Hacker News new | past | comments | ask | show | jobs | submit login
Four Hours of Concentration (johndcook.com)
334 points by wmat on Feb 5, 2013 | hide | past | favorite | 86 comments

Unbelievable, 40+ comments and not one contrary opinion.

Alright, I'll be that guy. I have no trouble doing more than 4 hours worth of mentally strenuous work in a day, and neither do most of the people I work with. Frequently enough I've put in sustained 12-16 hour days for weeks on end to meet a tough deadline.

You'll generally find that the most successful people who are best at what they do have no trouble with this either. I'll go further and say that a large number of the people who complain about having to work more than a few hours a day are doing nothing more than rationalizing their lazy HN and/or reddit habits.

I think you define "strenuous" quite weakly. The overwhelming majority of jobs don't require very much cognitive effort, even in software. Most developers hardly ever actually do anything legitimately hard in their day-to-day work.

Proving theorems is a completely different class of work to chipping away at your failed unit tests or knocking together a CRUD app in your favourite language. Maybe a tenth of one percent of software developers routinely do work that is intellectually on a par with mathematical research; The rest are for the most part skilled tradesmen, doing work they understand relatively well.

It is universally accepted that all but the most prodigious musicians do not benefit from more than 4 or 5 hours of practice a day. They can often easily do twelve or sixteen hours a day, but the extra time is simply wasted. Once your reserves of concentration are spent, you're just going through the motions without learning anything. Most conservatories go to great lengths to persuade their students to practice less, because young musicians are often convinced that they can attain mastery through sheer force of effort.

I can sit and transcribe or arrange parts all day long. I can play from sheet music until my hands give out, all the while daydreaming about what I'm having for tea or what chores need doing. I can't usefully improvise or compose for more than about two hours at a time, or more than four hours in a day. I can feel the point at which I start playing familiar riffs rather than truly improvising; When I've run out of ideas and I'm just writing pastiche. There are composers who claim to do regular eight-hour days, but when you look deeper they invariably spend most of that day arranging or transcribing or recording into the computer, stuff that's essentially just admin.

>Most developers hardly ever actually do anything legitimately hard in their day-to-day work.

I might agree with that in an absolute sense. But if we're going to talk about percentiles, and relative to the human population, very few people (percentage-wise) can even do the "easy, boring" part of programming you're referring to.

It is hard to learn. But once you learn it, not that hard to do CRUD day to day. When you have to learn some new framework/library it gets harder again.

Well, as a mathematician, I can say the same is true of mathematical research. Climbing Mount Bourbaki is a difficult endeavour, but from the top the pastures are relatively peaceful to explore. Most papers are not groundbreaking theoretical sledgehammers, but minor updates on footnotes of a vaster theory.

This matches my experience about technical, "it's complicated" knowledge in general: the hard part is catching up to what everyone knows, but once there, contributing and improving are surprisingly easy and obvious.

Just recently I was given a task of debugging a major problem with our website that was causing frequent emergencies -- and apparently, was mystifying the developers.

My lead realized I'd need to understand the website's infrastructure first, so he took about 45 minutes explaining how it all fit together and where the problem occurred. But once I got to that point, my reaction was, "Wait -- wouldn't the problem go away if you just ... didn't do $STEP at that point?"

Turned out to be the entire solution to the problem.

Hey, I'm not the one you need to convince. You should be talking to VCs about your great idea to save money on programming by hiring burger flippers and turning them into mediocre programmers.

Perhaps you missed the part where he said it was hard to learn.

I'd be shocked if those 12-16 hours you apparently put in for "weeks on end" are truly your most productive. They may certainly feel "mentally strenuous," but that doesn't mean your cognitive limit isn't decreasing as the days and weeks go on.

I find that I can focus intensely for shorter bursts over a couple hours, but then I hit my limit and need to push the really hard stuff aside for a while. Sure, I can crank through a ton of tedious or menial tasks (and there are certainly plenty of them), but that's really not the same.

When I complain about being expected to sit around for 8, 9, 10 hours a day (and I do occasionally complain), it's not because I'm rationalizing lazy habits or want to get out of work. I love my work.

No -- It's because in only 3-4 of those hours I will finish 90% of what I ultimately get done in a day. The trick is in knowing how to optimize those hours of productivity, and when to go home and give your brain time to decompress.

I believe you were sitting at your desk pressing keys for sixteen hours a day. I also believe you believe you were accomplishing more than you would have at your desk for six hours a day.

It's been shown what actually happens in such a scenario is that your judgment quickly becomes impaired to the point where you are no longer capable of judging how impaired you are; it's the equivalent of being permanently drunk. To be sure, you can still press keys. If the work you're given is far enough below your peak ability, you may even eventually blunder your way into a solution. (Or you may not; last I checked, the failure rate of software projects is still several tens of percent, and stupid hours feature prominently in most of the failures.) But the calendar time to get your job done is longer, not shorter, than it would have been with an intelligent schedule. Degrading yourself like that is nothing to be proud of, and it does nothing but harm to your work as well as yourself.

Absolutely. When I've seen things like this in person, the reality is often, "I worked 16 hour days for 2 months coding, and then spent another 2 months in QA fixing bugs."

People say that like I'm supposed to be impressed, but they don't seem to realize that programmers can be negatively productive. In 10 minutes of stupid, I can put in a bug that soaks up a day of somebody's time later on. But the people proud of their death marches act as if the bugs are all caused by cosmic rays, not their own previous exhausted fumblings, miscommunications, typos, and oversights.

If I were to hire someone, and he claimed he can put in 12-16 hour days for weeks on end, I'd be inclined not to hire, based on the expectation that it means that he's either bullshitting me, or does not understand his own limits.

In 17 years of managing many dozen staff, mostly developers admittedly, in a variety of different settings, I've never seen a someone that managed to be productive with mentally strenuous even a full 8 hour day at a time other than very occasionally when they're on a roll. Generally, the ones that do best are those who manage to spread out their work, take proper breaks and intersperse the rest of their mentally demanding work with "menial" tasks, and who goes home and puts their work away completely.

Maybe your're an exception, but if you are, be prepared that people will either disbelieve you or expect you to prove it. More likely, your idea of "sustained 12-16 hour days" only actually involves a few hours of what the rest of us would consider mentally strenuous work a day.

Put in 12-16 hour days for a while with repetitive, simple tasks taking most of the time when working on something that is overall exciting, sure, that works for a while (though eventually that too tends to produce burnout - I've had to order developers home after the strain starter producing negative results with fewer hours than that).

For me, what works best is that whenever I feel that my concentration is slipping, if I don't feel I have time for a proper break, I will switch to mindless tasks, such as updating my todo list (often spending time breaking bigger tasks into tasks that are realistically small enough for windows of a couple of hours), doing my e-mail, or if I'm home I'll do the housework, and I'll try to "switch off" while I do, practicing mindfulness meditation for the truly "mindless" tasks such as cleaning.

Sometimes I get lucky, and my concentration stays on top for longer in one go, and I cherish those moments, but I "pay" afterwards (e.g. crash on the sofa when I get home, or need to slow down the following day).

I think the only thing we might say with confidence is that physically fit and keen-to-impress types are able to sit in their chair for 12-16 hour stretches.

I'm sure you're working hard on demanding things, but a world-class violinist is probably doing something much, much harder than you are. Even if you don't respect violinists, surely you have to respect that an expert mathematician trying to make a new discovery is working on problems much harder than anyone in the corporate world. So I don't think this article applies to you, or other people working long hours either, or to people who should be working long hours.

What is a typical day for you? You are a founder so I assume your day is broken up into many different roles. This is very different from a programmer or writer who is focused on doing basically one thing for his whole work day. Do you have any health issues?

> Frequently enough I've put in sustained 12-16 hour days for weeks on end to meet a tough deadline

I think many of us have done this here. What I've noticed from doing this is I start to make lots of mistakes that I wouldn't normally. At a certain point, this turns into a vicious cycle where I think slower and make more mistakes so I need to work more to fix them.

Maybe you're superman and can really work all those extra hours at full concentration...but probably not.

Here's an easy way you can check. Use a timer and throughout the day start the timer when you are going into work that requires full concentration and then stop it when you're done or someone interrupts you or you need to go to the bathroom or you break off from your task. Meetings and emails don't count.

I think you'll be surprised at the results.

I think you may be missing most interesting point of article which is about the cognitive limits of enhancing skill through deliberate practice.

There was an academic paper a few years back "The role of deliberate practice in the acquisition of expert performance" ( a nice summary here - http://blog.vivekhaldar.com/post/3881908748/tldr-summary-the...). The paper breaks down 3 types of activity: work, play and deliberate practice. Work is exercising skills you already know; Play is creativity, fun, exploration; Deliberate practice is building a skill - where expertise is achieved through focused training in a particular skill. The article suggests there is evidence that it takes about 10yrs to acheive expert status in a skill. Malcom Gladwell introduced a similar topic through pop-sci writing "Outliers" - suggesting there was evidence that becoming an expert required 10k hrs of practice.

To me, practice requires the absolute most concentration - unlike 'work', with 'deliberate practice', by definition, you can't supplement skill with experience for efficiency.. to learn you have to evolve skill from more experiences. And I believe thats why the linked articuled a 'cognitive limit' of 4 hours by way of a violinist practicing in spurts of 2x2hrs=4hrs per day.

The last paragraph in the article talks about "four hours of intense concentration per day", and I'm not sure I buy that abstraction because "concentrating" and "training" are 2 different things. The author (and interviewee) is inferring that concentration is the constraint, but I'd suggest its more likely learning/trainability speed constraint.

So, a different interpretation, but I may be agreeing with you own observations. I think deliberate practice shows an upper bound for cognitive limit - but in the sense of new patterns being formed in the brain. I don't think deliberate practice necessarily shows the upper bound for concentration based on the information presented.

Absolutely right on the money, very well put. To me, mental practice (where you are really growing) feels just like going to the gym. You work out, and your body becomes exhausted. At that point, its counter productive to continue to work out. You rest for a while, and you come back stronger.

Anecdotal example: I used to work for a small company where the programmers did both algorithmic design and the implementation. Looking back on that work, I could write code to sling bits from point A to point B all day (and did the 12-16 hour weeks you mentioned for months on end). But there is no way in hell I could do algorithm design for 12+ hours a day for weeks on end. It's extremely dense work. There's no mental breaks while waiting for the linker to run, or long stretches of babysitting the program in the debugger, or breaks of mechanically typing out something you've already thought of. It's just you and a pad of paper, thinking the whole time.

The article refers to mathematical work, which is by its nature very dense, much more dense than other intellectually-demanding jobs like programming. As a programmer, you might spend half an hour now and then thinking through all the potential race conditions in a parallel algorithm. But you don't do it non-stop all day, day in and day out. Most of your time is spent on things that require far less concentration.

Thanks for being "that guy." I think that your day probably has one or two peaks in it where you do your best work, and the rest is more low energy work (not bad, just not the most effective work on tough stuff.) Also, not all hard workers are created equally, so among those who do hard work, some can do more than others. I agree they become more successful but I do not agree their working habits can always be duplicated.

I certainly agree it is tempting to read about four hours of concentration and use the article to justify four hours of mediocre work.

I have happily programmed for long stretches - refactoring, doing project work, mentoring others. Once you've been a developer a while, you can produce magic without very much mental strain.

Break away from that and do something truly difficult - specification meetings where you're designing a process for huge pieces of hardware that haven't yet been built - studying something complicated and unfamiliar to you - etc - and perhaps you'll find - like me - that you've only got a few hours available to you before your brain turns to mush.

It might be correct about the 4 hours. It might also be irrelevant for most people. For most disciplines, accomplishing anything consists of some cognitively very demanding work, and a lot of 'admin'. Some violin players and mathematicians may get by on doing only the hard stuff, but most have to apply for grants, participate in conferences, transcribe/arrange, maintain equipment, etc.

For a startup founder I think this is especially true. A lot of the things you do won't be very cognitively demanding. That doesn't mean you can skip it if you want to get anywhere. It doesn't even mean those 'menial' task create less value in your context than the hardcore 100% concentration parts.

Maybe when you've settled down to a predictable working pattern and managed to configure your environment to cater to all the necessary but trivial tasks (and create enough value in your 4 hours to pay for other people taking care of the rest) you can realize this. I'm not there yet.

How many of you are over 25 years old?


It seemed to me that the research cited was likely a bit thin. I couldn't tune a guitar, so I have no idea about violin players. But there have been notable cases of very hard-working creative types--Flaubert and Sand come to mind, and Herbert Simon (Turing Award, Nobelist in economics) claimed that a 60-hour work week was about right for him.

I don't intentionally try to structure when/where/how I think about things, but after 23 years, I've gotten pretty in tune with knowing how things 'feel' inside.

I know if I'm going to have a shitty day or a great day the moment I wake up, the first interaction I have with a person (knowing this may make it more likely to happen, but short of that...).

I know when my brain is running on all cylinders, and when it's choking for more air. Tuning into these signals (I have no idea what they are, only 'feelings'), I can lay out the things I want to do in the next few days, and roll with the punches. It'd be interesting to see the amount of time idlers and time progressors (I'm at my computer most of the day, looking at my google search history would give a good indication - I generally don't google that much when I read articles on HN or Reddit, but when I'm doing something I'm googling up a storm).

No sense fitting a square key into a round hole when tomorrow the round key will be sitting in my hand.

You have to be careful not to give too much weight to something that can have self fulfilling prophecy effects- i.e. "I'm going to have a shitty day" sets you up to have a shitty day. I'm not saying its bad to listen to your internal compass, but you have to make sure that you aren't just giving yourself excuses. In my experience, I found that sometimes I have done exactly that, like I have something difficult to do and all of a sudden "my mind is tired, now isn't a good time."

In my experience this is what happens with programmers in corporate environments and produces excessive hours - 2 hours concentrating in the morning, 2 hours concentrating in the evening, and 8 hours of bullshit in between.

Wow, 2 hours of concentrated work in the morning sounds exceptional to me. With open plan offices -- the norm in Brazil and Japan -- it's damn near impossible to have 20 straight minutes of uninterrupted work: phones ringing, people talking to each other from afar, people interrupting you, etc.

Incidentally, would the 2 hours of concentration take place at home? See: http://dilbert.com/strips/comic/1995-09-15/?CmtOrder=Rating&...

No joke. Sometime the only time I get un-interrupted stretch of 2-3 hours is at home, at night.

Same for me, once my wife and kid are asleep

I'm a proponent of this theory, and it worked for me in Law School. I would only study for two two hour sessions each day, after which I was free to do whatever I wanted. This worked quite well for me, and I always felt fresh and sharp, especially when finals came around.

I also did the same study plan for the bar exam and feel like it worked well there too, i.e. passed it on the first try with a minimum of drama, the whole thing was actually quite pleasant.

In contrast, many of my peers would study basically around the clock, pull all nighters, made their lives miserable and didn't do any better, and more often than not quite worse.

I tend to agree, although I think you can concentrate longer for short, unsustainable durations. My standard schedule in law school was a few hours during the semester, then a few weeks of 8-10 hour days around finals.

My take away from the experience was that 8 hours of real work is really a lot of work. And distractions are absolute poison: internet, cell phone, etc. Nothing quite like locking yourself in a room with just a book and highlighter--no computer, no cell phone, no people. You add those things to the mix and it can easily take a 16 hour day to get 8 hours of real work done.

Are there any peer-reviewed studies on this? This looks like purely anecdotal evidence. It makes sense on the surface, but I don't think I can trust that four hours of intense concentration per day is some sort of "cognitive limit" without an actual scientific study.

I don't know about writers and the morning, but there is plenty of evidence that the ideal block of learning or studying is pretty small. For example, you have spaced repetition ( http://www.gwern.net/Spaced%20repetition ), where a few short minutes of studying spread out over time is vastly more efficient than a few big blocks of studying with no subsequent review sessions. And I believe there's a bunch of research on lectures becoming a waste of time after around 15-20 minutes (IIRC, FAA-sponsored).

There are lots of studies that show this actually


I think another item to add to this is that some days that 4 hour day is going to be your ceiling and anything which creates yet more cognitive exhaustion is going to erode that further. For example, serious stress from having to hit a deadline or being overloaded could bust that 4 hours worth of reserves down to 2 or 3. If you try to force it, you might just end up sitting at your workstation all day idling at brainless tasks such as browsing the internet or half attempting to create some sort of structure out of the mess of the task list your clients have sent you.

It's interesting that we see so many articles posted on hacker news on how to be more productive, beat procrastination and be more motivated when really this article the OP posted explains it all. In most cases you probably don't have a problem with procrastination and motivation, it's simply that you are over-extending yourself. Cut back your commitments and you fix your problem.

I have been freelancing for most of my time as a developer, and I have worked remotely for all of it.

The one actual job I had as a web developer set the work week as 40 hours a week (8 hours a day.) This left me wondering if any developers actually work this long of a day and how they could possibly do it.

When I'm doing client work, I'm ON, all the circuit boards are lit up. I can't keep this going for more than 4 - 6 hours per day. If I work a long day, then the next day I'm drained and I have to pay off that debt.

It actually took me years to really figure this out after a life of being trained to the 40 hour work week (parents, my early work life.) The 40 hour model for work is broken.

If you practice something 4 hours per day, 365 days per year, you'll hit the legendary 10,000 hour mark in about 6 years and 10 months.


Does this mean that each of us has a reservoir of about 4 hours of intense concentration per day? When we perform a less-intense task, like driving or facebooking, are we using those 4 hours at a reduced rate?

This sounds like it could feed into another idea - that each human has a limited number of actions per day. Performing actions costs concentration, and so we pay for each action from our concentration reservoir?

In 'How to Create a Mind', Kurzweil states that Kasparov could simulate 100k board positions in parallel. Which was roughly same working knowledge as, say, Shakespeare with 100k word senses (http://books.google.com/books?id=FCcXiBPurdEC - search for 'board positions' and read next 3 pages).

Further, he suggests that each of the 100k may require 100 pattern recognizers in neo-cortex. That means, the brain needs to configure 10 million patterns in total - these are either newly observed, or new relations formed with existing patterns.

I'm sure its not linear, but if you divide 10M patterns by 10k hours, that means the neocortex needs to add an average of 1 pattern every 3.6s, or 4k patterns per every 4 hours (ie, limit for day). Thats about 400k neurons / day re-purposed for learning through deliberate practice to learn 40 board positions / day in chess.


Continuing the conjecture, what we know about about spaced-repetition and mass-repetition might provide some nice bounds for upper limit on how these neurons can be exposed to learning material over 4-hr period to optimize their use as pattern recognizers.

Could make a nice illustrative simulation to speculatively address your question about limits of concentration / learning reservoir.

I think theoretically less-intense tasks use up your concentration more quickly if you do it intermittently with an intense task. Which I think makes the usual "work 30 minutes, Facebook 5 minutes, repeat" cycle quite devastating to productivity.

I think we overestimate how quickly we can really context switch. It's interesting to look at how people respond to stimulants. People take adderall to "help them focus" but what it really does is magnify what I think is a latent resistance to context switching.

Sounds quite similar to the concept of ego depletion : http://en.m.wikipedia.org/wiki/Ego_depletion

Agree - Daniel Kahneman's Thinking Fast & Slow is a good book that addresses the topic. Understanding how the brain works a bit really helped me to get "in the zone" a lot more often and I have certainly seen gains in focus/concentration (which translates into learning/ability) because of it.

That's what I have always said about law. I can do about 4 hours of legal work a day. Then I am absolutely done. I have no idea how my colleagues can clock in 8 hours.

Yes - there are days I can do more. But there are also days I do less than 4 hours. In the long run I do about 4 hours a day. That's it.

Your colleagues likely work 4 like you, then bill for 8. Scott Adams (maker of Dilbert) once said this is extremely common in the corporate world, and my experience largely agrees. Much of the other 4 hours may be spent in meetings, lunches, relocating, gossiping, or internet browsing. You're largely paid to be on-site and aware for 40 hours a week, not to necessarily produce anything.

One of Adams' books has a story about someone who took 2 simultaneous jobs at one company. He would show up early on one floor, then take an early lunch and head upstairs to his other job, where they thought he was just arriving late. The employer did eventually catch on, but until then he was paid 16 hours of work for 8 hours of his time.

> You're largely paid to be on-site and aware for 40 hours a week, not to necessarily produce anything

This really bugged me early on in my career before I understood this. When I started work I would feel disappointed that I couldn't be productive for 8 hours per day. Then I realised that no one else around me was getting probably more than 3 hours of work done in a day so I set my aim for each day at 4 hours of productivity and used a timer to track my concentration time.

I still feel conflicted by it though. When I was freelancing, I tried doubling my rate with the expectation that I would only work 20 hours per week. I think most people thought I was lazy and wouldn't go for it. Hopefully in the future we'll be able to move away from the idea that a 40+ hour work week is ideal.

This might be another reason to bill by the week instead of by the hour when freelancing.

You have to frame your rate in terms that demonstrate the value you'll be providing.

Eg you could say you'll only be working 20 billable hours per week and suddenly it sounds like they will be getting some of your time for free.

The rest of the time is actually taken up with marketing, administration, training etc.

Don't forget that some clients value face time. Sometimes I wonder if a client is just paying me to be around him...

I did contracting for some short stints when I was younger, and quickly realised that this was it.

I could quote a fixed price for some work, and they'd readily accept my rates. But if I then would try to leave after the amount of time the work actually took me, they'd question whether or not I was actually doing the job properly.

So I quoted even higher on the expectation that 1) I'd have to sit in a chair in their office 8 hours a day and so couldn't do other work elsewhere and needed to be compensated extra for that inconvenience, 2) I'd be bored out of my mind trying to fill the rest of the time I was there.

Never a question raised.

It was frustrating. Especially one job where I as stuck for 3 weeks on a machine with no internet connection doing a job I could easily finish with 2 hours every day. Whenever possible I'd work remotely.

Do we have any idea what it actually _is_ what is getting depleted when we start to run out of energy or concentration? It's something I've wondered about already a few times - I mean I can pretty much feel running out of steam myself. Which means there is some way in which my mind is able to measure whatever it is that it causing this.


By and large I agree with this, but I think there is another element to consider, which is your overall energy levels. If you exercise, eat right, laugh, spend time with family and friends, then you're more likely to be able to consistently put in this kind of effort. I don't think you can or should aim to do much more than 4, but I think a very large proportion of the world isn't capable of even coming close to 4, because they don't or can't manage their energy effectively.

I also agree it is possible to do longer bursts, but that is pretty rare in my experience.

I've read a couple of Tony Schwartz's books which go into this topic more and helped me to rethink my working habits.

...of course, most people (including myself) may be incapable of the intense concentration that a genius like Poincaré could muster. Therefore, it's hard to know how useful this fact is to a typical person.

Implications: People are not going to be great at their second job or at night school. It's probably better to quit a tiring job and find a quiet one where you can study something you want to do with your life.

I've have great success with something similar to The Pomodoro Technique. Alternating activities every few segments helps me go a lot longer than I would trying to plow through on one subject.

1: http://en.wikipedia.org/wiki/Pomodoro_Technique

Relevant read: http://www.your-brain-at-work.com/

"Your Brain At Work" points out, among other things, that the brain is capable of doing much less intensive work (as in, concentration) than most people believe it is.

Oh, it can be done. Just not every day. I once went on a hacking run in grad school that was over 24 hours sustained. I was a gibbering mess for the next couple days, but I think it was worth it.

I wouldn't do it for a job, though. I think that can only be done for love.

I first read about the ~4 hour limit from D.E. Littlewood's book, Littlewood's Miscellany. He recommends "four hours a day or at most five, with breaks about every hour (for walks perhaps)."

Since then I've read of luminaries mentioning this in passing, but I haven't really tried to employ it. (I'm also pretty sure I've seen pg say this is empirically false with YC founders, and perhaps he and axiom are correct)

I'd like to know if there's evidence of this for learning, however, even if it is mathematics.

Littlewood was a talented mathematician; pg is an employer of computer programmers. Unless you are doing original research, which, AFAIK, most YC companies aren't, I see no reason why you should limit yourself to 4 hours a day. (Apart from having a life, but that's a separate debate.)

Another good argument for working from home as opposed to a corporate environment.

Even though a lot of smart people agree that we can only get a few hours of real concentration a day, not many of them link to scientific papers that support this claim. I would agree that the claim "feels right". But in absence of a real experiment, how valuable is this insight really? Maybe useful to keep the idea in the back of one's head, but seems far from a definitive answer.

I imagine that any feasible scientific experiment would measure only a crude approximation to reality. How can you randomize someone to a job and a way of working? Most people are not capable of concentrating for four hours a day, or have jobs that don't permit it.

At best you might recruit some undergraduates -- nearly all psychology subjects are college students -- and have them do some artificial task one way or another for a couple weeks. I find anecdotes from successful musicians, scientists, and authors more persuasive than data from an contrived scientific study.

Those are good points and I agree with everything you said. And even though anecdotes are informative, they may not be enough to make big important claims about how people should manage their mental energy.

I have worked with some extremely successful and famous artists and musicians, some follow the pattern outlined here, some do not. I know one musician who would work for 36 or 48 hours or more without a break of any kind including sleep, so as to complete an idea without losing the thread. The proof is in the pudding and there are many many recipes.

This echoes my experience as well, however I prefer to break it into 3 x 80 minute blocks. The times when I've tried to push myself beyond that for a short period of time (a few weeks) I have ended up sick, ill or entirely unproductive to make up for it.

This is reassuring for me. On a normal day, I only really do so much actual coding and intense thinking, and I usually wrongfully compare it to the crazy energy drink fueled all-nighters (which makes me feel like I'm not getting enough done).

There's a difference between being maximally productive at any given time and coming out cumulatively ahead. The strong claim is to state that one is always net less productive when working sub-optimally at any given time. I doubt that this is true but i suppose it depends on how quickly productivity falls off with strain. I suspect that it's probably ok to work long hours to get through repetitive learning but its best to reserve a fresh focus for your more creative moments.

I spent ~7 hours a day when I was learning C++. I basically had to do this in order to be able to take my course the next semester in college. I went from knowing absolutely nothing about programming, to having a very firm grasp on the subject, and actually being one of the best in my class.

I would have learned a lot with 4 hours a day, but I think the extra 90 hours I put in that month really helped me out.

Malcolm Gladwell said in an on-stage interview I witnessed that he can only write for two to three hours a day. The rest of his time he spends doing less demanding work like research and setting up interviews with people.

From what I've seen, most employed programmers only spend about this much time (maybe a bit more) actually programming.

Gladwell is a poor example.

Why, because he bullshits? I'm not citing him as a scientific authority but he certainly is a prolific author.

Pure curiosity from the perspective of life hacking: Does this mean we can have e.g. 3 tasks parallel in a day where 3x4hours = 12 hours? Say you want to write high quality code, mastering piano and write symphony at the same day, until you reach 10k hour each (=mastery).

No. But it does mean you can do two tasks in a day if one of them doesn't require a lot of concentration or mental effort, e.g. four hours programming and four hours gardening.

Pointless to quantify the amount of time until "Concentration" can be quantified.

I believe that the 37signals guys have a very similar opinion.

Back in the old days when I was in school, I didn't do well with more than 3 classes in a row in college. Not just me though, nearly everyone started with 2 Tu-Th 1.5 hr classes and 2 M-W-F 1 hr classes. That was a full time 12 unit load, but I always took at least 16 units, and sometimes as many as 24, which was up to 3 more classes a week. 16 units was a full time job, the semesters I took 20 and 24 were very special cases where some of the classes were subjects I already knew well or were research project based classes. I think 16 is a good solid load for the typical college student.

When I'm really refreshed and interested and doing well and eating right I can pull all nighters and maintain work quality. I can't maintain this for extended stretches at all though.

For a sustained pace though, I agree completely with Mr. Cook and his sources that 4 solid hours a day is about right.

There are many people who put in substantially more hours and brag about it. A close look though nearly always reveals lots of meetings, busy work, and - these days - surfing the net, playing games, and flirting or shooting the breeze with coworkers. Remove all that and you seldom see more than 4 hours, and almost never 4 hours of solid work sustained for months at a time.

We should also consider whether this discussion is relevant to calls to extend school hours to 7 or 8 or more hours a day in the primary school classroom, as many are calling for. Does Finland, which has fewer school hours than the US, have better results because of it?

Most of that work isn't that cognitively demanding though. If you're reading research papers or textbooks most of the time the really hard parts have been done for you. You just need to follow along.

Also, with most work there's lots of things that need to do that require relatively little concentration once you've made the cognitive shift.

I think the four hour limit applies to design/creative work or work that requires immense attention to detail.

I'd say most people have little in a day that actively drains this reserve in more than a trickle.

If reading research papers is not cognitively demanding, that just means that you're not reading fast enough, or you're not truly absorbing the content. Or are you saying that the speed at which you read research papers is limited by the speed at which your eyes can move?

My impression was that solarmist just holds a book to his/her head and immediately grasps the material.

I meant it relative to writing them.

Reading can be harder than writing, especially if the writing is very bad and you must understand!

I don't know what the empirical evidence from psychology really says. But I think that programming requires immense attention to detail.

> When I'm really refreshed and interested and doing well and eating right I can pull all nighters and maintain work quality. I can't maintain this for extended stretches at all though.

I pull all-nighters regularly to work on personal projects, and managed to push out 4-6 hours of concentration during them after a full day work, but the key to that for me (with the caveat that I'm close to 38, and probably could push through more when I was in school, but on the other hand I know how to pace myself far better):

- I nap 1-2hour in the evening, after dinner, and then take a 1-2 hour relaxation period where I'll vegetate totally in front of the TV or listening to music punctuated by low-concentration tasks such as making a list of what I hope to achieve (with estimates and times at the night where I hope to get to them, which makes for a hilarious lesson in how bad we are at reliably estimating stuff...)

- I pump myself full of caffeine (usually about 200mg, my caffeine sensitivity is really low) and b-vitamins, and "dripfeed" myself sugar.

- I'll use modafinil to retain alertness when I go off for work the next day.

- I'll go to the gym but focus on cardio, stretches and time in the steam room and make sure I have time to take "the slow train" which gives me a 30 minute nap during my commute.

- I'll make sure to take a proper relaxing lunch break. Sometimes I'll go find a park bench and sit and nap or meditate for half an hour.

- I'll make sure to schedule my daytime work to the times that works best for me, and try hard to get some extra high concentration work out of the way on the "before" days, and do more "menial" tasks on the "after" days to ensure the overall effect on my daytime job is minimal (overall I think I actually end up with a net benefit, as the personal projects I work on generally are learning experiences that are often synergistic to what I do during the day).

- I crash totally the next evening - usually going to bed at 8pm and sleeping until 6am the following day. Everything in my scheduling is geared towards keeping me productive the following day too, but with the expectation that the evening will be totally lost.

- If I at any time see my productivity start slipping at night, I go to bed. If I see my productivity start slipping in my day job, I take a week or two break from this schedule and get to bed extra early, because I know if I don't I'll tend to get into a rut where things take longer and tire me out more, prompting me to get stupid ideas about working even longer. And I never, ever do more than one or two of these a week...

In the end, I'm not gaining any hours per se, but the hours I get are hours where I'm more productive (the alternative for me was taking e.g. 8pm to 11pm on evenings where I'd still be tired and generally wouldn't concentrate well at all). The structure of a nap, slowly easing into it, and then focusing totally while the house is entirely quiet works very well for me. Probably isn't healthy in the long term, though. But I need me time desperately to stay sane (got a 3 year old that otherwise occupies all my time at home when he is awake).

It's a massive hassle just to get that extra block of concentrated time (now, if I could afford to slack off the entire following day at work, it'd be a lot easier :) ), but it feels worth it at the moment. When my son gets older and demands less of my time so I get more time to myself earlier in the evening, I very much doubt I'll keep this up (though I've grown attached to taking 1-3 hour naps in the evening and working a bit into the nap instead, so that I'll probably keep up to some extent)

Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact