Text 1

It seems clear that emotional contagion (the unintentional transfer of an emotional state from one person to another) requires physical interaction and the observation of body language. After all, research shows that talking to someone who is smiling and expressing positive feelings often causes people to respond in a comparably positive way. Similarly, displays of nervous fidgeting have been found to prompt others to begin behaving more nervously, too.

Text 2

In an experiment using a social networking service, Zeyao Yang and Emilio Ferrara found evidence of emotional contagion in text-based online interactions. The researchers discovered that reading social media posts that expressed a positive outlook led people to make more positive posts themselves, while posts with a negative emotional tone led people to make more negative posts.