Can we ‘catch’ emotions from others? Elaine Hatfield, author of the acclaimed book Emotional Contagion, first published in 1994, said yes — and many others have come to agree. The rise of social media since 1994 makes this work even more useful today.

Recent research has focused on emotional contagion through social media. Facebook users exposed to newsfeeds with fewer negative words made fewer negative posts themselves, and those exposed to fewer positive words made fewer positive posts. Similarly, a study of YouTube viewers who watched positive videos experienced more positive emotions; the same held true for negative posts. Important learning, I’d say.

Though the book can be somewhat dense and technical, it’s worth having on your shelf as a reference, if not to read cover to cover.