Background/Need: Easy-to-implement pedagogical strategies that can improve performance in STEM barrier courses are needed to increase the pool of students capable of graduating with STEM degrees and ultimately working in STEM fields. One such strategy is spaced retrieval practice, a memory-enhancing instructional technique in which multiple questions about the same topic are administered over time, with delays in-between. Traditionally, undergraduate STEM classroom practices have encouraged massed retrieval, whereby all questions on the same topic are asked in a short span of time (e.g., on a quiz or homework administered at the end of a unit). This study (NSF IUSE 1912253) builds on two previous NSF IUSE grants 1431544, 1609290. This study implemented spaced retrieval practice and assessed its impact in nine STEM courses in six domains at the University of Louisville: mathematics, physics, chemistry, biology, psychology, and engineering. The two previous studies examined the effect of spaced retrieval practice in a precalculus course for engineering students. Results showed that spacing improved performance in a precalculus course by 3-5%, or a third to a half a letter grade, with even larger effects on long-term retention.
Guiding Questions and Study Design: Research questions in this study were: 1. Does spaced retrieval practice (versus massed) increase retention of objective-specific knowledge in a variety of STEM barrier courses? 2. Is spaced retrieval practice ineffective in any courses? 3. In those courses in which spaced retrieval practice leads to greater retention than massed retrieval practice, does the magnitude of the spacing-related benefit differ? The manipulation was within-subjects and identical in all nine courses. For each of 24 learning objectives, three quiz questions were either spaced across three quizzes over five weeks or massed on a single quiz. Retention was assessed on a test at the end of the semester.
Outcomes: Results in this comprehensive study found the effect of spacing differed across courses, ranging from robust spacing-induced gains to no discernible effect. Clear-cut evidence of a spacing effect was obtained only in calculus. The magnitude of the effect was similar to effects in the pre-calculus studies. We also found evidence that the positive effect in calculus is robust across different subpopulations of students. In other classes spacing produced either modest non-significant gains or had no discernible effect.
This study confirms the positive effect of spacing for mathematics undergraduate education but indicates that generalizability of the spaced retrieval benefit across STEM domains is elusive. These results support the adoption of a viable educational strategy to increase student success in mathematics courses nationwide. Increasing student success in mathematics courses should support STEM education broadly, and support conferment of more STEM degrees and increase the number of individuals who successfully pursue STEM careers. Moreover, innovations that improve STEM teaching should especially benefit students who traditionally underperform in STEM, including students from underrepresented groups.
Patricia Ralston, University of Louisville; Keith Lyle, Louisville, Ky; Jason Immekus, University of Louisville