Cats yawn because they realize that there's nothing to do. 猫打呵欠因为它们认识到无事可做。
The researchers found that those who breathed through the nose rather than the mouth were less likely to yawn when watching a video of other people yawning. 研究人员发现，在看别人打呵欠的视频时，用鼻子呼吸的人比用口腔呼吸的人打呵欠的几率要小。
