Student response systems, or "clickers," have been presented as a way of solving student engagement problems, particularly in large-enrollment classes. These devices provide real-time feedback to instructors, allowing them to understand what students are thinking and how well they comprehend material. As clickers become more common, it is important to assess their impact on student learning and engagement. Utilizing individual-level data from introductory courses in political science, we demonstrate that students both approve of clicker usage and that they are positively associated with class performance. Using clickers to test students' understanding of class concepts has positive effects on exam and essay scores even after controlling for previous levels of academic achievement, students' evaluation of the technology, and other socioeconomic traits.