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What’s the Perfect Number of Friends for a Night Out?

You don’t want to be the third wheel (or the fifth)

Short answer: It’s four.

But wait: Let’s examine this a little further. To start with, let’s compare two of the most significant groups in the history of human achievement: The Beatles and the Three Stooges. The Beatles — not coincidentally, also known as the “Fab Four” — revolutionized rock music while also influencing culture, politics and society as a whole. As for the Stooges, consider the film, Disorder in the Court, in which a courtroom erupts into mayhem because Curly gets his head stuck in a letterpress and Larry mistakes a man’s bow tie for a tarantula.

Ah, but didn’t The Beatles break up, you’re thinking? Well, yes. Now you’re thinking: Yeah, but I can think of plenty of harmonious threesomes (the Three Musketeers!) as well as troubled foursomes (Metallica). So, no, the analogy isn’t perfect. Or really scientific in any way. But despite this ill-conceived comparison, the correct number of friends for a night out is still four, and there’s a good deal of scientific reasoning behind it.

“A group of four is as many good friends as you can manage,” says the renowned British anthropologist and evolutionary psychologist Robin Dunbar. He adds that this is “also the limit for conversation group size as well as laughter group size.”

For conversation group size, it helps first to understand something called “Theory of Mind,” which is really the key component in one’s ability to understand others, explains Frank McAndrew, a professor of psychology at Knox College. It essentially means that, during conversation, a participant understands that the person with whom they’re communicating may have different intentions, as well as a different state of mind, than their own. This allows us to see the emotions of other people and allows us to process empathy. It also permits our brains to understand that people have different political or social beliefs than our own. It’s the basic principle that lets us understand not just other people’s opinions, but that other opinions exist at all — that not everyone thinks and feels like we do at all times. Really, it’s the key to being able to manage human relationships at all.

Theory of mind has limitations, though. Once we reach four people — or five at the very most — our ability to understand breaks down, as we simply don’t have the mental capacity to process more than that. Because of this, McAndrew explains, “If you get any larger than five, the group would start splitting up into smaller sub-groups, which may start heading off in their own directions.” This will probably happen literally, too: More than five people will likely end with no one being able to agree on anything, preventing any kind of consensus as to what the group should do and maybe see people heading off to different bars.

While five might be able to work, four would probably still be better due to other, more tangible constraints. A typical Uber will only seat four before you have to upgrade to an XL. Table size may also play a factor, as the typical table at a restaurant will only seat four. McAndrew further explains, “Although side-by-side seating connotes intimacy [like you and your buddies crammed side-by-side at a bar], it doesn’t seem to be the preferred arrangement for talking.” He continues that, predictably enough, studies have shown that conversation is more productive when you’re actually facing those you’re talking to.

The other limiting factor is what Dunbar refers to as “laughter group size.” “Laughter plays an important role in human bonding,” Dunbar explains — through laughter, we make friendships and lasting relationships. But it has some constraints: While laughter may bond people, it does a much more effective job of bonding people in groups of four or less. While Dunbar says that part of this may be due to acoustic constraints — i.e., it helps to hear a joke to laugh at it — another reason may be that the intimacy of laughter as a means of conversation also helps to confine it to smaller groups.

Why, then, can a stand-up comedian entertain a group of hundreds? Well, in these situations, “We think we’re in a small virtual group with the comedian and the people immediately with us, which might explain why not everyone laughs at the same time in a club or theater,” Dunbar previously told NBC news.

So while theory of mind, conversation group size and laughter group size may explain why four is about the maximum group size you’d want for a fun night out, why wouldn’t three be just as good, or perhaps even more intimate in their bonding? McAndrew explains, “Three-person groups are notoriously unstable.” This is because, “It’s easy for two people to form a coalition to make the third person feel marginalized.” So, if you’re going out in a group of three, more than likely, two of you may be just a little bit closer than the third person — as a result, that third person will likely become marginalized. McAndrew adds, “You greatly enhance the possibility that you end up with a disgruntled individual being dragged around by two other people.”

A fine example of this marginalization is in the Three Stooges short, “A Plumbing We Will Go,” where the boys are hired as plumbers. In it, Larry ends up branching off from the others to dig up the front lawn while Moe and Curly end up connecting a water pipe with electrical wires. Needless to say, the polarization of Larry leads to disaster for everyone, especially the person who hired them in the first place.

See, that analogy wasn’t so bad after all, was it?