FILL THE BLANK. Jayshawn is conducting a research experiment for his psychology course. He is studying whether playing violent video games causes acts of violence in children. He decides to give one group a violent video game and another group of children no video game at all. In the hour to follow, he will measure their tendency to be violent in the presence of a bo-bo doll. In this experiment, whether or not the children are exposed to violent video games functions as the _______.