The U.S. Marine Corps training and education enterprise is undertaking a modernization effort to improve student Marine learning outcomes and information retention. Adaptive flashcards that are tailored to an individual learner’s needs present a promising technique to promote learning and retention by employing optimal study strategies that maximize the benefits flashcards can provide. Using desirable difficulty as a theoretical framework, the present experiment compared two novel adaptive flashcard training algorithms that varied the difficulty of each flashcard by manipulating the number of response options. Although both algorithms considered item correctness, one condition adapted the number of response options based on participants’ reaction time (RT condition) and another adapted based on participants’ appraisals of mental effort (ME condition). These two adaptive conditions were compared to a non-adaptive control condition that did not change the number of response options. Ninety-six participants completed digital flashcards in one of the three experimental conditions. After training, participants completed an immediate post-test and returned one week later to complete a delayed post-test. Overall, the results suggest the adaptive approaches resulted in higher immediate post-test performance compared to the control condition. However, we did not uncover specific advantages for using either RT or ME algorithm. Additional mediation analyses indicated adapting difficulty impacts in-training performance, which can subsequently affect test performance. Overall, the results from this experiment highlight the potential of novel approaches to flashcard-based training for improving learning outcomes and information retention in USMC schoolhouses through modern, learning-centered adaptive training techniques.