The psychological effects of yerba mate are myriad and continually being discovered. The main effect is mate’s ability to naturally increase alterness and concentration. Also, the idea of “creative clarity”, where mater drinkers experience a sense of heightened creative energy. Here are a few articles to explore: The Psychological Effects of Yerba Mate, Yerba Mate Improves Ability to Read, Building a Relationship with Yerba Mate.