We set our parameters pretty carefully: We would time those who were watching this exhibit, from the time they started looking at the exhibit until they looked away and paid attention to something else. If they looked back, we'd restart the clock. If there was a group going through the museum together, we'd continue as long as some member of the same apparent group was watching the exhibit. Once we were done, we would approach people and let them know their time, and offer them the brochure.