Yawning is contagious among humans, dogs and primates, but not tortoises. What makes tortoises different?
Yawning is very contagious in the human species. Some people will yawn just because they are reading about yawning! Every time you yawn and is observed by another person while you are doing it, 40-60% of the time that person will yawn too.
This is not only a human behavior. Dogs can ‘share’ yawns with each other and with humans, and so can primates. Yawning is a fixed action pattern, which means that it can not be stopped once it has started happening.
To discover whether yawning is an empathetic behavior, scientists had to test the theory using animals that live together socially, but don’t really have ‘feelings’ for other animals of their species. For this experiment, red-footed tortoises were ideal.
They trained one to yawn when it saw a red dot. This took six months to accomplish! They had other tortoises observe the trained tortoise to see if they respond to a yawn by also yawning. It did not matter how they approached the experiment, they got negative results. Tortoises really don’t care at all whether a fellow of their species yawns or not!
The results could mean that contagious social yawning requires a social sense or sense of empathy resulting from complex social interactions.