preclude new methods from being able to improve that attribute.

My favorite example of this is the running of the 4-minute mile. Before 1954, no human being had ever ran a 4-minute mile. Then Roger Bannister completed his run in 3:59.4. Now thousands of people have completed a 4-minute mile.

Running is something, I feel, has a lot of similarities to intelligence. There is definitely an element of innate advantage; Bannister was an incredible athlete. But the gene pool didn’t suddenly change in 1954. Instead, the new approach allowed other people to push past the barrier as well.

The question I got was whether anyone can complete an MIT class in 4.5 days. I don’t think most people could, just like I know I can’t run a 4-minute mile. But that doesn’t mean that you can’t learn better, just as Bannister’s aspirational marker doesn’t mean you can’t train to run faster.

No, People Are Not Created Equal

Yes, some people have innate advantages over other people. Life is unfair. I’m not trying to spin this article into saying that there don’t exist fantastic geniuses whose abilities are largely unearned.

But it frustrates me when I see people making equally absurd chains of reasoning to assume that because some people have a head start, that there’s no point trying to learn better.

My methods may not turn out to be fully correct. I’ve worked with a lot of students, but I don’t forget that many of my ideas haven’t withstood a barrage of peer-reviewed experiments demonstrating causality. But I do feel that, regardless of your opinion on metaphors, the Feynman technique or flow-based notetaking, that anyone can improve how they learn, just as they can improve anything else.


Speaking of learning faster, I just finished my second week (and second class) of my MIT Challenge to learn MIT’s computer science curriculum in 12 months, without taking classes. You can see the video below where I discuss how you can watch lectures at 2x speed, how to learn math faster and link to free resources I’ve been using:

Read This Next
Should You Know Your IQ?
  • Tassia

    Hi, Scott,

    Thanks for addressing this issue. Many years ago, when I took an IQ test, I was appalled at just how cultural it was. I was lucky in that I read a great deal and had a great memory (no longer the case, alas), but I wondered how many kids had been dubbed not as smart only because they had a narrower world of reference than I did.

    I mean, words like “pied-à-terre” were on there, and back in those days they still had the gall to say the tests weren’t cultural- or class-based!

    Unfortunately, the belief that innate intelligence was acurately being measured is still prevalent in a large part of our culture; it pervades as background radiation and needs to be taken out and examined closely. Far too often, we fail to ask ourselves, “Is that true?” and just accept ‘received wisdom’ as wisdom instead of what it really is: unexamined misinformation.

    There’s probably also a good deal of Fixed versus Growth Mindset going on in the underlying assumptions in the question posed to you. I suffered for far too many years with a Fixed Mindset and am now working on reframing my beliefs (about myself) onto the path of the Growth Mindset. Not as easy as I would like, but well worth the effort.

    I’m enjoying your posts on your MIT learning experience. Thanks for sharing the experience and for showing us the Growth Mindset in action (at least that’s how I see it). Very encouraging!

  • T. Jay Johnson

    Here’s something to add to the topic, a short read and right on topic with your post.

    Hambrick’s response: “David Brooks and Malcolm Gladwell are simply wrong. The evidence is quite clear: A high level of intellectual ability puts a person at a measurable advantage — and the higher the better.”

    Research has shown that intelligence has both genetic and environmental origins, Hambrick said, yet “for a very long time we have tried and failed to come up with ways to boost people’s intelligence.”

  • Scott Young

    T. Jay,

    Undoubtedly genetic advantages exist that certainly set the bar higher. My last section was dedicated to that. I’m not suggesting Gladwell’s environmental determinism (or fatalism) is correct.

    But as to your claim “we have tried and failed to boost people’s intelligence” it really depends on how you define intelligence. You can always load the definition in such a way that it becomes unchanged with respect to technique or practice.

    I’d say, operationally, skills and world-knowledge are the most important consequences of intelligence, and to an extent, a persons ability to learn faster. The first can clearly be improved, otherwise education would be useless as we would possess a fixed knowledge set from birth.

    The second is less obviously true (and some components of learning speed may be constrained, or fixed, by genes), but I would suggest it is also false. For example, if you have better explanations, instruction or teaching, students will learn faster. On a higher-order, if you tell someone *how* to approach a particular topic (not giving them better instruction, but perhaps better meta-methods for instruction), I also believe that they will perform better.

    So, it’s only when you construe intelligence as being an extremely narrow property that it may be harder to change. But most learning isn’t under those constraints–we can create better teachers, education material, meta-methods for approaching the material, etc.

    In short, innate intelligence certainly exists. But just because I may not be Roger Bannister, that doesn’t preclude me from learning to run better.


  • Adam

    I agree with you here. I run in my spare time, and it’s amazing how many people will tell you that running is pointless because all the top athletes are genetically gifted, and so mere mortals such as myself have no chance of becoming so good.

    Of course, that is complete rubbish, for two reasons.

    1) How do you know you aren’t genetically gifted? Until you’ve given running a good shot and proven that your genes are insufficient, how can you say that you can’t be as good?

    2) Even if I’m not genetically as good as the top athletes, I can still get a hell of a long way simply by training hard and regularly.

    I suspect that the real reason isn’t that people really think they are genetically superior, but rather that people are afraid of committing a lot of effort to something and then not being as good as someone or something they were trying to measure against.

  • T. Jay Johnson


    Completely agree that intelligence can be improved (and that we should be trying all the time!). Just shared it to add to the discussion. So far most of those I’ll shared that link with disagree with some part of that study and/or its conclusions.

  • Sarah

    You forgot to mention that IQ tests are written for the white middle class and absolute geniuses from non-English cultures will usually score average or below average.

    One thing that is interesting about genetically identical twin studies are the studies on identical twins and autism spectrum disorder. If you haven’t read up on them before you’ll probably find them really interesting.

  • Leiah

    A question like “Would you say someone with average genes could learn a class in 5 days with the right techniques?” almost sounds like an excuse or advance justification for why that person isn’t succeeding.

    It sounds like “I really want to learn fast like you are! But I don’t believe in myself to do it, and I’m scared that if I try I might fail. So I’ll just blame my failure on my average genes.”

    Just like running, you can be very successful if you believe in yourself and work hard. I don’t think the problem is your genes, it’s that you were raised and shaped by others to doubt your abilities. Believe in yourself and try! 🙂

  • eric

    scott (commenting your video) i know your works is about teaching people how to fish rather than give the fish,but i think it will be nice too if you work something (maybe a book ) on understanding math concepts in the sweet and smooth way like you do.

  • Matt

    Hey Scott!

    Watching videos at a higher speed is a good tip – unless the person already speaks fast 😉 In that case, you’re limited to 1.5 times or so. Did you have to adjust the rate based on the person’s rate of speech?


  • Karan

    Exactly. I think most intelligence is just about believing that you can do it.

    Same is the case for talent: some people understand subjects better simply because they’re much more interested in mastering the subject.

    I also think most learning ability is all about fascination and interest. I built a telescope at age 8 (a newtonian reflector) and assembled a PC at age 12… This doesn’t mean I’m smart. I could do that simply because I was interested and fascinated by compyters and the night sky.

  • Phil Drolet

    Hey Scott,

    Another perspective you didn’t discuss is that of neuroplasticity- the brain’s ability to rewire itself, to create new neurons & synapses based on the stimulus we give it.

    Effectively, the brain is like a muscle- with proper technique we can train it. In the book “The Brain that Changes Itself” there’s tons of examples of people who had bad genetic dispositions or cerebral injuries who were able to train their brain to a level higher than the average.

    For those looking to hit the brain gym, I highly recommend checking out They have some great brain training games that are both fun & effective.


  • Sara

    Some psychologists actually did research on IQ tests, where they found that black US students did worse than white US students. This was in the 60s or 70s, iirc. When they reworked the test, to seek the same underlying concepts to be demonstrated – manipulation of data, understanding of concepts, etc. – but geared towards the social/cultural experiences of the black students, the results reversed.

    Totally in agreement with you here. I was always one of those annoying kids who did well at everything – maths, spatial reasoning, arts, languages, sports. I also benefit from having a pretty strong memory.

    I even managed to score 98% on a biology test, despite missing all the lessons on the material before the test itself. Did similar taking the prep tests for A level sociology and other subjects (the UK exams you take at age 18). But it wasn’t that I was particularly smart, it was just that I was willing to use all my knowledge to look for what seemed to be the most plausible answers. I didn’t panic because I hadn’t had a lesson on it, or give up because I’d missed the classes.

    At other times in my academic career, my grades did fluctuate and go down. It wasn’t that I’d suddenly become less intelligent, it was that the material was more demanding and I hadn’t paid it enough attention, or because I just got lazy and gave up on seeing it as a challenge.

    Changed that, and all went back to normal again.

    I’m finding this site really interesting to visit, because sometimes you’re articulating things I did without fully understanding them (metaphors, etc). Other times, you’re suggesting thing I just hadn’t thought of.

    As an e.g., I really appreciated reading your articles on financial management. It’s an area where I’ve always struggled, and it was really refreshing to have someone else tell me to apply various techniques I’d used in other areas to that area also. Very useful, and it had to come from someone else, to break through the mental block I’d set up for myself in that area. I’d just written myself off as “bad at that” and needed a wake up call to remind me that belief doesn’t fit with my general beliefs about intelligence and competence.

    So, kudos for doing this course. A newcomer to advanced study techniques would surely fail if they tried to follow your example exactly. But, with work, they may get to a point where they can do this. At the very least, it is a stark example of how much we can improve technique to cope with the demands of learning all the way through life. Best wishes for the rest of your course.

  • Anders


    Great post!

    I would highly recommend that you read (and the readers of course), Robert Sternberg’s “Succesful Intelligence: How Practical Intelligence and Creative Intelligence Determine Success in Life”, and “Flourish” by Martin Seligman. The books look at intelligence from a more holistic perspective, and it’s just thought-provoking research.

    For instance, in “Flourish”, there was one study where students were given a GRIT test, testing students GRIT behavior from a scale from 1-5, 1 being very lazy and inactive, and 5 being very disciplined (you can find the test here:…, and correlated it with SAT scores. They found the people with the highest SAT scores were the ones with the highest GRIT scores. They also correlated it with IQ, and found GRIT to be a much better predictor of the scores (and some other parameters).

    Interesting stuff, because it really shows that if we get over the ‘Fixed Growth’ mindset, we are able to achieve great things. The question the student wrote to you seems a classic example of poor confidence. He is does not trust himself enough to fail, because he is afraid of failure. Students that are praised for their great intelligence early on actually do not like to tackle harder problems because they don’t want to look ‘stupid’, but students that are praised for their hard-work will tackle them, because if they do not get the right answer, they’ll just work harder.

    Either way, great discussion, and keep up the good work.