I'm asking them to help me draw precise lines around their concept in thingspace, and they're going along with it (at first) until they realize...they don't HAVE precise lines. There's nothing there TO understand, or if there is, they don't understand it, either.
There are no precise lines that can be drawn around anything. So if this meant that there was nothing to understand (which it does not), there would be nothing anywhere to understand about anything.
Basically what they are saying is this: concepts are something which are useful to us. They are not, and can never be, infinitely precise. You are overthinking if you are attempting to make them more precise than is needed for their usefulness.
Some people actually don't use their supposed concepts in load-bearing ways, and are just telling you what the party line is according to them. You're not expected to think at all, you're expected to respond with an improve move - the norm is "yes, and".
For example, the Sorites paradox is what you get when you start overthinking what a "heap" is. (Start with a heap of sand. Take away grains one at a time, until you don't have a heap any more. Exactly which grain of sand was it that made the difference between being a heap and not being a heap? The correct answer is "Who the hell cares, we can still call something a 'heap' and be understood without actually needing to be able to handle the weird edge cases.")
I think there's another option to look for.
Sometimes the way you're thinking makes assumptions you're not noticing about how to draw lines in the first place. And they see that, and they see that your assumptions are blocking you from understanding. But they don't know how to explain it in your paradigm. Which means it's easier to ask you to suspend your way of trying to understand and just try something different.
A silly example is with bike riding. Someone who never rode a bike before can study physics all they want to, and dive into neurology and see how learning works in principle and how that interacts with trying… but most of that basically doesn't matter. You just have to get on the bike.
But I see this show up in aikido too. People want to understand how to do a certain movement, but some people insist that they understand through words and principles, and those people are the hardest to teach. I have to slow them down, ask them to stop trying so hard to think of it that way, and draw their attention to their bodies instead. Then their bodies can teach them new nuances of experience.
I really respect the power of analysis. I find it annoying when people who think vague thoughts defend their status and worldview by trying to make me dumber.
But from the inside, sometimes that's what it'll look like when a person who is in fact seeing a dimension you're not even operating in is trying to point that fact out to you.
This. It took me years to understand this, but it's true, and vital to proficiency in most areas of endeavor.
The trouble with "overthinking" is that it's all to easy to try to oversimplify, or to frame a problem in terms that make it unnecessarily difficult. Martial arts are a good example. My experience with aikido is minimal, but at least in jiu-jitsu, knowing what a move feels like provides the data you need to actually use it, and in a form that can be applied in real time. Knowing verbal principles behind the move, on the other hand, almost invariably leaves out important pieces, and even when your verbal understanding is more or less complete, it's too slow to actually use against all but the most cooperative opponents.
Of course, that's with a physical discipline. Going back to the OP's question, how can overthinking be harmful when trying to understand a purely abstract concept, or how can a concept be understood with less thought rather than more? Well, as Bound_up says, it's impossible to understand a concept without thinking. But the kind of thinking is essential.
For example, I struggled with learning calculus for a while. The teachers would explain various tools that could be used to take a derivative or integral, but it wasn't clear which tools to use when. I responded to this by trying to create a rigorous framework that would reliably let me know when to use which formulas. However, there simply weren't enough consistent, reliable patterns relating a certain type of function to a given formula for differentiating it. Everyone said to "stop overthinking" calculus, but I figured there had to be rigorous algorithms governing the use of u substitution vs. integration by parts, and that the people telling me to just relax were sloppy thinkers who didn't generally understand concepts beyond rote learning.
What ended up actually working, however, was accepting a more ad hoc approach. Creating an algorithm that could tell me what tools to use, first time, every time, was beyond my capabilities. But noticing that a function could be manipulated in a certain way, or expressed in a more tractable form, without expecting that the exact same process would work the next time, wasn't actually very difficult at all. It was a bit frustrating to accept that calculus would consistently require creativity, but that's what actually worked, when my overthinking turned out to be oversimplification.
I agree, and wish to state for the record, that to be told one is "overthinking" is about the least helpful (certainly least actionable) criticism one can receive.
In many cases, the one who says this wishes to communicate that their knowledge is tacit, and to contrast this with the other's attempt to use explicit reasoning. But tacit knowledge does not magically appear when you stop "thinking"!
Another perspective: they use "overthinking" as a hint at some mental motions, while you interpret it normatively as a thing-out-there-in-territory.
A reasonable interpretation of the mental motion of "not-overthinking" DOESN'T mean that you use net less thinking or intelligence. It means that you use different kinds of mental machinery to think (e.g. more S1 etc.)
This is probably the more common use of the term "overthinking" than your first paragraph. You're putting more thought and analysis into something than that something supports. Further analysis and data will lead to not just delays (your first thought), but worse outcomes, as you'll start trying to override your instincts with inappropriately-weighted data.
Where to eat as a group is a good example. You can easily overthink this even if you have plenty of time, and end up going someplace you're modeling as the center of a groups desires rather than someplace the group actually has fun at.
Overthinking can be quite interesting if both parties are interested in target of the discussion. You might be talking to the 'wrong' people.
well, it's easy to "overthink" when the topic/problem is poorly defined (as well as "underthink") - which is the case for 99.9% of non-scientific discussions (and even for large portion these so-called scientific ones)
Related to http://lesswrong.com/lw/1mh/that_magical_click/1hd7
I've NOT been confused by the problem of overthinking in the middle of performing an action. I understand perfectly well the disadvantages of using system 2 in a situation where time is sufficiently limited.
And maybe there are some other fail modes where overthinking has some disadvantages.
But there's one situation where I'd often be accused by someone of "overthinking" something when I didn't even understand what they might mean, and that was in understanding concepts. I would think "Huh? How can thinking less about the concept you're explaining help me understand that concept more? I don't currently understand it; I can't just stay here! Even if you thought I needed to take longer to try and understand this, or that I needed more experience or to shorten the inferential gap, all of that would mean doing more thinking, not less."
Then I would think "Well, I must be misunderstanding the way they're using the word 'overthinking,' that's all." I'd ask for a clear explanation and...
"You're overthinking it."
Now I was overthinking the meaning of overthinking. This was really not good for my social reputation (or for their competency reputation in my own mind).
.
Now, I think I got it. At last, I got it, all on my own.
I'm asking them to help me draw precise lines around their concept in thingspace, and they're going along with it (at first) until they realize...they don't HAVE precise lines. There's nothing there TO understand, or if there is, they don't understand it, either. Then they use the get-out-of-jail-free card of "You're overthinking."
.
Honestly, most nerds probably take them at their word that the problem is with them, and may be used to there being subtle social things going on that they just won't easily understand, and if they do try to understand, they just look worse (for "overthinking" again), so this is a pretty good strategy for getting out of admitting that you don't know what you're talking about.