There are two types of flashcards, physical and digital. As for which type is better, there is evidence that goes both ways. However, a recent study (Dizon and Tang, 2017) found that both are essentially equally effective if students have been taught how to use them. For teachers, I think we are fine to use whatever type works better for our context. Don’t stress about which form to use, just make sure you teach your students how to use them.
Flashcards are effective because they force students to use the study strategy of retrieval practice. When applying retrieval practice to a flashcard, students read the cue (question) and then they must retrieve, from memory, the information (answer). Then students look at the other side of the card and get feedback on whether they were correct or not. Each time a student retrieves the information correctly, they are reconstructing the memory of that fact/concept. This reconstruction makes it easier for students to recall the relevant fact/concept in the future.
The formatting of flashcards also lends itself to spaced repetition. Spaced repetition is exactly what it sounds like, spacing the repetition of the material out. The meaning and impact of spaced repetition becomes more clear when contrasted with cramming, its opposite. Cramming can be somewhat effective at improving student performance, but it doesn’t help much for actual learning as most of what a student crams will be forgotten shortly after the test (Bjork, 2012). Spaced repetition helps with both test performance and actual learning.
Now for some hard data. Flashcards have been shown to improve student performance on tests. A study found that students who used flashcards to study for every test in an “Intro To Psyc” class much better than those who did not use flashcards (Golding, Wasarhaley, & Fletcher, 2012). Another reason that teachers should use flashcards is that subject-specific vocabulary is the strongest predictor of student performance on content-based assessments (Espin and Deno, 1995). A study done by Nate Kornell looked at flashcards and test scores found that for 90% of students, spacing out their practice was more effective than cramming (Kornell, 2011). The same Kornell study found that students who used a spaced repetition flashcard strategy scored over 30% higher than students who used a massing flashcard strategy. In this case, the massing strategy involved using a small deck of flashcards on specific topics (lessons), whereas the spaced repetition strategy used a large set of flashcards that included information for the whole chapter. This provides evidence that flashcards are more effective when they utilize the interleaving study strategy.
As teachers, we care about test performance (It is important!) but actual learning (putting information into long-term memory) matters more. I believe that the above information gives strong evidence for utilizing retrieval practice, spaced repetition, and interleaving as study/teaching strategies. I also think that flashcards can be a way to integrate these study strategies into a simple, effective, and student-friendly form.