On your quiz, the average answer is &quot;3-5 hours,&quot; and this squares with recent research suggesting that in an 8-hour day, mind workers are doing actual work about 3 1&#x2F;2 hours on average. The rest of the day is spent on snacking, gossiping, Facebook, etc.<p>I&#x27;m a highly motivated independent developer and writer, and I&#x27;ve been studying my own work habits to try to become more productive. I use toggl — <a href="https:&#x2F;&#x2F;www.toggl.com&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.toggl.com&#x2F;</a> — to track my time throughout the day. I&#x27;d work 12 hours a day if I could, but I can&#x27;t. I run out of gas after 2 hours, 3 hours — and sometimes 8 hours. My limit on tedious, fussy, boring tasks is about 2 hours, after which I&#x27;m not much good for anything. My limit when I&#x27;m writing a book is 3 to 4 hours. If I&#x27;m building something out of code or working in Photoshop, sometimes I get addicted, and then I can go 8 hours. Addiction seems to be the only thing that gets me close to being as productive as I&#x27;d like to be. Sadly, I can&#x27;t choose to focus only on the types of tasks that I&#x27;m addicted to.<p>My sense is that most people — probably including your boss — have never measured how much cognitive work they themselves can do before their brain is fried. I&#x27;m talking about real work, not meetings. Meetings use almost no brain glucose at all, so are a way to pad &quot;working&quot; hours without increasing fatigue substantially. I&#x27;m convinced this is why meetings are so popular in corporate America.<p>As long as no one is measuring, it&#x27;s easy for everyone to kid themselves that they&#x27;re good for 8 hours and that everyone else should be, no matter how unrealistic that may be.