It's a well-known fact that yawning is contagious and can spread around a room in a matter of seconds, but it turns out the phenomenon is more common among women. 众所周知，打哈欠是会传染的，一个房间里的人陆续打哈欠，也就是...
Almost all animals with a spine yawn.Penguins do it as a mating ritual,snakes do it to realign their jaws after a meal and guinea pigs do it to display anger,So why exactly do humans yawn?And is yawning actually contagious? 几乎所有的有脊椎动物...
