You won't believe what happened to us the other day. We were sitting on the sidelines of the Wonderopolis soccer pitch, watching a team of goats play a team of sheep in a heated soccer match.

With that many legs wildly kicking at the ball, we knew that things could get interesting. We were right. It wasn't long before a goat collided with a sheep and went down with a bleat. The badger serving as the referee called a foul, which led the sheep on the sideline to start their usual “Baaaaad call!" chant.

The badger got upset and the fur really started to fly. Watching a bunch of goats and sheep arguing with a badger is kind of a funny sight…at least that's what the hyena thought. Of course, he's prone to laughter and it didn't take much to get him going.

Soon enough, the hyena's cackles got the other spectators laughing, too. Before long, every animal in sight, from alligators to zebras, were rolling on the ground, laughing so hard they had tears streaming down their faces. Some of them didn't even know why they were laughing!

Have you ever experienced something like that? No, we don't mean watching a goats v. sheep soccer match. We're talking about uncontrollable, contagious laughter that gets you laughing so hard you can't breathe.

If you come upon a group of people laughing, it's only natural to start laughing, too. It's almost like you can't help it…even if you have no clue what's so funny! That's the contagious nature of laughter.

Fits of uncontrollable giggling naturally seem to happen when a group of people witnesses or experiences something humorous. Laughing with others is fun and makes you feel good. Many people would agree that laughter really is the best medicine.

Sometimes, though, uncontrollable giggling fits — especially when nothing funny is happening — can be a sign of a serious medical issue that might require a doctor's attention. For example, uncontrollable giggling fits can be a symptom of a chronic anxiety or neurological disorder that should be treated by a professional.

If you see someone laughing and their laughter makes you start laughing, don't worry! That's perfectly natural. It happens to all of us from time to time. No one knows for sure why laughter is contagious like it often is, but it might have something to do with our natural human desire to be accepted as part of a group by others in a social setting.

Scientists believe that laughing is mostly unconscious. In other words, you don't choose to laugh in the same way you choose to say something.

Instead, you see something that strikes you as funny and your brain has you laughing before you can even think about it. That's why you sometimes might laugh at something that strikes you as funny, such as someone falling, before you realize that it might be rude to do so!

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Be sure to check out tomorrow’s Wonder of the Day before it’s going… going… gone!