The effects across studies show that:
- a previous question increases short-term and long-term exam performance on the repeated questions
- questioning distributed over 3 to 4 weeks of instruction increases long-term exam performance on both the repeated questions and novel related questions. The increase in performance is significantly greater after two or more prior presentations of the question.
- varied questioning increases generalization to a related question
- distributed questioning with multiple-choice questions increases exam performance on related short-answer questions
The authors explain that a couple of theories have been proposed to explain these findings. The first, based on a dual-system mammalian memory, suggests that "the memory system is designed to forget idiosyncratic events but retain routine events. Consequently, the distributed repetition of the question is assumed to be a causal feature of its long-term retention." The second theory posits that "social activity stimulated by clicker responses is more memorable than passive listening and solitary writing. [...] In addition, the social activity is supposed to raise the memorability of the entire lesson, not just the memorability of the questions and their answers."
Glass and Sinha conclude that "we are at the very beginning of an era in which surprising new findings will transform our understanding of how students learn."