At least two, never less than three and more than four to sustain a group chat.
First a little bit of theory on communication: basically the term communication refers to the act of exchanging information. Information can be basically anything: words, speech, images, jokes, sad stories and so on. The way of transmitting information can also be done in one of various ways. The most dominant ones are verbal and non-verbal.
For interpersonal communication, two people are always needed: You can't exchange information interpersonally if there is no one else beside you. So in order to start a conversation, you at least need two people. If you have not two people, there's no communication and no chat. So a basic number of two people is needed to form a communication.
Building on that, you need three people to ensure that the other two people don't just exclusively communicate with each other. The concept of exclusion even works in the internet and especially in anonymous chats.
However, the magical number is four to fully sustain a chat: if there are four people, there are twice as many ways to communicate as with only three people. The means of levering the possible way of communication can only result in one thing: more information is exchanged at the same speed. This means that the chat is becoming more lively and lively. In big chats, there is not even one second of rest - messages are pinging up at a steady steam.
Communication partner | Possible ways to communicate
2 | 2
3 | 3
4 | 6
A more thorough explanation of what I mean:
As communication always needs at least two people to work, you can easily do your math to calculate the possible combinations of people communicating. Applied in the real life, this often is not the case as often groups are formed and the groups themselves communicate with each other. However, theoretically one of four people can communicate with three other. Needless to say that user can't communicate with three people at once practically (or to define it better: they can't properly communicate with all three people at once). So the possible ways to communicate means the sum of possible combinations of the chat participants.
Summarised this means that you at least need two people to have a minimum flow of exchanging information, three people to make sure that the conversation isn't becoming too two-sided and four to successfully invoke a good and healthy group chat. But that's all numbers and theory and quite often theory are nice words but don't exactly work in the real world. As I do believe that this system works, I can also say that it has major, if not even disastrous, flaws.
I myself used this formula for a lot of communities and I saw that it can work just fine but it can all be turned by just one single person.
As I said, the upper part is theory and theoretically we all can communicate at our best at all times, however, we know that this isn't true at all. The keyword here is emotions and they can turn the previously mentioned rational and objective rule around in less than seconds - I even claim that one person doesn't even need to communicate at all to silence a just seconds before lively chat.
It boils down to the point that's all about at least one person who can turn your chat into a heavenly exchange point of information or to create a void of non-existential communication.
If you have one user who is really cherished to communicate with anyone and to get to know people (namely strong extroverts), you can be assured that your chat only needs two people to function properly and not fizzling out. But this only works as long as this user is present. The user "allows" other users to effectively, efficiently and easily opt-in and opt-out of conversations as he gives everyone a warm greetings and tries to cultivate conversation. This means as long as there are two people and one of them is him, you have very lively group chat where other users can easily join.
In our real world, we often call such people moderators. Moderators in our real world are often present at big talk-shows where they moderate conversation and communication to discuss particular topics - and basically this is no different compared to your chat on your website.
But if you have moderators, there must be something that is the total opposite. Let's call it here a judge. In the real world, a judge has the power to silence a court room as he has the authority to do so. You may now say that an ordinary user isn't meant to have such power but this is only a formal level. Judges in your chat room don't need to have formal power but informal power. This can be anything. They can create a pseudo-authority by literally judging anything to the point of ridiculousness so that no one wants to participate anymore. Or they behave in a disgruntling and disturbing yet not rule-breaking way and everyone is annoyed to death and avoids to chat in your chat room.
This all is based on emotions. There are people who have a naturally positive presence, some who have naturally negative one and basically everyone can have a good and a bad day. Even you could be the reason that the chat isn't working as you somehow are emotionally down and drag down the whole chat. (Note that users aren't stupid: If you normally use a lot of emoticons to express your emotions and suddenly you don't use anymore, you can be sure that a lot of people jump to the conclusion that you have a bad day (if that's true or not, doesn't matter one bit) and could probably avoid communicating with you entirely - hence you don't even get an opportunity to explain yourself.)
Coming back to the original sentence "At least two, never less than three and more than four to sustain a group chat.", I do claim that it works but I also state that it can be overturned by just one person.
So my basic approach is to ensure that I only create a chat room if these basic requirements are met and if I know at least one person whose strongly desire is to communicate. This can be a normal user or a team member. These requirements help immensely (at least in my experience) to cultivate a lasting group chat.
On a side note: You should be aware that nothing is worse than chat room who is silenced for too long. This is damaging to every kind of community.
A basic desire of a human being is to communicate. We are designed to share information as this is the only way to ensure our survival. Nowadays, this doesn't seem to important but it still is, always was and will never not be. Communicating is the only way to share information and without information there is no way to possibly advance technology and society. Besides food, water, sleep and bowel movements, communication can be considered a very basic need to fulfill.
To relate this to your situation now: Generally everyone is keen to communicate in your group chat as long as some requirements are met.
- At least one person is present. Without a person, there can't possibly be a communication.
- At least one person is ready to communicate. Physical presence doesn't mean that a user is mentally prepared to communicate - they could just feel like "Nah, not now".
- There is the knowledge that there is a "basic liveliness". Even though nobody answered you now, you can expect an answer the time you return.
Silence is death to all of these requirements. As communication is a basic need, we tend to fulfill it if we need it. We strive to fulfill it any time it arises. As soon as your chat room is silent for a significant time (read rule three again: as long as there is a "basic liveliness", this situation doesn't apply), few user are willing to break the ice as breaking the ice...
- seems time-taking but the need needs to be fulfilled now or in a few minutes. Simply, there is not the time to break the ice now.
- is not worthwhile, you could easily join another group chat you know.
Users will always go the way of the lowest possible resistance and this applies to communication as well.
Extending to the reasons above, there is an even more striking point to avoid chatting in a group chat that is silent. Following questions come to my mind if I see a silent room:
- Are there even users?
- (If I know there are users.) Where are the users?
- (In case I know that there was communication and the users are still present.) Why did everyone go silent? Did something happen?
You see that a silent room is pretty much a temporary death sentence to a chat room. But even in this case a strong-willed communicating individual could turn the sides in an instant.
To give a insight I earned in my past years: new users are the perfect way to break the ice as they are still "pure". They don't belong to the community yet, so they don't fear to break rules as the "newbie" bonus still counts. If a new user arises, there also is the opportunity for seasoned users to communicate with someone new, possibly exchanging completely unknown information. Something everyone is keen to do.
For the term of "basic liveliness":
To elaborate further of the term of "basic liveliness", as there sure will be questions, I will first give an example. Imagine a very big community with thousands of users. This community has short-box. This is a kind of chat room where everyone can post but only is allowed to use a fixed amount of characters. The community is so big that you know that there will be a message every few minutes. But suddenly, there is no message in over an hour! The basic liveliness is broken as you expect to see a new message every few minutes - something is off.
Now compare this to a very slow-paced and small community. You know that, if you post something in your little, nifty chat room that you don't need to expect an answer for a few days. After a few days, your message is answered and to no time you felt as the basic liveliness is disrupted. However, in another case you didn't get an answer for a whole three weeks - now you will curious as nobody answers you. The basic liveliness is disrupted.
So the term boils down to the "standard" time of receiving a message in a particular community or chat room. It's nothing fixed, rather relative and is a good measure for users to expect answers.