Facebook manipulated 689,003 users' News Feeds to 'prove' emotions are contagious
If you are exposed to negative person, then that negativity might bleed over to infect you. If you are exposed to a positive person, then those positive emotions might put you in a more positive frame of mind as well. Since you likely have experienced that in real life, then you probably don't need research to back that up. Facebook's data scientists were out to prove if emotions expressed digitally would also be contagious.