This classroom activity offers a vivid and memorable way to demonstrate an important lesson from recent research on the psychology of happiness: that spending money on others often leads to greater happiness than spending money on oneself. Indeed, even the act of reflecting on a prosocial spending leads to greater happiness than thinking about spending the same amount of money on oneself. To illustrate this finding, the instructor gives students one of two handouts: a blue sheet that asks students to describe the last time they spent approximately $20 on themselves, or a yellow sheet that asks them to describe the last time they spent the same amount on someone else. In both cases, the sheet ends by asking students to rate their current happiness on a 9-point scale. Then, once students have completed the writing assignment and rating, they're asked to crumple the sheet into a ball and throw it at one of three signs in the front of the classroom corresponding to the rating they gave: 1-3 (a relatively low level of happiness), 4-6 (medium happiness), or 7-9 (high happiness). The most common result is that the 7-9 sign draws more yellow balls than blue balls, which sets up a discussion of how helping others can, in turn, help oneself.