The study reported in this paper involved the employment of specially designed learning activities based on the use of a Personal Response System (PRS). Instructors in variety of disciplines are increasingly using personal response systems to increase participation, engagement and active learning. Most studies stress the benefits of using a PRS when dealing with large groups; in this paper we stress learning benefits for small classes. We demonstrate in a context of two very different courses how the PRS use can foster formative interactions in class as well as focusing students on the main discipline-specific concepts and skills. We describe the characteristics of these two courses along with their educational goals and how it influenced the design of the PRS-based learning activities. We describe the formative interactions in class as triggered by the PRS-based questions, and we describe findings regarding students' perceptions of the various contributions of the PRS-based learning activities.