Here is one reason that you'd expect people to sit on their own too little (from the perspective of a benevolent social planner):
If you are sitting on your own, the expected amount of time before someone joins you depends directly on how much the other party-goers want your company. So at any given moment, being seen sitting on your own is evidence of unpopularity. I think most people can feel that in their bones. So going and sitting on your own is guaranteed to generate some evidence that you are unpopular, the only question is how much of it. For people who aren't constantly analyzing the signaling consequences of everything they do, this may just translate into feeling surprisingly uncomfortable about sitting on their own, even though they normally wouldn't mind a few minutes of solitude.
It would be some work to actually find the equilibrium, but I think that on average you are going to take a hit (in terms of others' estimates for your popularity) from striking out on your own. I'd be interested if anyone actually solves.
If true this is a little bit weird---you take an action that we'd expect popular people to take more often, and then people update negatively about your popularity? The trick is in the step where people have better ability to observe "who is sitting on their own right now" than to track the exact sequence of events that occur. For example suppose people scan the room once every few minutes. Then they can notice someone sitting on their own, but if they see a group of 2 people they don't know who joined whom and so can't tell whose popularity they should update positively about.
To the extent that's an important dynamic there are lots of possible fixes.
One simple idea is to designate a space for forming new conversations that isn't visible from the rest of the party. If I want to start a new conversation with someone random, I go to the designated room. If it's just me, I do some math or browse the internet or whatever (personally I don't mind solitude, but do mind awkwardness). When other people join, then we go somewhere else and it's business as usual.
Of course you could do this better with a machine. I can pull out my phone and press the "new conversation" button, get told if someone else has also pressed "new conversation," and then start a new group with them. This would be an easy app to make (everyone enters their name and sees a checkbox, when two people within 100 feet check the box, their boxes get unchecked and the second person sees the first person's name). I would try it.
(ETA: a bolder and sillier solution is to have it be obvious who started the conversation even to observers who quickly scan the room, e.g. because the first person takes a designated sitting-on-your-own seat. Then in theory the positive update from being the first participant in a happening group should offset the negative update from sitting on your own.)
Often the bar is very visible though, which makes it trickier. I think outside might be a good option.
But the point is you might not be sitting and waiting alone, you might just be getting food. (This intuitively feels less bad to me and I’ve in fact done this thing, although if I end up spending too much time there I think it becomes obvious enough to feel bad again)
If the quality of conversations declines with size, here is one reason that groups might get too large (from the perspective of a benevolent social planner):
Conversations vary in their desirability---whether because of random drift in topics, the presence of fun people, access to the comfortable seating, or whatever. So by default some conversations will be better than others. This is partially visible from outside, whether by observing how much people are laughing, looking for the cool kids, or just gravitating to the couch.
If any conversation looks better than other conversations, then selfish conversational participants will preferentially join that conversation. We'd expect this to continue until the marginal party-goer is indifferent between each of the conversations. This will cause the good conversations to become larger and larger until they are no better than any other conversation.
To see how this leads to a problem, suppose that you have a house with a large number of spaces for conversation, one of which is nicer than the others---and simplify everything maximally, assuming that all conversation participants are interchangeable and that adding more people really just makes discussions worse (ignore the fact that you would obviously never throw a party in this world).
Then you end up with a bunch of 2 person groups, and one N person group using the nice space, where N is just large enough that the N person conversation is no better or worse than one of the 2 person groups. The net effect is exactly the same total welfare as if you had no nice space at all.
Of course the same thing happens if you add one person who is the life of the party, improving the quality of whatever conversation they are in. If you add just one such person, then the group containing them will grow until it is large enough to totally offset their value add.
The effect is less stark once you add enough cool kids and nice spaces---eventually a rising tide lifts all boats---but in general this kind of dynamic could lead to a leveling down to whatever the quality of the "reservation conversation" is, obliterating any gains from nice spaces, particularly fun people, or conversations that happened to go in a really interesting and fulfilling direction. (I'm not really sure about this last one, since if conversations sometimes go in an interesting direction then that also increases the expected value of starting a new conversation.)
To the extent that this is an important dynamic, there are possible fixes. A very brutish solution is just having a strong norm against joining conversations once they reach a certain size. If you could exogenously determine social judgments, you could deem it impolite to join 4-5 person conversations, taboo to join 6 person conversations, and good etiquette to leave 4-6 person conversations unless you are feeling particularly engaged.
Person enters the room, or exits a conversation. In descending order of preference, they can either (1) talk to someone who is sitting alone, (2) join an existing conversation, or (3) sit alone. But because people don't want to be the first person to seed a new conversation, there aren't many people by themselves to make 2-person conversations out of. So, to fix the incentives...
When you start a conversation with someone who was sitting alone, give them a dollar. (Not entirely serious but not entirely joking either.)
I agree that this is the key dynamic making this happen. Except it's worse than that. Imagine that you enter the room or exit a conversation. Out of the options listed above, you are indeed probably going to pick #2. But which existing conversation will you join? Unless you're going out of your way to keep group size small you will likely be influenced by two things: (a) prefer a group containing someone you know/like; (b) prefer a group that looks like it will be glad to accept a new person. Both of these favour larger groups over smaller. So larger groups will grow faster.
When I'm at a party and having a good conversation with the right number of people, I try to move it elsewhere to preserve the set.
My first reaction was that this discussion focuses too much on sitting on your own, or inviting someone else from your group to move elsewhere. After all, large groups can also shrink when people leave a large group and go join a smaller group.
But on second thought, forming new groups is necessary, otherwise the number of groups will just keep decreasing and so they eventually will end up large. So in fact it seems very important that you can either split off subgroups or else go sit on your own.
I think in some spaces it is much easier for large groups to fission into small groups and then drift to different spaces. This might be an important consideration for party spaces / layouts.
Other random frictions:
I also thought that at first, and wanted to focus on why people join groups that are already large. But yeah, lack of very small groups to join would entirely explain that. Leaving a group signaling not liking the conversation seems like a big factor from my perspective, but I'd guess I'm unusually bothered by that.
Another random friction:
I don't know you personally, but your description reminds me of several people I know, they are catalysts and centers of attention at every gathering, even when trying to hide. If you are one of those, then you have observed a... KatjaGrace effect. Have you noticed if others who had decided to sit alone attracted more than one or two people, if any at all? Or did they end up sitting alone until they got bored and left or joined a group?
Agreed. I've met Katja and can confirm that she is more interesting than most people. If she wants to socialize, this initially creates a situation of increasing returns to scale. But a conversation with Katja and a slightly larger-than-optimal number of people is often going to be more interesting to join than a conversation with the optimal number of non-Katja people. So in general, conversations with Katja will be oversubscribed relative to the level that makes for the best conversation.
Aw, thanks. However I claim that this was a party with very high interesting people density, and that the most obvious difference between me and others was that I ever sat alone.
I personally do not find this dynamic confusing at all. Seeing as this is not obvious to other people I'll try to explain how I understand it to work (and because I like the idea of cats and pineapples I'll stick to those):
1. You need to start with cats, and the right cats: Two people who have each other's undivided attention makes for a much better conversation than starting in a group. And obviously these two cats need to have something both of them have common knowledge about in order to have a conversation.
2. Soon you'll start to form a pineapple: The conversation of two cats usually works by each cat adding information the other doesn't know and find interesting. You're sooner or later bound to find some other people walking by at your party who also want to add in on the conversation. The amount of these people determines the "size" of your pineapple aka group.
3. The choice: Now, you could start pushing other people away when they want to turn your pair of cats into a pineapple, and that may be a reasonable thing to do if people in your pineapple are just pretending to know things or aren't interested. However, if this is not the case it is a plus to be in a pineapple.
In general this dynamic from cats to pineapples is what creates things like special interest groups and in general how communities form. The internet is simply making step 2 easier than ever.
I went to a party. Arriving guests got stickers: cats and pineapples. Pineapples would have to talk in a big group, cats would be pairs and trios. Everyone knew the cats had it better.
I got there before the game. When the fifth person came, I broke off and sat alone. He sat with me. More people wandered over, and soon we were six, seven, eight.
We talked about how small groups are better, and laughed at our big group. But what can you do? It’s hard to invite your preoccupied neighbor to more intimacy with an audience of seven.
I got up and stood alone on the other side of the room. A friend followed. Success. But normally I wouldn’t have walked. And normally he wouldn’t have followed. Our group grew. Three, four, five..
The game began. I was a cat. It was good. What is basically going on in the world? What are different people’s experiences like? What do I get out of knowing this? What is romance? What romantic advice does one give a radically inexperienced person? How good was my previous five year romance with my conversation partner? Is it better to love or to be loved, if you have to pick only one, forever? How does one escalate conversational intimacy? Should one do that, or just jump in?
The game ended. How would we decide which was best? Each of us only saw one side. Oh well. A show of hands. Repartee. Almost everybody likes small groups. Nobody’s mind was changed by tonight. Perhaps this large group wasn’t up to scratch.
For a magical moment, this largest group of all—a space of circles, paused and opened up, calling out to each other—was a kind of good that I hadn’t seen below.
We collapsed back into party. I talked to a friend next to me. What is fun like? She told me. That was surprising. What is love like? Our group grew out to block the doorway. I had some work to do, so I took a walk.
I came back to two giant circles. Exclamation. I sat alone. Eventually a friend sat down. What is fun like? The same as for the other friend. Interesting. Our group grew. Two, three, four. Six.
I crossed the room and sat alone. A friend joined me. The room joined us.
Was this really what nobody wanted?