This accords with anecdotal evidence that people often yawn in situations where they are neither tired nor bored, but are preparing for impending mental and physical activity.
That may be a hint that yawn evolved as a social cue—"time for us all to go to bed".
也许这是打哈欠进化为社交线索的一种暗示——“到我们大家睡觉的时间了”。
3
Inspiration for her study came when she tried to get her own autistic son to clear his ears on an airplane. She repeatedly yawned at him, hoping he would yawn back.