What does accepting an answer actually convey (2015 edition)?

Question

From time immemorial, prominent placement for accepted answers has been baked into Stack Exchange. The reason is that, by accepting an answer, the OP is saying "I did that and it worked for me; I don't need any more help". That signal is valuable. So we pin that answer to the top of the list, so viewers will see it first. (Except for self-answers, because of concerns over gaming the system.)

There have been lots of meta posts about whether this pinning is actually a good idea when there are other, higher-voted answers. No really, lots. For example:

• Can we exempt downvoted accepted answers from getting the top spot?

• Let's move some negatively scored answers from the top spot (see links there to several more)

• Shouldn't the answer with more votes be above the accepted answer?

• Keeping special status for Accepted Answers without sticking them to top forever?

• The accepted answer concept is not useful for sites that are not about problem solving

This cluster of problems has been troubling bluefeet ♦ and probably others on the team. Discussions of moving the accepted answer are controversial, even if we provide ways to jump to it.

All of this raises what, to me, seems a more basic question that we ought to answer first: what does it actually mean, today, and in practice rather than in theory, when somebody accepts an answer? 'Cause that's the signal that we'd be disrupting if we change how pinning works.

I'm dubious about the theory, in two ways:

• On many sites that weren't even a glimmer in Joel's eye when he launched Stack Overflow, answers aren't actually testable or verifiable. I think that sometimes people pick answers that worked for them in some fuzzy way, and other times they pick answers that they like for their own reasons. Subjective-leaning sites can be especially prone to this (as previously noted).

• On the parts of the network I frequent, people still answer questions that already have accepted answers. (I had been under the impression that this doesn't much happen on SO, but I was wrong. More on that in a bit.) So the fact that the original asker has been helped might not mean much to the community, which is supposed to address the question for future readers too.

I don't know how to systematically investigate my first point, but we can science the second one. I used this SEDE query (h/t msh210) to answer the question: how often do questions with accepted answers get new answers? (The query reports separately on positively-scored new answers, but this isn't a big difference on most of the sites I tested.) Deleted answers don't count in this query.

I ran the query on the top five sites by number of questions and a smattering of other non-tiny sites. I was surprised by what I found:

• Approximately half of the questions with accepted answers got newer answers on: Stack Overflow, Mathematics, Ask Ubuntu, English Language & Usage, Emacs, and Chemistry.

• Approximately one-third of the questions with accepted answers got newer answers on: Super User, Server Fault, Programmers, Mi Yodeya, and Skeptics.

• I didn't find any in my sample with drastically higher or lower proportions.

That's a lot of answering for questions that the OP said he's done with.

So, to restate the question:

What signal do we intend acceptance to deliver? What are people who see the pinned answer with the green check mark expected to do with that information? How should it modify behavior?

---

Here's the data I collected:

Site            Qs w/accept     w/newer A       A upvoted
SO              5891756         2860654         2277478
Super User      131019          47618           36618
Server Fault    107697          34887           27483
Mathematics     279096          169396          150686
Ask Ubuntu      70594           35399           27346
English         34726           17995           15557
Programmers     27608           9788            8740
Mi Yodeya       6342            2532            2362
Chemistry       5197            2529            2331
Skeptics        3116            945             871
Emacs           2787            1586            1450

Answer 1

There's a number of things going on here.

The accept mark has always been an extra bit of signal from the question author. In most applications, it generally means this worked best for me, or led me to discover something else that worked. It's designed to be a beacon for future visitors, because the question stops belonging solely to the question author the second that they submit it. That's a key thing.

While the OP is free to accept an answer, which does sort of tacitly imply a sense of finality - there's positively no reason that others should hold off on posting additional answers that cover additional ground, or cover things that have been previously explained in a much better way. The question author might be done, but we try to optimize for everyone else that has the same or similar problem. If you have better information than other answers provide, post it.

What do you do with it? Well, that's up to you. It's a beacon, kind of like a hobo sign - it means someone once appreciated something and left a mark. It's up to you to check out the other answers, and pay particular attention to more recent answers, if they exist, that might contain newer information more relevant to your scenario.

The fact that it influences the sort order, and that old answers don't always age particularly well for a number of reasons (which is what we were looking at) is another matter entirely; the accept mark just further complicates that because losing that tiny bit of extra signal would be a bad idea. Even really smelly accepted answers are often educational, in a "do as I didn't" sort of sense.

We could come up with a number of schemes where the sort order changes based on signal that we get from votes, but that would mean piling even more debt on a heap of complexity we're trying to assuage in the anonymous / new user experience. We'd end up making things a little better for people that have a good understanding of how things work, but even more confusing to those that don't.

Anyway, I digress - the signal itself hasn't changed much over time, it's just the fact that it doesn't age particularly well that's been coming to light a bit more often as of late. Ask Bluefeet what "complicated" means and she might pull out a sharpie and draw a check mark on you :)

Answer 2

To start with, in my experience this reason given in one of the posts referenced is just wrong:

The asker has decided it works

In my opinion and going on my own experience (mostly on SO), OP doesn't always test the solution provided. And if they did, they often pick the first, highest-voted or shortest answer (usually all three of them). Often that solution just gives a quick fix with not much more information. And that is what OP wants: just a solution, not the solution he wanted to have a few years later on (most users don't care).

That means that the better, more explaining and eventually late answer doesn't get any attention of OP, but it does from the community who recognizes the better answer from their experience. To me, the accepted answer just means 15 reputation, nothing more. It is often just meaningless.

What is should mean? I am not sure. Accepting seems the wrong word if you ask me. It was the answer OP likes best at the time he was interested in it. Most of them don't bother later when other answers come in.

In the ideal world, OP takes ownership of the question and maintains it, but that is far from the current practice.

If I am looking for an answer, I usually trust the community better than OP, so I start with the highest-voted answer, not the accepted one.

Answer 3

When accepting an answer, what I am saying is not always "I did that and it worked for me; I don't need any more help".

Oftentimes, it is:

I accept that this answer has done as much to help me as I think is fair to expect, given the question that I asked, so I think you deserve to be rewarded

I suspect this applies to many answers that I see accepted by others, and is irrespective of whether the question asked is good or bad.

I think that, in practice, accepting is used to reward not just the result, but also the effort to assist.

The instant 15 points is part of that reward, but what can gain many more reputation points for a good answer, is occupying that top slot for a period of time, and that is currently set to forever. The top answer is sometimes the only one I have time to read, and if it sounds reasonable then I'll upvote it.