I agree! I'd also wonder why so little information is given in hours. We have that likely horizon of mastery at 10k hours and we have a soft limit of "usability

I agree! I'd also wonder why so little information is given in hours. We have that likely horizon of mastery at 10k hours and we have a soft limit of "usability" at about 3k hours. But maybe the thing is, nobody really counts. Like, I can tell you when I started to study my major, which led me to spend a lot of time on programming, taking it serious for the first time. Now I work full time as a software developer but do I spend 30 hours, or 10 hours, or 50 hours programming a week? Can't tell. There are lot of things involved, no matter if you're a student or a full time worker. Not all of them count. And going back to your Japanese example. Sometimes the drunken two hours you've spent in a Karaoke bar trying to impress local girls was worth much more than the previous 10 hours study session because these two hours were marked as important memories by your brain and the previous ten hours were boring. It's really hard to calculate, right? Also that study which came up with that 10k hours for mastery stated that many people very much overestimate hours spent, which from feeling I would agree. Like, since I work full time I don't believe any more that people really spend 40+ hours working. It's closer to 20 or 30 hours depending on the person. The rest is spent smoking, chatting, fighting via email, reading HN. And from own experience I also know that 12 hours of doing nothing can be just as tiring as working hard. ;)