“…Although extensive work has shown that retrieval practice can indeed aid retention (e.g., Carpenter et al, 2009;Carrier & Pashler, 1992;Dunlosky et al, 2013;Kang et al, 2013;Karpicke & Roediger, 2008;Pyc & Rawson, 2010;Roediger & Butler, 2011;Roediger & Karpicke, 2006a, 2006b, most of this literature is limited to direct memorization and does not typically involve true concept learning. Moreover, the limited work that has been conducted on this topic has yielded inconclusive results, as some of this work has shown a modest benefit of retrieval practice and testing on concept learning and transfer (Butler, 2010;Butler et al, 2017;Eglington & Kang, 2018;, but other studies have failed to replicate this finding (Peterson & Wissman, 2018;Tran, Rohrer, & Pashler, 2015;van Gog & Kester, 2012;Wissman, Zamary, & Rawson, 2018). It is therefore an empirical question as to whether these principles can be used to help people learn ecologically valid, complex concepts.…”