http://www.scientificamerican.com/article/kindness-emotions-psychology/

Teasing is the art of playful provocation, of using our playful voices and bodies to provoke others to avoid inappropriate behaviors. Marc Bekoff, a biologist at the University of Colorado, Boulder, has found in remarkable work with coyotes that they sort out leaders from aggressive types in their rough-and-tumble biting. The coyotes that bite too hard in such provocative play are relegated to low status positions. We likewise accomplish so much with the right kind of teasing.
Teasing (in the right way, which is what most people do) offers so much. It is a way to play and express affection. It is a way of negotiating conflicts at work and in the family. Teasing exchanges teach children how to use their voices in innumerable ways—such an important medium of communication. In teasing, children learn boundaries between harm and play. And children learn empathy in teasing, and how to appreciate others’ feelings (for example, in going too far). And in teasing we have fun. All of this benefit is accomplished in this remarkable modality of play.