One of most difficult aspects of actually designing an experiment is to decide precisely what the participants should do. Once the participants are sitting in the experimental chamber staring at the stimuli, they have to actually perform some task, but which one? The possibilities are nearly endless. We might ask them to describe what they see in their own words. We might ask them to rate some specific aspect of what they see. We might even ask them to interact with the stimuli (e.g., driving a virtual car or flying a virtual plane). We might even forgo overt actions and measure how their brains, hearts, or sweat-glands respond to what they see.