+1 to John and Ray for this; my experience is very similar to John's. Here's a relevant old post from me, where I was trying to gesture at the importance of a cluster of things around or similar to your #3, as distinct from #1 and #2; http://acritch.com/boredom/ (Title: Boredom as Exploratory Overhead Cost.)

This is actually a lot of what I get out of meditation. I'm not really able to actually stop myself from thinking, and I'm not very diligent at noticing that I'm thinking and returning to the breath or whatever, but since I'm in this frame of "I'm not supposed to be thinking right now but it's ok if I do", the thoughts I do have tend to have this reflective/subtle nature to them. It's a lot like 'shower thoughts' - having unstructured time where you're not doing anything, and you're not supposed to be doing anything, and you're also not supposed to be doing nothing, is valuable for the mind. So I guess meditation is like scheduled slack for me.

Curated. This post articulates something important that I feel like I wrestle with every day. There are strong pressures to generally do more. There's just so much value you achieve if you did more things! But it's maybe something of a trap. If you take on too much, you lose the ability to notice which things most need doing.  

Example:

I have a couple of positions I need to fill at my work. I’ve been off on holiday this week and it occurred to me that I should change one of the roles quite a lot and redistribute work.

I’ve had this issue for a few months and while in work I’ve been a bit overworked to actually take a step back and see this opportunity.

Completely agree with you and John here. When I'm overworked, I often notice that what I'm feeling the most is a need to reflect on my current trajectory and do some meta-thinking.

Another way of phrasing it is that slack actually lets you react when you notice confusion, instead of having to let it be.

This also fits well with the problems with too much slack: for me it's not doing too much rest but doing too much meta-thinking instead of actually doing things.

I agree with the basic setup, although I think their is an optimal amount of slack to maximize the effectiveness of noticing subtle things. To notice these things you need experience, and time to reflect on it. Too little time is probably the main bottleneck in most cases, but in some cases it will be too little experience. IE Hiring a hundred slack-specialists to hang around with 100% slack-time is not likely to be productive.

Maybe I am mis-reading you, but I think of the "noticing subtle things" is something like, after you put out all the fires you later think "many of these problems seem to stem ultimately from the way that..." or whatever. But without having seen the problems that could not have happened.

for me, its even more Slack for the mind. And i would have initially associated the benefits with creativity.

Im a CEO and have lots on my mind. i can use up all of my worktime to put out fires,... at home 3 kids, and lots of hobbies. So my mind is not allowed to rest it seem.

I usually had the most creative or problem solving revelations when i was traveling in my car for hours. I recently started with audiobooks while traveling. This affected me heavily, creativity and revelations reduced drastically. I also noticed this, when i switched from scientific work on a university to a business job. Time to think, reflect can only be found in slack time for me.

Same applies to workforce, if they have no slack i receive 0 suggestions for improvements outside their job. As soon as they are little bit idle, they start to think outside their box it seems.

Just wanted to share this, as thats the first thing i was thinking about but i would have put it differently.

This reminds me of focused/diffuse thinking.

Focused thinking is rule-based, mechanical, goal-oriented, precise, strictly sequential, logical, works in small steps.

Diffuse thinking is creative, open-ended, creates long connections, produces leaps of insight that are impossible in focused thinking.

The best example of this is solving math problems. Paradoxically, it requires to alternate between these two modes frequently and fervently -- something that people generally struggle to do. After all, most people either think like bureaucrats (like me) or they think like artists. But in this case, and in any other complex endeavor, you need both.

Different life phases require different focused:diffuse ratios. The primary variable for that is slack.

I think this idea absolutely hits the spot.  A well worn saying is that good workers are generally promoted beyond their own capability. This is true but often because they get bogged down with meetings, fire-fighting, admin, pleasing the (Wo)Man etc.., lots of reactive stuff. My experience exactly. I changed jobs, gave up management, went down to three days a week (gaining two days of slack), declined as many meetings, as I could getaway with and became more productive than any time previously, largely because of having time to let ideas slowly gestate, play with stuff, notice the subtle things, and thereby make progress in useful directions.  I swear my employer effectively gets 5 days out of me. I should be paid more!

I feel personally addressed and a little offended, so thank you for the reminder. It's too easy to slip into too much of #1. I don't think that is necessarily bad but I do want to work more on problems I don't understand.