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Tacit knowledge is more important than deliberate practice (commoncog.com)
344 points by shadowsun7 on June 10, 2020 | hide | past | favorite | 128 comments

I figured out something very similar in flight school. When I did my instrument rating, I realized my instructor, Sean, wasn’t perfect. No pilot is. But, I believed he could pass an instrument check ride. I could not.

I decided that rather than figure out if everything he did was the best way or “worked for me”, I would just do my best Sean impression. I still had the opportunity to get even better by learning from other instructors or coming up with my own ideas. That could wait until after I got my rating.

He actually noticed. At the beginning of an early lesson he showed me his check routine during taxi. He flowed through all of the instruments and controls. The next flight, I did my best impression. It wasn’t perfect, but it was close. When I was done he told me no student had ever gone through the whole thing the next flight. Most don’t even try. Even the better students just grab a few things and end up with a routine close to his by the end of training.

It all ended up working. I passed my check ride with just about the legal minimum amount of training time.

Writing this all out and talking about what a great student I was feels pretty egotistical. Ironically, that’s the opposite of what this method is about. Just copy the closest person next to you who is better than you. They don’t even have to be that great. Then, find someone better, and copy them. Save breaking new ground for later in your journey.

Hmm. I think I have a similar story. I was a competitive ballroom dancer, and at one point, a fellow dancer was trying to teach me to have better frame. (Frame is some mix of good posture, being rigid but not stiff; the follower in a ballroom dance uses it to know where to go, and to know what the leader of the dance wants to do. Of course.) I don't think I really got it until at some point he led me (to demonstrate his frame, and how it should feel) and that was what really made it click for me. In an instant I was a better dancer, but I don't think words alone would have gotten us there. Imitating him made me better. (And he had to show me how to lead by making me follow him, and I definitely still have no real idea how to follow, so it was doubly impressive that he got the point across.)

And frame in general is one of those things that when instructors teach, is taught not only through verbal description, but through actual interaction with a person body. (E.g., we pair dancers off, and have them "move" each other using their frame.) And I don't think it could be adequately conveyed with only words, or, it's definitely much easier to demonstrate by physical contact. (And it's one of those things that instructors will critique from the very beginning until … well, if there is a point where one's frame is perfect, I've not hit it.)

The article also reminds me of when I was a TA for Computer Science. Some students need help, in the sense that they need some concept explained better, or they don't know what function or type to apply or don't know a particular data structure. But some students need help, in that they seem to lack something extremely fundamental; the closest I've come to it is that they lack the ability to establish a mental model of a program and how a computer might execute it that is coherent and consistent. (That is, they'll have some rules, but they're more like patches and bits of understanding and are sometimes even self-contradictory, because they the student are closer to grasping at straws than having some idea of what is actually going on.) Getting the student past that hurdle is something I struggled with as a TA. (I myself either picked it up so long ago I take it for granted, or it came naturally. But neither does any good when trying to teach it.) I feel like at some point I read a research paper that seemed to establish that this divide between CS students was the lack of a good coherent mental model, but I've since lost any reference to it.

You're referring to this: https://blog.codinghorror.com/separating-programming-sheep-f...

I was also a TA for CS, for three years, and when you're in that situation and encounter so many students in such rapid succession, the existence of a double-hump becomes really obvious. It's just that because these courses are self-selected, the second hump has a small number of people.

Reading through the linked retraction at the top, it appears it was only retracted for the controversy and claims outside the original findings, not because what it found was false. So it's really frustrating that people use this as a claim there's no such thing.

I can definitely imagine the cause being something like tacit knowledge that we just don't know how to teach, though.

I think you might be right, and interesting, I did not know it had been retracted. Is the retraction trying to retract some claim that people who lack a consistent model are incapable of programming, or something more? (As my original read of the paper was more that the lack of a consistent model was the cause behind poor performance, but not an unsolvable problem, and more of a great hint as to how we could or should approach teaching CS. However, while TA'ing, I did occasionally notice such a behavior, and tried to point it out to the student, and that in and of itself turns out to be harder and trickier than one thinks to communicate, like trying to describe the color blue to someone who hasn't seen it. And, of course, TA'ing is hemmed in by the real-world constraints of too many students, too little time.

> It's just that because these courses are self-selected, the second hump has a small number of people.

By second hump, you mean the weaker group (the "inconsistent" group, from the papaer)? At my college, the early CS classes — which was where I spent most of my time as a TA — were also taken by some students of non-CS majors, as some majors required two semesters of CS. (These were primarily major whereby one might need to say, write a computer model to help validate/invalidate something more related to one's field.) So, they weren't all their completely voluntarily, I suppose?

But we definitely had some self-selected students, those who had clearly been self-teaching themselves computers and programming from early in their teenage years. However, our college also permitted one to voluntarily skip one or both of the first two semesters, if one felt one was strong enough to do so. (There was a grace period at the start of the semester whereby you could still transition between the classes, if you found you had bit off more than you could chew.) So, those clearly strong students who had already been independently studying in the field prior to university could skip over some of the courses.

I like your choice of phrasing on “impression”. I think it captures what is meant by embodiment, that the knowledge is in the body, so you can get at it by imitating the whole of a person.

Thanks. I think it’s much more effective to copy too much rather than too little.

Some people who learn to speak foreign languages fast seem to do this. They copy a native speaker exaggeratedly, almost to the point of parody. And of course young children learn in the same way, by imitating everything rather than trying to filter for the "relevant" bits and imitating those. Most of us are too self-conscious to do this properly though.

Ah, interesting. Back in my presentation days, I found that, if I pretended to be a fire and brimstone preacher when I practiced speeches, and dialed it back when I actually gave the speech, those speeches went a lot better, and were better received.

I'm really good at accents because I imitate exactly. People think I'm a native when I say hello then I can't understand anything after that because I'm really bad at remembering vocabulary.

It's kind of scaring me off moving to another country to learn the language because I struggle to remember words in English. At the same time I know I would master the words and phrases I do learn plus I've always wanted to try being immersed in another culture. Terrified of not being understood I guess.

lol this is me with Spanish. I say common phrases with all the details right, so people think I know more than I do. I actually speak better than I understand.

A big problem is that novices don’t know which parts need to be copied and sometimes don’t even notice what they are missing, so without either (a) getting a decent amount of expert feedback or (b) extensively reasoning things out from first principles and then doing a lot of trial and error, it’s easy to copy extraneous elements or skip essential ones.

A lot of methods and devices that we end up stuck with today in various contexts are just watered down copies of things that were once great, because all of the superficial features were slavishly copied by multiple generations of people who didn’t understand the original constraints or think about which ones have remained constant and which have changed.

If you go from non-functional to functional with extraneous crap that’s a success. Unless you’re working at the forefront of research or at the absolute limits of your capabilities an explicit mental model of what you’re doing is of surprisingly little use. Even that exaggerates how useful it is. The huge majority of improvement is by trial and error, with shoddy and incomplete mental models.

Your last paragraph is just what happens when there’s no force demanding quality. If there’s not strong pressure to maintain or improve quality decline is inevitable.

There’s a really wonderful book called, “The Inner Game of Tennis”, and both your story and commoncog’s essays on pattern matching remind me of it.

This is how small children learn. They copy first, understand later, sometimes very much later.

Not only that - they prefer to copy slightly older kids (closer to them in ability) rather than adults (who are doing things they have no change of reproducing).

You never become exceptional this way. And if you run into situations you’ve never seen before, it’s harder to react competently. With coding, if you only ever use a style you copy, then everything looks like it could be solved in that way. This works and may help you up the corporate ladder. But it will never produce massively positive results

If you copy enough styles then you will eventually see the connections between the styles and come up with your own. This is exactly how you become exceptional, by copying the best over and over again in as many styles as possible until you 'get it'. You have to think about it and understand it too but that comes naturally to anyone who is capable of becoming exceptional, that's the seeing the connections part.

Counterpoint: the better you get at copying, the faster you accelerate your ascent towards being exceptional. Copying is generally the beginning, not the end. By this anti-copying logic, practicing scales on an instrument shouldn't have any bearing on playing a complicated piece of music, only playing that piece, right? And yet, practicing scales until they're perfect and mastered pays dividends because the closer they get to second nature the more firmly they can serve as a foundation for second order skills.

Learning how to copy things is an art in and of itself. A lot of engineers (myself included) got into the craft by taking things apart and putting them back together again. It's true that you cannot become a good engineer /only/ by doing this, as at some point, you must learn how to create things from scratch that you've never taken apart and never put together before. It's true that teaches you a lot, but I think it's a little bit of a stretch to imply that it's the only thing that can teach you.

This method won’t get you exceptional on its own. That’s for sure.

I’m not saying to pick one person and blindly follow them forever. It’s just a really fast way to get competent. I used the same technique to learn programming, scuba diving and sales. After you get the super basics down, find more teachers to copy and start even thinking for yourself a bit more.

It will take you surprisingly far, though. One thing I didn’t mention is it’s good for getting the most out of people who are master practitioners but not great teachers. Rather than ask them to take their skills and package them up for you, you just look over and make a copy for yourself.

As a description of the limits of this strategy, your assessment is probably accurate. This is a reasonable strategy for developing common competence. Whether that means you should adopt it probably depends on where on the relevant competency curves you are -- or how uncommon the competence around you is.

That may or may not be the case, but note that there are many (most?) domains where the positive payoff is bounded, but the negative payoff is not. This method seems particularly useful for those scenarios -- if you have "adequate" performers to copy from.

Instrument flying is actually a great example of this. There are no instrument flying competitions. Well, I guess there’s one every flight. First place, you make it there. Second place, you diverted. Third place, you crash and probably die.

I wonder if the OP post has more to do with nerves/confidence than learning. By imagining he was Sean, he felt confident and the naturally performed better at the job at hand.

To answer your point, there are times in the "learning curve" you need to get used to doing something, and then times to become exceptional. Compare learning to drive to formula 1. And commongcog has an article for that: https://commoncog.com/blog/get-numb-get-good/

Yeah, I think there are issues that fall away when you stop trying to be good and just embrace pretending to be good. Confidence is one of those. I also think a lot about evaluative mindsets versus learning mindsets. Copying puts me in learning mode.

Wow. I have never really given this subject much thought.

In thinking about it, it seems an important part of teaching tacit knowledge is to establish, or cause, conditions that encourage the learning — the experiencing — of the specific things you want to teach.

Thinking back, I realize my own example of successfully teaching tacit knowledge was when I taught my son the first part of how to drive a car with a manual transmission: getting the car moving without killing the engine or burning up the clutch. I took him to a large level area, a huge parking lot, and told him he can do whatever he wants as long as he never touches the throttle. It only took a couple of hours before he had mastered knowing exactly how to modulate the clutch "bite" so that he could get the car moving without stalling, even with the engine at idle. That the car was an older Toyota Corolla with very little torque only helped him better master the finesse required to release the clutch exactly as needed.

We then moved on to modulating the throttle and clutch together, shifting, starting out on hills and all that but, by then, he already knew how to deal with the dark art of the clutch.

I do something similar with guitar. I can teach chords and notes, but I can't teach you how to hold the strings down properly in the first place. "Go play with this until you make the notes every time without a buzzing sound" basically.

I wish I could gift my callouses to beginners. It takes some time to build solid finger tips that can fret consistently at different angles, at the most discouraging part of the learning curve.

>>> He gave me a long explanation about software engineering principles. I waved him away and asked how he did it in five seconds. He said “Well, it just felt right. Ok, let’s go to lunch, you can fix it afterwards.”

Yes. I do a lot of coding on feel, and just today was explaining why something could be done one of two ways but one was better. It took about 30 seconds for my concious brain to work out why it was, even though my unconcious brain knew it straight away.

Weird. Try getting that in an expert system (which might be why they never took off).

And of course try getting that into a CDN without equivalent of twenty years practise.

How do we label good and bad business decisions? Every day?

(side note: actually this is a serious thing I am hoping to work on next year. I think the next big stage of human computer work is computer coaching or feedback on our behaviour. Easy things like our spending habits but heading towards coaching on interpersonal actions - could we for example film a great manager day in day out and identify their activities - and then get them to label the actions - who they spoke to who they encourage why they took that negotiating stance. Do it enough times and you have a real training base.)

I totally agree with this. I think the best engineers are the ones with both a strong "feel", but also a keen ability to introspect, explain, and justify their instinct. The other key ingredient is knowing when to let your intuition run wild, and when to apply it like a seasoning.

On your side note: I also agree here, though the problem may be intractable, since really good managers are not always accustomed to explaining whence their intuition comes.

So much of coding and seeing good and bad design patterns is unconscious pattern matching and unconscious heuristics. I have the same experience of trying to put into words why one design pattern is better than another and it definitely is frustrating because from experience I do have a tacit "feel" about why something is wrong but to convey that to someone else is a challenge.

Would we call that "intuition"?

yeah, but we want to analyse this - is my intuition same as most other 20 year experienced coders? Is it good / correct intuition? is it transferable - can I see same patterns in a different language ? how far away from one language do we go before it breaks down (ie php -> python > java > clojure.)

So many amazing thoughts in this article that apply to the world of software engineering.

If tacit knowledge is as important as the author makes out, then hiring "young guns" is always going to have a cost over hiring people that have done it before. As an older developer, that's interesting to me. A contrary point, however, is that maybe all businesses are new domains of exploration, so you might as well pay the cheapest person to develop your domain specific tacit knowledge.

If tacit knowledge is not something you can get by reading, then training and mentoring is much better (dare I say vital!) than documenting it all in a wiki, or just making sure everything is done asynchronously in a well written pull request.

If tacit knowledge is that important, then getting it is a privilege. If you are in a position where you can be paid to develop those skills and don't just have to read up in the evenings after your kids have gone to bed. Many people don't have that privilege but the software industry prides itself partially on the idea that you just have to self teach yourself; if you aren't doing that, you won't be successful in your job. Tacit knowledge is not that.

All software has two domains of tacit knowledge. One is the domain where the software is applied, one is the knowledge of how to build software that maps to requirements.

You'll always pay for acquiring the applied domain knowledge, you can save on paying for the software engineering knowledge acquisition.

If you're smart, you have both a senior and a junior engineer so you can transfer the software domain knowledge, because acquiring tacit knowledge by working under a knowledgable expert is... not free, but close to it.

If tacit knowledge is not something you can get by reading, then training and mentoring is much better (dare I say vital!) than documenting it all in a wiki, or just making sure everything is done asynchronously in a well written pull request.

This is a weird thing to argue. Productivity could be something like [system-knowledge] X [tacit-knowledge-of-programming] so just tacit knowledge wouldn't get a team maximum productivity.

Altogether, it seems like what's tacit in programming or tacit in any complex domain is "how to integrate different complex and sometimes contradictory things". It's important but hardly important in a "you can discard everything else, this is the magic" sort of way.

I agree with you.

But, tell me if you think I'm wrong: I'm arguing that most software companies have a mentality like you describe: "you can discard everything else, this is the magic" about wikis, PRs (so they generally ignore mentoring and training, or at least don't want it on their employees schedules).

I think you are saying I'm saying that I think that mentoring and training allow you to throw the rest away. I'm not saying that.

It's also worth bearing in mind that tacit knowledge can lead you astray. And that tacit knowledge can be developed without having to be in the same room as someone. It's just that it's learned and communicated _differently_ than explicit knowledge.

I think there's room to explore in the area of building exercises that try to build this tacit knowledge. Though some things are prohibitively expensive to learn outside of a work context. There are definitely a lot of things I've learned in a work context as a software developer that would have taken a lot longer to learn on my own.

That's an interesting view.

How can tacit knowledge be learned without being in the same room with someone ?

To go with the OP analogy: you can learn to ride a bicycle simply by trying, and having seen others ride bicycles.

The tacit is in the fact that trying beats explanations because there are so many variables to account for (eg balancing, how it feels to balance and glide will be different for everyone due to their limbs being of different length, their center of mass being different, their level of fear being different and whoknowswhatelse).

It seems we rediscover Gilbert Ryle's knowing-how vs knowing-that distinction every few years.

https://en.wikipedia.org/wiki/Gilbert_Ryle or if you are so inclined


Note: if you have a computer and it can be "told" once and forever remember it, then converting know-that into know-how by teaching it 100s of if-then rules was, at one point, considered a worthy research program.

It's funny that several thousand words that laboriously reinvent the wheel about tacit knowledge could be summed up in a handful of words of declarative knowledge.

If, in a mood of theoretical reflection, you make articulation in written or spoken language the criterion for "knowledge", it comes as a disappointment to think of all of the cases where we speak of someone knowing something (e.g. how to ride a bike) even though they are unable to train someone to do so entirely verbally (e.g. by written instruction, or over the phone).

But adding the epicycles of "tacit knowledge" and "rules followed unconsciously" clarifies nothing. The mistake was in the overly restrictive definition of "knowledge".

I've surveyed some of the critiques of the "tacit knowledge" concept in this article:


Are you familiar with the Recognition Primed Decision Making Model, or the field of Naturalistic Decision Making? NDM is a field of research that focuses on taking expert intuition (which I refer to as tacit knowledge in this piece), extracting it out of the heads of professionals and then creating training methods to enable less skilled operators to learn these tacit skills on their own. The methods are primarily associated with and deployed in the military.

I think the most famous paper from this tradition is Gary Klein and Daniel Kahneman's A Failure to Disagree, which lays out the conditions necessary for expert intuition: https://www.fs.usda.gov/rmrs/sites/default/files/Kahneman200...

(The two are intellectual rivals, but they put aside their differences to write this piece, over a period of about 6 years, IIRC.)

If you want to get at a definitional debate about the computing applications, that is fine by me. If you want to argue about the philosophical problems with Polanyi's formulation, that is also cool. But understand that I don't particularly care for either debate. I am interested in instrumental outcomes. The discovery of tacit knowledge and the methods found in NDM have been incredibly useful to me in the pursuit of skill acquisition. This was mostly what I was getting at in the post.

"I am interested in instrumental outcomes. The discovery of tacit knowledge and the methods found in NDM have been incredibly useful to me in the pursuit of skill acquisition. This was mostly what I was getting at in the post."

Yup, no worries, I think it's a fine post in that regard. Just trying to separate your genuine insights into the practical problems faced by individuals with a certain social position (knowledge workers, aspiring entrepreneurs), and more general theories about the evolution of labor markets, technological change, and the political consequences thereof.

"NDM is a field of research that focuses on taking expert intuition (which I refer to as tacit knowledge in this piece), extracting it out of the heads of professionals and then creating training methods to enable less skilled operators to learn these tacit skills on their own. The methods are primarily associated with and deployed in the military."

I am only glancingly familiar with this work, but I think you've summarized it well. This basic project - of formalizing work procedures to allow for a shift in the relative amount of skilled versus unskilled labor input to a process - can be traced back to the dawn of the industrial revolution. Gaspard de Prony, Charles Babbage, F.W. Taylor (of "Taylorism" fame), and Herbert Simon (cited in the Klein/Kahneman paper) were all essentially concerned with this question. Harry Braverman and David Noble wrote interesting social histories on this theme, describing how this problem came to be seen as important, and how structuring work in this way - though it was eminently reasonable in the sort term for individual technical decision makers - might have deleterious effects in the long term for society as a whole.

In a way, your recommendations give voice to the desire of many knowledge workers to return to a model of skill acquisition that would have been familiar to the members of pre- and early- modern guilds. Apprenticeship and on-the-job experience was valorized over the "book learning" of "schoolmen".

I just realized that Klein and Kahneman conditions are a good argument for apprenticeships in programming.

One condition is that the you get quick feedback about your decisions. For example, if a surgeon makes a mistake then blood splatters. In programming, if you make a syntax error the compiler immediately complains. However, a design mistake might only bite you months or years later. That is a big obstacle for developing an intuition. However, if an apprentice programmer makes a design mistake. His master can give quick feedback.

I can imagine that the lack of such feedback not only results in slower learning. It might mean the non-apprentice programmer is unable to ever acquire an intuition for design no matter how many years of experience.

> I can imagine that the lack of such feedback not only results in slower learning. It might mean the non-apprentice programmer is unable to ever acquire an intuition for design no matter how many years of experience.

Yes! This is also worsened by the fact that changing jobs frequently is so common. This makes me appreciate my first job, where good design was a priority, so much more.

Reminds me of the "Duke of Hwan and the Wheelwright" by Zhuangzi, from Chinese philosophy; a wheelmaker can't tell you exactly how much force to apply to a wheel or the experiential parts of wheel making, you have to do it to be skilled.


It seems like an arbitrary restriction that training needs to be done verbally. Why not visually, as in slowly riding your bike to demonstrate how to do it?

Misleading title: the thesis is more accurately “Tacit knowledge is why NDM methods are more useful than deliberate practice”.

It also doesn't actually do much to explain that thesis, dismissing delivered practice with the quick an for shallowly-addressed claim that it only works in field with established pedagogy, which may be the case, but most of the fields that it dismisses deliberate practice for on this basis have established pedagogy (with, sure, some pedagogical controversies, but that's true if the field that it acknowledges have the requisite established pedagogy for deliberate practice, too, so it's not at all clear what, if anything, the distinction being drawn is), and doesn't actually do much to establish that NDM methods are particularly useful for developing tacit knowledge. Basically, the piece is an extended discussion of the idea of tacit knowledge, with the whole primary argument, to which most of the piece is only tangentially relevant, rushed through at the end as if it were an afterthought.

> dismissing delivered practice with the quick an for shallowly-addressed claim that it only works in field with established pedagogy

This is the actual definition of deliberate practice. As in, Ericsson explicitly says deliberate practice CAN ONLY exist in domains with a long tradition of pedagogical development.

Go and read the original papers by Ericsson. Or the Cambridge Handbook of Expertise and Expert Performance. Or his popular science book Peak.

One of the nice things about writing a blog is that you get to bring an audience along on a journey of discovery. In this case, you don't actually have to go very far — the blog has done the work for you. This is a 5k word-ish summary of Peak: https://commoncog.com/blog/peak-book-summary/ ... and this is a 5k word summary of all the criticisms arrayed against deliberate practice, also linked from the piece above. https://commoncog.com/blog/the-problems-with-deliberate-prac...

If you want to read about NDM techniques — surprise, surprise! It turns out that the techniques are described in about 10k words over at https://commoncog.com/blog/putting-mental-models-to-practice... and https://commoncog.com/blog/putting-mental-models-to-practice...

And those posts are also linked from the piece.

(Edited to remove snark).

Thanks for the pointers! Not original commenter, but familiar with the literature a bit. One thing that confused me reading your article is that you are criticizing one, fairly narrow way Ericsson has defined deliberate practice.

But in Hambrick, Campitelli, and Macnamara's volume on expertise, they do a good job showing that he has not been consistent with definitions (e.g. 3 definitions: must have, sometimes must have, doesn't require a teacher).

Not a problem for your post, but I was pretty confused about what you were calling deliberate practice until reading this response.

I think there is room for nuance here. True deliberate practice is easiest to apply in those domains, but there are some lessons from Ericsson's work that can be applied using the NDM framework. I think the point that people miss often is that it is deliberate practice, not just practice. While we may not be able to practice like a potential chess grand master, we can deliberately challenge ourselves and look to learn from our mistakes. If you squint hard enough, some of what Klein writes about in "The Power of Intuition" seem like attempts to deliberately practice something in a field without that long tradition of pedagogical development (or fields that don't train for tacit knowledge). His paper with Peter Fadde, "Deliberate Performance" also talks about this. That said, you sometimes don't learn the right lessons, and if the situation changes too dramatically, all your tacit knowledge might work against you.

One tangent comment to go with this: One of Klein's occasional coauthors, Robert Hoffman, co-wrote a book on expert weather forecasters that I really liked. Weather is hard to predict, but one thing they found that what the best forecasters did was to look at the data before looking at what the computer models predicted. Once they had an idea of what they thought the weather might look like, they compared with the model. This kept their skills sharp and ensured that they continued to learn.

In Peak, Ericsson seems to finally settle on one definition, which was what I used in the end. He calls what you just describe "not being able to deliberately practice like a grandmaster" a completely different thing — purposeful practice.

There's a whole chapter in Peak where he tries to talk about what to do if you are in a field with badly developed pedagogical methods. It's basically a badly written copy of The Power of Intuition (Klein). I was incredibly dissatisfied with it, because I was mostly interested in putting DP to practice, and his recommendations were far from practicable. I wish he had just referred to Hoffman or Klein, both of them practitioners in NDM, and therefore both more familiar with attempts to design training programs for fields where no pedagogical rigour exist.

I know you're inclined to give Ericsson a pass, and pass things off as deliberate practice even when his definition clearly excludes said thing. But my view is that we should call a spade a spade and use the exact definitions the man used. If he thought it was good enough for his popular audience, it should be good enough for me.

That makes sense, a couple of years ago there was a lot of misleading interpretations going around, precise definitions help clear things up. I read Peak a while back, and I must’ve forgot that distinction.

I found the Klein book you mentioned more useful than Ericsson’s as well, that Fadde/Klein paper I mentioned was also pretty helpful. I need to reread both, and put them into practice more than I have. I read too much, and I don’t get the tacit knowledge that comes from experience...

Another good book is Surpassing Ourselves by Bereiter and Scardamalia. They studied how students developed writing skill. Their definition of expertise is a bit different than Ericsson’s, but I think it is more useful.

Thanks for the recommendations! Adding to my toread.

Teaching college students how to program my first year of grad school, I realized that it's not possible to make someone understand something. In a real sense, I could not teach them to program. Learning how to program is learning a new way of thinking, and there was no way I could force them to start thinking in this way. I was more trying to guide them to have many personal epiphanies - through a combination of socratic method style questions and giving them specific actions to try with the hope it would improve their mental model.

Exactly my experience slowly learning to code as an adult. My partner sometimes explains a programming concept to me that just won't sink in.

After some practice and time, I can feel my thinking rearranging itself around the concept until it's second nature. Personally it's a feeling I enjoy, part of the reason I like taking up new hobbies all the time.

Tacit knowledge is what I've always thought of as "intuitive feel". As you grow in experience in a field, you start getting this feel for what will work and what won't work. This can be a great advantage, or a great disavantage. I had occasion to work with a fairly bright scientist. He said the reason that most great discoveries were made by relatively young people is because they hadn't developed these prejudices yet, so were unaware that it wasn't suppose to work this way.

Nice article! I guess it's obvious in retrospect, but I hadn't known of all the systematized study devoted to this topic. I'm happy to learn about it because I've found myself thinking about effective teaching and learning pretty often (I'm an academic), and what to do about "the stuff where, when you try to explain it concretely to someone else, your explanation doesn't really make sense unless the other person already knows what you're talking about".

In subjects I've tried to learn and teach, my experience is that talking to someone with a lot of such knowledge really only gives you an idea of the sub-topics and considerations you should try to understand better on your own. It is helpful in narrowing down what you should prioritize and maybe giving you a useful point of view to organize your thoughts from, but that doesn't save you from doing the thinking and understanding for yourself.

I agree that emulation helps somewhat by forcing you to make choices that are reasonable even if, as a beginner, you lack the knowledge to choose wisely yourself. But if the ultimate goal is to come up with new ideas using the knowledge, I think there's such a thing as too much emulation. You don't want to become a carbon copy of your mentor either.

I agree that deliberate practice and acquiring tacit knowledge are not the same thing. To me, deliberate practice is about repeating a certain activity -- one that you typically can describe in words to someone who doesn't already know it -- enough times that it's available to you as a tool, eg playing scales as a musician, times tables in elementary school math. Tacit knowledge has more to do with how you decide to apply those skills to best effect.

But my experience has been that they have kind of a symbiotic relationship. If you didn't have some tacit knowledge to begin with, you wouldn't know what to practice, or when you had practiced enough to be good. At the same time, it may not be possible to acquire enough tacit knowledge to become an expert if you don't have an immediate command of certain skills developed through deliberate practice. I.e. there's feedback -- more tacit knowledge should make your deliberate practice more effective, and better skills make it easier for you to acquire tacit knowledge.

The reason tacit knowledge exists and is essential is because the brain is immensely complex, and most of what it does is outside consciousness.

To take just one well-studied example, in vision photons hit visual receptors in the retina, and then go through the optic nerve which is a complex computer that analyses the signals in stages, like picking out points, then lines, then shapes, and so on, and then it is sent to several different visual areas of the brain, each of which pulls out different features, like motion, colors, 3d shapes, faces, and emotional expressions, and then finally it arrives in consciousness. Something similar is true for every other sensation, and how they are integrated to give us our perception and understanding of the world.

As a consequence, children from birth learn all sorts of things without explicit instruction and often even much focal thought, include the great majority of the rules of language itself.

All of this is subjectively experienced as a sort of feel or intuition. It is described by philosophers such as Michael Polanyi and various phenomenologists. I studied with one of them, Eugene Gendlin, who developed a method called experiential focusing for helping people make use of their tacit knowledge (he called it felt meaning). You might want to take a look at his book Focusing.

One more point. The idea that all knowledge can be clearly explicated is an example of the denial of human finitudes that is common in much of Western philosophy, but that are affirmed by other schools Western philosophy, such as pragmatism, existential-phenomenology, and post-Wittgensteinian analytic philosophy.

This is interesting. Wittgenstein argues that this idea of 'tacit knowledge' has no meaning. What the article describes is practice.

'My point is that their explanations would not lead me to the same ability that they had.' is a very Wittgensteinian thing to say. See i.e. the parable of the wayward pupil in the Investigations on what role understanding/practice even play in the context of a statement like 'would not lead me to the same ability that they had'

'But the more I pushed, the more exceptions and caveats and potential gotchas I unearthed.' W argues that this is a result of our concept of what it means to understand. Can you name an idea where this doesn't hold? W uses a great example of your knowledge of the Natural Numbers. Just because you hadn't thought of the number 10324 beforehand, does that mean your knowledge didn't encompass it? Before you attempt to foist the problem onto mathematical logic (it doesn't work, but the answers become longer than an HN comment) consider your concept of the color 'red'. What shape is it? Did you a prior have in your mind the shape of red? Is there a color that I could show you which you might consider red and someone else would not?

The core problem is this idea that 'explanations' in the source are implicitly able to be fully specified or that any knowledge exists without practice. See i.e. W's theory of language for a mind blowing explanation.

I think the real question I would pose to the author is, what knowledge do you think qualifies as 'explicit'? I think you will find your answers supremely unsatisfying. If you don't, try Kripke's 'Wittgenstein's Paradox' and Goldfarb's (admittedly much more dense) 'Rule Following'

> Tacit knowledge is knowledge that cannot be captured through words alone.

This definition is slightly wrong. Tacit knowledge can't be described in words alone, but it can be captured through words alone.

One of the reasons we built FWD:Everyone (https://www.fwdeveryone.com) was to capture the tacit knowledge contained within email conversations. When you can see the entire conversation, you learn how people interact with one another and you can learn to model your own communication based off of that. That knowledge isn't contained in any individual sentence, paragraph, or message, but rather as an emergent property that's only apparent in the context of an entire conversation or many conversations.

There is a ton of value in this that can never be captured in a wiki, for example.

> you learn how people interact with one another and you can learn to model your own communication based off of that.

This strikes me a little like "By reading lots of good code, you can learn to model your own code based on that". It probably helps, but a lot is dependent on context.

The blog post goes into this with the long quote about choosing tools and techniques for an appendectomy. How do you capture that sort of context in an email thread? Annotations like "Based on X and Y factors, I chose to write Z", where X and Y are not explicit in the email text?

I haven't looked too closely, but it seems to me that the primary value of these email threads (in terms of learning communication) is to provide a body of real-world examples - but there also needs to be applied experience (with feedback) with written communication for the lessons to really sink in.

> The blog post goes into this with the long quote about choosing tools and techniques for an appendectomy. How do you capture that sort of context in an email thread?

I mean in terms of our tool, the knowledge is either already in an email or it isn't. It's meant for retaining knowledge that's already being created anyway. You certainly could purposely capture knowledge in email for the purpose of being viewable and searchable in our tool (and some people do), but in that case there may be other better tools.

Been waiting ages for literally anything posted on commoncog.com to get traction on HN, because it's all interesting deep writing about meta-human issues, useful for "us lot" and invokes good discussion.

When I see a new post from commoncog, I don't read it right away. I think "right need to carve out half hour of quiet uniterrupted time for that later".

It's one of the few I have on my mobile phone RSS reader, the others being quanta magazine, and another interesting blog I found through HN.

So that's my praise, I recommend you add it to your readers too :-)

We have neural networks in our brains which for some reason cannot be trained without practice in real world. No amount of reading about riding will train those real-time feedback loops that operate on much lower latencies then you can formulate conscious thoughts.

This is a limitation of our brains and not fundamental property of knowledge or information.

In AI neural networks which can ride bikes or recognize objects are easily introspected and copied. In humans this isn't implemented ;)

Isn't what we call thinking simply an introspection layer on top of our neural network hardware? Sometimes I wonder whether the entirety of what we call the mind is just an epiphenomenon that attempts to explain the workings of our neural network after the fact.

If that were true, then cognitive behavior therapy and meditation would have no effect. It's more likely a feedback loop between introspection and the neural network. Sometimes you need the slow, deliberate planning that comes with conscious thought.

But what if the urge to seek CBT is itself a part of our ex-post-facto narration?

I believe this is how you learn:

* I watch you do it. * You watch me do it. * Then I do it.

I have to watch someone else undertake a task to understand it. After, I attempt to undertake the task and receive feedback from the individual whom I watched first. Then after I've gathered the knowledge I can do the task. The context I learned about this approach was when I learned to use a chainsaw. But it has served me extremely well in both learning and teaching other topics over the years.

Does anyone know of a service or website that matches mentors with apprentices?

I know there is https://www.apprenticeship.gov/ but I am thinking something more informal and online, e.g. a marketplace where you can match and pay $X/30 min. of quick and focused Q&A.


I've used it a couple times to get help with roadblocks and such..

Getting a second pair of eyes on your code is nice!

>> The process of learning tacit knowledge looks something like the following: you find a master, you work under them for a few years, and you learn the ropes through emulation, feedback, and osmosis — not through deliberate practice.

I feel fortunate to have stumbled into an organization where this was the case as a junior engineer. The company wasn't ever wildly successful, but I feel lucky to have worked with very smart people when I was very green, and couldn't make heads or tails anything.

Patience was certainly needed on their part I'm sure, and such frustration is likely what leads people to become pedagogical at times.

As a bit of a thought experiment; would Simulation be the closest we have towards "Transmissionism"? I'm not arguing that it is or isn't, but whether we can approach those non-verbal and tacit knowledge as encoded through programs and data?

To throw out an easy counter-argument, we could say that Simulation/Programming is like comparing Words to an Image, aka nothing of the sort. Additionally, there is the difference between Simulation and Reality, where simulation simplifies or glosses over many elements of reality. Looking up the definition indicates that Passivity seems to be the key, and simulations are anything but passive.

To give a concrete example of what I mean, in my early career I worked at a defense contractor building a training simulator for a weapons platform. The training was to mimic the same training on a gun range. Soldiers were graded by the simulation as if it were the instructor with a sharp eye and a stopwatch. It tested everything from how long you held the trigger (at least three seconds), how you swiveled your head to scan for targets, identifying targets and relaying them to your vehicle commander, etc.

I would argue that it goes beyond Transmissionism, as it now corresponds far more to an actual reality than mere metaphors and words. However it does make me wonder where the line might be, if it even exists.

In high school physics class there was one kid that seemed to be really good so one day I asked him what his trick was and he said, "I just pretend I'm the teacher". I thought that was a really clever trick. During class he was figuring out ways of how to copy the teacher and it seemed to work. He would consistently get top marks on tests. He was accumulating tacit knowledge whereas everyone else was copying formulas and drilling problem sets.

I wrote my master's degree on innovation management. Tacit knowledge was termed by Michael Polyani and Nonaka and exploded this sub genre of knowledge management and innovation management. I recommend reading their seminal papers.

But it's all down to the type of knowledge involved in skills you have acquired such as biking or walking, and things where you can extoll an intuition versus explicit knowledge such as a pizza baking recipe.

This is actually how knowledge was transmitted traditionally. As an apprentice/student you just copied the master who would steer/nudge you in the right direction occasionally. Otherwise you just did the activities blindly until slowly you self-regulated and moved onto deliberate practice stage. This can be most clearly seen in the study of martial arts. Musashi called it Heiho/Hyoho in his A book of five rings.

I believe the key here is to focus learning on the overall activity (i.e. systems view) rather than the constituent individual pieces. Focusing on the latter just overwhelms you with too much detail leading to doubt and confusion. For example, in Software Development, if you try to focus on every single aspect like Correctness, Error handling, Generalization, Optimization etc. in the beginning you simply will never get anything done. Instead focus on just getting "a program" done using whatever knowledge you have. Once that is ready, then modify it deliberately for meeting all your other criteria.

This is why language/framework design is so interesting. After enough time spent with one a developer will be running off tacit knowledge.

Extending/patching that doesn’t fit in with tacit knowledge is also dangerous. React has done a great job of that, it looks much different than a few years ago, but the changed behaviors never felt “wrong” internally.

When I finally learned how to ride a bike, I was annoyed that nobody had told me "to keep the bike balanced, if you start to fall to one side, turn the steering wheel in that direction".


It's a good exercise to frequently try to verbalize your tacit knowledge. The alternative is to constantly be appealing to your own authority.

Lots of people have faulty tacit knowledge.

Michael Polanyi's "The Tacit Dimension" is a good starting point on the concept.

Tacit knowledge sounds like an untestable phenomenon, and simply lacking the words to describe certain neuromotor techniques doesn't mean that it cannot be communicated explicitly in theory. Perhaps in the future we'll have a way to stimulate the brain in exactly the right way in order to communicate how to keep your balance on (aka "ride") a bike.

Furthermore, articles that downplay the importance of practice, to me, seem like a bad idea. In my experience, people who claim a high level of general comprehension (but not technical) tend to lack the ability to implement any facet of their "tacit knowledge" at even a basic level.

Dear bloggers. I hate it when you spend several paragraphs explaining your personal reasons for wanting to write about a topic, particularly when those reasons have nothing to do with the topic at hand.

Don't talk about it, be about it.

I hate it when you spend several paragraphs explaining your personal reasons for wanting to write about a topic

Literally the point of a blog. That's why it's their blog.

A long time ago in a philosophy of math class, our professor offered this problem: upon hatching chicks have to be separated by sex. Experienced poultry farmers know how to tell them apart from feel but it's not a process they can describe. The problem then was: how would they teach it to a new hire? The solution offered was that they have the rookie hold the chick in their hands and guess while the experienced farmer corrects them. This was a great example of how tacit knowledge is acquired.

And explicit knowledge (that you can explain to others) is more important than tacit knowledge, if you're trying to coach or teach someone

Isiah Thomas was one of the best of all time, but was a disaster as a coach https://www.sbnation.com/2015/5/5/8553115/isiah-thomas-new-y...

I don't think "knowledge that can't be put into words" is a good final definition of the skills that allow people to achieve excellence. It's an OK "first order approximation" but when it implies "nothing you can say will be useful", it seems more like a hindrance than an insight.

I've studied martial arts and body work. Naturally, many of the skills involved are taught hands-on rather than through a verbally specified sequence of actions. And it's definitely true that balance or an effective stance can't be taught by just sequences of positive commands ("stand straight, chin out" or whatever). However, high level (or more effective) skills can be taught through a combination of hands-on direction and verbal direction telling the student to "explore", to "relax", to "be aware" - these verbal direction represent internal, non-verbal processes ("balance centers", etc) and tells the student to yield to these. That yielding lets these processes get the skill and knowing how to so yield lets the skill be available. It's not avoidable verbal but it's not a simple rationalistic recipe.

I don't think so. People only listen to people they admire, they don't listen to people they do not.

If nobody listens and respect you you can't be a good coach. This happened in Real Madrid with a coach that had been a mediocre player. The "top of the world starts" did not listen to this person because they did not admire or respected him.

In Rocky the film for example you see as Rocky gives an advice to a kid, before he is famous. The kid does not listen because "Who are you? A loser".

This could happen even if the person is a master, because of envy. I remember a man that was very successful with women, and wanting honestly to help others do the same, only to being rejected by others because they felt threatened or envied him so much.

I see this every day, when someone who is successful at something because he does something better than others. But others do not admit that this person is better creating rationalizations like "this person is so lucky", and then they will generalize even further "all success is luck", when they could not get it.

I know because I have learned a lot from those people and in some ways replicated their success. The only thing I needed to do was admiring that they were better than me at something, being humble at first, and that looks easy but it is very hard because it goes against your ego.

I took a skiing lesson from a master and he looked at me skiing and made me practice basic sky lessons: the kind novices take.

I remember thinking: WTF! I already know how to ski well!! But I forced myself into listening and doing exactly what he told me, even when it looked ridiculous and made no sense.

My skiing improved radically because of that.

"When I pushed these people on their judgments, they would try to explain in terms of principles or heuristics. But the more I pushed, the more exceptions and caveats and potential gotchas I unearthed."

It is a popular believe that being an expert on something doesn't mean you will be an expert on teaching that thing, but in this case it could also be that any number of implementations was possible, and the seniors had more clout or were more pushy.

I think of it the other way around: Until I can teach the thing to someone else, I am not yet an expert.

It seems as if I've been using a different definition of deliberate practice to the author. They seem to imply that deliberate practice requires a regimented study program, but I've always seen it as "identify the things you are weak at and drill those things, rather than repeating tasks you are already comfortable with". Is there a name for the type of practice I've been doing?

Yes, K. Anders Ericsson (he of deliberate practice fame) calls it 'purposeful practice'.

I believe deliberate practice can work in the same direction if the practitioner is aware of the fact that there will be huge gaps in the knowledge acquired through practice.

I like the idea of discarding the results of exploratory processes that GeePaw Hill elaborates very well. It removes the incentive of trying to reuse artifacts that were created "while learning" and just bring back the lessons learned.

Most of my software design is "wordless." Part of it is because I have a brain that is wired a bit "funny." I'm sort of "on the spectrum," and get into a "fugue" when I code.

In fact, after coming out of the "fugue," I can have trouble with verbal articulation.

But when I am in the "fugue," I can actually design a pretty intense system, without writing down a thing.

One very helpful thing to understand wrt this idea of "tacit knowledge" especially in terms of understanding and managing personal relationships...

You or someone you know may very well become aware of (i.e., _come to know_) what are your personal defects (insecurities, unproductive behavioral predispositions, etc) -- but this is in no way _at all_ means that you will be able to _change_.

The John Boyd example is super interesting. My understanding is that he essentially built a framework for thinking about dogfighting, the OODA loop. Very similar to how the author put kids on tiny bicycles. You can't tell someone what to think, but you can _design a system_ that makes it so that they think about the right thing at the right time.

This is how we "teleport" thought from one person to another, we have to replay the same series of events that enable them to have the same thought patterns. Communicating and educating is basically replaying the stage for the same thoughts to form.

“For the things we have to learn before we can do them, we learn by doing them.”

― Aristotle, The Nicomachean Ethics


This is why every attempt to "systematize all human knowledge" cannot succeed.

Tacit knowledge concept connects a lot of dots. It was a missing piece of the puzzle.

Really interesting article.

Amazing post! I didn't know such type of knowledge existed. Eager to learn more.

See https://www.youtube.com/user/troygrady . Troy Grady is an extremely successful externaliser of tacit knowledge.

I kinda think he's talking about intuition. It's the non-verbal understanding that underpins mastery in any domain. If deliberate practice is the means, then tacit knowledge is the end.

> “Because we want to use it as a database layer. Quite risky ah.”

Singapore represent!

I'm agreeing with the idea of the article, but I believe that Tacit knowledge which can't be attained with practice would call Talent or In-born gifts. For example, no matter how much chess I'll play and deliberately practice for 20 years I can't beat Fischer, Kasparov, Karpov etc.. since they are talented (Tacit knowledge) that doesn't mean they can't open their talent through books like "Bobby Fischer teaches Chess" or books about chess by Karpov (but who would do that during matches of chess). Deliberate Practice is the best way and most fast method for acquiring a skill

Deliberate Practice leads to Tacit Knowledge.

Or rather the former trains the acquisition of the latter.

Is having a mentor necessary ? Can't it be gained in other ways ?

Deliberate practice builds tacit knowledge. Uninformative article.

Immersion builds tacit knowledge. Deliberate practice may or may not require immersion.

I can see that. I just don't (didn't?) see deliberate practice as not immersed. Fair point.

Tacit knowledge is the result of deliberate practice.

Isn’t there already a long philosophical analysis of this phenomenon — know-how vs know-what?

In general, I agree with the notion that tacit knowledge is often more important than explicit knowledge - and that it may actually be the very essence of human expertise. However, it seems the author mixes some things up.

First of all, deliberate practice rests to a high degree on a) pre-existing knowledge on the structure of acquiring a skill and b) an established feedback standard that allows to evaluate your performance. These are obviously crucial aspects. If you don't know what characterizes expertise and if you don't know why you're not doing well - then it's difficult to make actual measurable progress. That said, it doesn't mean you can't become an expert at all in a field that does not have those elements currently available. It may just be that you need to put more effort into doing it, seek a mentor known for relevant skills or develop feedback mechanisms to evaluate your performance [1].

Thus, I don't think the distinction made between tacit knowledge and deliberate practice is really helpful. From my understanding, the concepts of "tacit knowledge" and of "deliberative practice" operate on two different levels. Tacit knowledge (or originally tacit knowing) refers to the implicit character of some knowledge. Its counterpart is explicit aka codified knowledge. Conflating deliberative practice with (the acquisition of) explicit knowledge seems counterproductive to me. It seems to me that the author wants to argue that deliberative practice only contributes to explicit knowledge.

I get that explicit knowledge may be needed to create learning environments (and gained before through codification of tacit knowledge) that respond well to the principles of deliberate practice. From my reading of Ericsson that does not mean, however, that deliberate practice only works to build up codified knowledge. Tacit knowledge is in itself a vague concept that is hard to grasp. I wouldn't be confident to assert that building up tacit knowledge happens without building up codified knowledge. Maybe someone knows more about that?

Another aspect of the article that concerns me represents the part about the acquisition of knowledge and expert systems. There seems to be another conflation of concepts. It is referred to Klein who (in reference to humans) warns about the overreliance on fixed procedures for decision-making. I agree with that but nevertheless I'm having a hard time with the argument in the article's context. For me this seems to be more of an argument about having a human making a decision than about the superiority of tacit knowledge over deliberative practice or even codified knowledge applied by a human. I get it, humans can build up tacit knowledge and therefore have an advantage over expert systems in previously unknown situations ... I just don't get the relevance for human acquisition of knowledge here which the article wants to be about.

A similar issue I have with the argument about the scope of deliberative practice and NDM as better alternative. Now I have to say I heard about the term NDM for the first time today (and I'm glad I got introduced, thanks!) but from what's written down in the article, it doesn't really seem to be in conflict with - or even that much qualitatively different compared to - deliberative practice: "you find a master, you work under them for a few years, and you learn the ropes through emulation, feedback, and osmosis". This seems to be possible under the concept of deliberate practice as well.

To get a better understanding, I've read another article from the same author [2] but I'm a bit confused. In the end, NDM just seems to offer more concrete procedures to acquire effective and adaptable mental models (in terms of deliberative practice) that help you to make better decisions. But that can't be the catch of NDM, is it?

[1] I'm currently reading Ericsson's book "Peak" and he mentions the Top Gun academy of the US Air Force as an example for the possibility to develop a "deliberative practice"-like environment.The program was designed to enhance figher pilots' performance by having those pilots surviving the initial air fights in Vietnam to become teachers to new pilots. Establishment of good practices took place through the constant exposure of the teachers to new recruits and constant training on usual fight situations.

[2] https://commoncog.com/blog/putting-mental-models-to-practice...

This might help clarify my problems with deliberate practice somewhat: https://commoncog.com/blog/the-problems-with-deliberate-prac...

First of all, thanks for your post! It was an interesting read and I've subscribed to get updates.

Yeah, that was really helpful. I think the argument you make about 'fractionated pools of expertise' is actually the most important. I'm still a bit confused about the differences between "practice" and "decision-making" and their relationship to knowledge (either codified or tacit) but I guess that will now be part of my list of things I want to learn more about.

Haha, I see I messed up a bit. It should be "deliberate practice", not "deliberative practice".

Blog posts are like youtube videos, you have to skip the first 30% to see the "actual" start.

>[...] every time I touch on the topic of tacit knowledge, inevitably someone will pop up on Twitter or Hacker News or Reddit or email and protest that [...]

One of these is not like the others.

Tacit knowledge is the lowest rung of understanding. It's the understanding that cats and dogs form, unable to talk but able to listen and consider. The main difficulty is that, because one cannot express tacit knowledge, one cannot reform or improve it.

Part of why operationalization is so important in the hard sciences is because it gives us access to otherwise-inacessible things, including tacit knowledge. The only knowledge that is tacit for the typical person is the knowledge of how to move muscles. For example, to whistle, the tacit portion is the pursing of the lips, but the rest of it is music theory which can be communicated and taught using language.

> only knowledge that is tacit for the typical person is the knowledge of how to move muscles.

Thats's not really true.

If you are a native English speaker, it might surprise you to learn that English adjectives have a default order. We normally say "the big red ball" but "the red big ball" sounds decidedly odd unless there's an explicit contrast ("No, not the blue one. I want the red big ball"). This is apparently taught in ESL classes, but neither I nor any of my native-speaker colleagues remember learning it in school.

You have an "intuitive" model of physics in your head that allows you to rapidly determine if piles of objects are stable without grinding through balance-of-forces calculations. It's not exact, and deviates from reality in interesting ways, but it's there. https://www.pnas.org/content/110/45/18327.short

You have all kinds of implicit priors that help you make sense of sensory input. You have some idea of the speed and smoothness with which things move, how an object's apparent size changes as you move towards or away from it and how it might look under different lighting conditions. People share some, but not all of these priors, and they're hard to elicit, hence the endless discussion about The Dress that was either black/blue or white/gold.

Exactly. There is a rule but I would venture that very few native English speakers know it or were taught it; it's learned implicitly instead. I only found out there was a rule because I stumbled across the phenomenon doing a computational linguistics project.

My broader point (which I made poorly) is that native levels of language proficiency require a mix of explicit and implicit learning. There are certainly explicit rules for verb conjugation and agreement. Some things can be learned either way, like adjective order. Others seem to be mostly implicit: I can't give you a general rule for why "I asked her to marry me and she agreed" sounds fine but *"I asked her to marry me and she concurred" sounds weird.

This knowledge that you are discussing is quite interesting, but not tacit: You had no problem explaining it to me in words alone. Moreover, it can all be operationalized; physics in particular is well-operationalized and usually evaluated numerically.

I gather that part of the tacit-knowledge movement is to talk about knowledge that cannot be put into words. The example of how to move a muscle is extremely instructive: There is no sequence of words that will allow a person to examine and select the correct bundles of nerves for moving a muscle, and instead a person simply must learn to do it somehow. Even then, if somebody does something like isolating grouped muscle movements, they might be able to explain in words how to fine-tune control over some muscles.

The adjective case might be debatable, since it's usually learned implicitly but could be taught.

Intuitive physics may be a stronger example: the point is that it's not "real" physics where you numerically evaluate the statics and centers of mass. It's a set of heuristics that let you rapidly (and not always successfully) determine if a pile of books is stable, using some internal model of the world.

Ditto for sensory input. You have all these built-in principles (or priors or biases) that have evolved over millions of years to help you make sense of ambiguous or impoverished sensory input. These are also mostly implicit.

We can certainly name these effects talk /about/ them, and even probe them with careful experiments....but we can do that to bike-riding too.

I have multiple ABET-accredited degrees in engineering.

I learned more about how metal works in 2 months in a machine shop than i did in 4 years of undergrad and 5 years of grad school.

"Knowing that" is nice, but it is not the same as "Knowing how", and one cannot beget the other.

This is interesting.. I've never heard of the term "tacit knowledge" before, but it makes a lot of sense to me. It particularly reminds me of my experience being on-call at my last company.

Our systems were pretty unstable, and the most stressful part of the job was getting paged at 4am when everything was falling apart, customers couldn't use the app, multiple analysts would be sending messages asking "what's going on?", and as the on-call engineer, I happened to be the last line of defense (the system wasn't managed by a devops team).

In that moment, there's a lot of stuff that has to be done quickly: - orient yourself and figurate out what's going on (even in a sleep-deprived state) - prioritize mitigation over root-cause analysis - communicate early and often with the stakeholders present

This isn't stuff one can pickup by reading a "runbook". It took years of working with the systems, absorbing knowledge from my senior co-workers, and learning from past mistakes to get to a point where these priorities became in-grained in the way I approach outages.

So from my own experience, I would disagree with the definition that tacit knowledge is purely muscle memory or that it can't be improved. One's mindset can certainly evolve and I would consider that as "gaining" tacit knowledge.

I would even say something like music theory can be tacit knowledge. If you talk with musicians that do a lot of improvisation, they can certainly talk to you about music theory, but they're rarely "thinking" about music theory when they play. Just intellectually telling someone how notes/chords relate to one another doesn't transmit that "feeling" one needs to create great music.

Science is what we understand well enough to explain to a computer. Art is everything else we do.

-- Donald Knuth

By this definition, chess used to be an art, but is now the domain of science.

“Tacit knowledge can be defined as skills, ideas and experiences that people have but are not codified and may not necessarily be easily expressed”. By that operational definition, “muscle memory only” seems to be a rather overly constrained attribution of knowledge to the typical person.

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