Information Cascade Before Our Class Today

From Wikipedia: "An information (or informational) cascade occurs when people observe the actions of others and then make the same choice that the others have made, independently of their own private information signals. Because it is usually sensible to do what other people are doing, the phenomenon is assumed to be the result of rational choice. Nevertheless, information cascades can sometimes lead to arbitrary or even erroneous decisions."

When I got to class today (right after our TAs and professors), we saw a bunch of people just sitting outside the classroom. There were signs up about some seminar/talk, so we assumed that they had already checked inside and had found that the talk was still in session. The rest of us assumed they were right and waited outside as well. We were wrong.

Someone came out of the room and asked, "Why are you guys all out here? There are two guys in there, but they're just waiting for class to start."

He broke our fragile cascade.

My question is, who was the first person that sat down without checking? You started the information cascade.

...that I was part of the cascade. I was third to get there. When I got there, I saw two people sitting outside. So I asked them if there was a class in there, they confirmed and so I sat down outside as well.