You are at a party, and you get bored. You say “This isn't doing it for me anymore. I'd rather be someplace else. I'd rather be home asleep. The people I wanted to talk to aren't here.” Whatever. The party fails to meet some threshold of interest. And then a really remarkable thing happens: You don't leave. You make a decision “I don't like this.” If you were in a bookstore and you said “I'm done,” you'd walk out. If you were in a coffee shop and said “This is boring,” you'd walk out.
You're sitting at a party, you decide “I don't like this; I don't want to be here.” And then you don't leave. That kind of social stickiness is what Bion is talking about.
And then, another really remarkable thing happens. Twenty minutes later, one person stands up and gets their coat, and what happens? Suddenly everyone is getting their coats on, all at the same time. Which means that everyone had decided that the party was not for them, and no one had done anything about it, until finally this triggering event let the air out of the group, and everyone kind of felt okay about leaving.
This effect is so steady it's sometimes called the paradox of groups.
“A Group Is Its Own Worst Enemy [1]”
Spring [2] and Wlofie [3] were supposed to join some friends canoeing in the swamp (that's what we have here in Florida, swamps). But then the person who proposed the canoeing trip in the first place had a family emergency and couldn't make it. That caused another member to drop out. Then a third piped in, saying he couldn't make it because he was still recovering from a cold, and that his wife was now sick. Wlofie dropped out because his wrist is acting up again (Carpal tunnel syndrome [4]) and because he wasn't going, Spring dropped out.
Pretty much in the span of a few hours, the entire trip just fell apart.
I find it interesting how that works.
[1] http://www.shirky.com/writings/group_enemy.html