There are multiple theories as to why people yawn in response to seeing others yawn. One theory is that contagious yawning is a result of the power of suggestibility. Another theory revolves around the idea that contagious yawning is related to human beings' predisposition toward empathy.
There is a demonstrated link between yawning and empathy, the ability to understand the emotional states of others. Researchers at Leeds University in England showed that people whose profession requires them to be more empathetic and focus more on others, such as psychologists, tended to yawn more than people whose profession required them to focus on numbers and systems, such as engineers, when placed in a room for 10 minutes with another individual who yawned as many as 10 times during the experiment. It was also shown through neural imaging that the same parts of the brain that deal with empathy also regulate the yawning response in humans.
Empathy is an important part of human psychological development. The empathy that parents show to their children influences a child's level of self esteem and the empathy that people are able to develop later on in life influences how successful they are in navigating social relationships.