Most of the participants in the experiment were students. They were taken to a lab and their faces were painted with black lines, in order to study the movements of their facial muscles. They were then exposed to a variety of stimuli designed to create a strong reaction. As each person reacted, they were photographed by Landis. The subjects were made to smell ammonia, to look at pornography, and to put their hands into a bucket of frogs. But the controversy around this study was the final part of the test.