Clickers — or “personal response systems” (PRSs) — are rapidly becoming standard devices for eliciting real-time information about student comprehension during class. They work like this: the professor asks the students a question, in multiple choice format with a number assigned to each answer, and students give their answers by selecting the number on their PRS. The results are sent to a server, tallied, and then displayed on a screen in front of the class. The display format can be a bar graph, a pie chart, or any number of standard ways of displaying survey data. Professors have used these tools for a variety of ways, such as involving students into small groups to arrive at answers collaboratively.