字幕列表 影片播放 列印英文字幕 We've all heard that yawning is contagious, so how long are you able to last while watching this video? Once you've yawned, click here on the screen, or use the link in the description below to see our video explaining why we yawn in the first place and why it's contagious. Still here? There might actually be a reason why you didn't yawn at all. Make sure you watch our other video, here, to find our why.