Contagious yawning may show the closeness of your relationships rather than your tiredness, say scientists.
The fact that it is contagious has never been fully explained, but one theory suggests it is linked to empathy between people. An Italian study in the journal PLoS One found people were more likely to yawn in response to a close relative rather than just a friend. The finding suggests contagious yawning may have evolved as a way of maintaining alertness within a group.(BBC News)