This research presents the results of a study of alternative response methods for in class formative questioning. Students' anonymity from their peers and instructor was studied through a research design that maintained a constant interactive teaching strategy in a large lecture hall, in all respects except for the method used by students to respond to the in class questions. A handheld electronic response keypad was the only approach affording complete anonymity. Student perceptions of the benefits of anonymity were obtained from a survey conducted at the end of the course. The results suggest that anonymity is a critical factor affecting student willingness to participate with in class exercises. Furthermore, the results indicate that students' propensity to engage with in class questions increases with the degree of anonymity provided to the student in revealing their response. The benefit of anonymity, combined with the increased availability and affordability of electronic response systems, will be of interest to academics keen to design engaging learning environments. (Contains 2 figures and 4 tables.)