Spacing your practice really works
An often-heard criticism of research on things like spaced practice, retrieval practice, interleaving and so further is that they are primarily lab studies with little ecological validity (does it work in real life?). Here’s a study by Marissa Hartwig and Eric Malain where the results show that spacing in a naturalistic (i.e., ecologically valid) situation.
We examined students’ naturalistic decisions about spacing their study in an undergraduate course (N = 185) and whether self-selected spacing predicted course performance. Usage of two study tools – an online textbook and quiz tool – was recorded daily. We operationalized spacing as how often the tools were used and the timing of their use relative to exams. We found that students increased their study near deadlines and exams, used the textbook more often than the quiz tool, and used the tools infrequently when they were optional (vs. required). Importantly, spaced retrieval practice (via quiz tool) predicted course performance and GPA, whereas spaced reading (via textbook) was a weaker predictor. That is, when students opted for more frequent and early quizzing, they earned higher grades, even controlling for time spent quizzing. Thus, self-selected spaced study – especially spaced retrieval practice – supports student achievement.
The present research suggests that self-selected spaced study (especially when involving retrieval practice) is consequential for real-world student performance. It also highlights the key role that instructors can play in encouraging beneficial study behaviors. Here, we saw that course structure, deadlines, and incentives influenced students’ study behavior. To promote long-term retention of important material, instructors could incentivize spacing of retrieval practice across the duration of a course. For example, frequent low-stakes quizzing is one way for teachers to promote spaced retrieval practice in their classrooms. Alternatively, students could earn points for completing practice quizzes multiple times before an exam. Perhaps, to earn full credit, students might be required to quiz themselves on three separate days and begin at least two weeks before an exam. While students can sometimes benefit from controlling their own study (e.g., Tullis et al., 2018), students also frequently make bad study decisions, such as waiting to study until an exam approaches or not taking advantage of study tools offered to them. By using low-stakes incentives – minimal points per study session which accumulate to be meaningful towards the course grade – instructors can shape study behavior without removing student autonomy.
 Ecological validity refers to the realism with which a design of evaluation setup matches the user’s real work context. It is about how accurately the design or evaluation reflects the relevant characteristics of the ecology of interaction, i.e., its context in the world or its environment. (https://www.sciencedirect.com/topics/computer-science/ecological-validity)