"Chaotic" productivity explanations:

I read a book called "The power of full engagement, manage energy not time." in which it explains that studies show that a 15 minute break every 90 minutes or thereabouts increases productivity. There are other studies with results like this - for instance, Ford's study that showed that his workers, if putting in 60 hours a week, would actually lose productivity so that after two consecutive weeks of this, their productivity level would dip below 40 hours. If I remember correctly, the clue to why this happens is an increase in errors. You're probably familiar with the labor laws that correspond - I read somewhere that they were based on these discoveries.

Not sure whether there are any theories about why the brain needs to rest, but there's probably some kind of important purpose for this.

I have experimented a bit with my needs for rest and I've discovered things like:

The more I am enjoying my activity, the longer I can focus. Might this be similar to what's described in Overcoming Bias's new "Sleep Is To Save Energy" article which explains that some people seem not to need as much sleep because they have more energy. I realize "energy" is kind of a curiosity stopper here. For a guess at what it means, I'd say possibly more neurotransmitters like serotonin and dopamine. Though it's obviously high-risk to mess with brain chemistry, it isn't high-risk to learn stress reduction techniques or increase your enjoyment of work and see if those make a dent.

Sometimes if I'm experiencing stress-related burnout, simply laying down in a quiet and dark environment for 20 minutes or so restores me. Note: I am not talking about sleeping, the objective is to avoid stimulation. This is especially good for stress-related burnout.

I've observed that stretching restores a decent amount of functioning during stress-related burnout. I don't know the reason for this but I've wondered if it had anything to do with muscles releasing chemicals when stretched or stretching affecting circulation.

I encounter little "snags" throughout my day - I'm wondering things like "How do I apply my philosophy to this scenario?" or "There's a new piece of information, I wonder if I will have to stop doing things this way after I investigate it." which can create a necessity to do some simple activity that allows for processing.

Sometimes a reminder keeps surfacing in my mind over and over again which interferes with my concentration so I get fed up and do something with it.

Sometimes I'm trying to remember something, or come up with an idea, and for some reason, doing something completely different for a short while causes a memory or idea to pop up suddenly.

I get a desire to exercise certain parts of my brain that haven't been exercised for a while (this often results in a need to do something visual after programming all day). The brain seems to have built-in motivation to do things that will cause you to learn optimally (From the book: Flow: The psychology of optimal experience) and to avoid things that won't. So it occurs to me to wonder if this is it's way of motivating me to be adaptive by avoiding specializing too narrowly.

I remember hearing a theory that dreaming is your brain's way of organizing your memories. I've read other theories since then which contradicted it and I'm not really sure what to think of them, but it occurs to me that there may be regular maintenance activities the brain must do to stay organized and optimized.

Variations in exercise may affect things: "The power of full engagement" explains that if you exercise 20 minutes twice a week, you'll get a 15% boost in productivity.

In addition to assuming that your productivity was chaotic, it is also a mistake to assume that the brain works in such a way that it SHOULD be able to do an arbitrary activity constantly for an indefinite time period. This may be a remnant of Puritan work ethics that have made their way into our culture, which are definitely not optimally productive if you look at the research.