I laughed when I saw 2 people on this thread say it has been "scientifically proven" that it is. That is a load of bull. It has NOT been proven. At the very most, 2 things have been concluded. There is a subconscious reaction to being aware of another yawn, and the average person takes about the same amount of time to yawn in specific conditions. Allow me to explain both.

First, yawns have a tendency to happen when the thought enters your mind. Seeing someone yawn or hearing/reading the word yawn puts that in your mind, triggering the response. But a response triggered by your own mind does not mean contagious. Contagious means it is something that you can catch specifically from another host. A yawn is just something that happens because of your own body/mind. It is not someone's yawn jumping to you. Therefore, not contagious.

Now for the other part. One test was done where many groups of people were gathered. Each thought they were doing in for things like surveys, poll tests, etc. They were not told what the study was for. They each were put in cubicle sized rooms, all next to each other with a hidden camera. The idea is if they were all close to each other without knowing there were others close to them, they could try to determine if others could catch another one's yawn. They told the people someone would be there soon, and they never sent anyone in. They all pretty much were put in a waiting game. When one person yawned, they did notice a chain reaction where everyone started yawning quickly after. But that doesn't mean anyone caught the original yawn, so they tried another setup. Using more test groups, they put people in small rooms with hidden cameras, but the rooms were in no way close to each other. Many were in different floors, many in different buildings, and many not even on the same block. They noticed through hidden camera that one person eventually yawned, and everyone else quickly followed. When none of them were even in close proximity, one thing was determined. When you have many people in the same situation, most people will take somewhere around the same amount of time to yawn. Many more groups were put in various situations/environments, and this idea was supported. So again, not contagious.

Those who say they yawned behind someone and that person then yawned, that may be true. But that doesn't mean contagious. When they are in the same room as you, they are being exposed to the same condition/environment, so you are seeing the natural phenomenon that people tend take the same amount of time to start yawning in the same situations.

So to sum it up, it is not contagious. It is a subconscious reaction and a timed event. It isn't something you literally catch.