This paper provides a theoretical framework for "reflection amplifiers" that are used in online courses. Such reflection amplifiers are intervention techniques that aim at provoking reflective practices in learning, in order to enhance the quality and effectiveness of learning and promote meta-cognition. A literature survey identified a sample of 35 different techniques, revealing a great variety of reflection amplifiers in today's educational practice. For the support of research into this topic, the paper provides a theoretical classification framework structured along two relevant attributes of reflection amplifiers: (a) the type of interaction which enacts the reflection amplifiers, and (b) the educational objective of the reflective activities. The framework provides a concrete and ordered expression of pursued reflective or meta-learning approaches. It has been used to create a mapping of the 35 identified techniques, enabling their detailed positioning, qualification and comparison. The framework also helps guiding future research activities and to create awareness among online course developers about the different approaches available. The paper concludes with the identification of relevant research challenges associated with the topic. (Contains 3 figures and 3 tables.)