In Lord of The Flies, in what ways did the boys act differently (because of being stranded on an island) compared to a more real-life situation?
I would say one immediate difference is the fact that the boys recognized early on that they need a system of governance in place. On the island, that sort of thing didn't exist. At home it does exist. The major difference is that at home, in "real life," the boys would not have taken an active role in self governance. The adult would have set forth a bunch of rules for the boys to obey. Now, they have to do it themselves.
“Shut up,” said Ralph absently. He lifted the conch. “Seems to me we ought to have a chief to decide things.”
Another simple, but major, difference is all of the killing that happens. Simon and Piggy are both killed. You could argue that Simon was an accident, but I don't think the boys would have been doing a ritualistic hyper dance fire party back at home that ended up killing someone. Piggy's death, on the other hand, was intentionally done by Roger. The boys also resorted to killing things like pigs. That was out of necessity for survival, but the need to do it and organize into hunting parties never would have crossed their minds in more "real life" situations.
I would like to provide a sort of counter point too. I would like to suggest that the characters' personalities probably didn't change that much on the island compared to being at home in civilization. I'm quite certain Jack has always been an alpha male who hates losing. I'm sure Roger has always been a jerk and enjoyed hurting people. Piggy and Simon, are great characters, but quite static, so I don't see them changing all that much. Roger was likely a well liked rule follower at home, too. What the island did to the boys though was take away any sort of adult oversight to control the boys' more beastly impulses. That's why Jack and Roger essentially turned their dials up to 11. There was no fear of punishment.