<p>Flash cards work for two main reasons:</p>

<ol>
<li>they serve as retrieval practice</li>
<li>they force the student to space practice out</li>
</ol>

<p>Both of these reasons have been demonstrated to enhance learning.</p>

<p>Retrieval practice, sometimes called the <a href="http://en.wikipedia.org/wiki/Testing_effect"><em>testing effect</em></a>, has been shown by <a href="http://psych.wustl.edu/memory/">Roediger and colleagues</a> to promote learning above and beyond additional study. For instance, <a href="http://psych.wustl.edu/memory/Roddy%20article%20PDF%27s/Roediger&amp;Karpicke%282006%29Psych_Sci.pdf">in a 2006 study by Roediger and Karpicke</a>, some subjects studied material several times then took a test (SSST, where S = study and T = test), whereas other subjects studied material less then took a several tests (STTT). After a brief delay, memory was shown to be better for those who had self-tested relative to those who hadn't. <a href="http://psych.wustl.edu/memory/Roddy%20article%20PDF%27s/Karpicke_Roediger_2007_JML.pdf">In a 2007 study by Karpicke and Roediger</a> that actually used flash cards, the memorial benefit was always greater when individuals self-tested rather than merely restudied -- and importantly, best when individuals continued to self-test even when they thought they had the information down cold. This suggests that you shouldn't "drop out" flash cards from the deck if you get them right once or twice. <a href="http://psych.wustl.edu/memory/Roddy%20article%20PDF%27s/Roediger%20&amp;%20Karpicke%20%282006%29%20Review.pdf">Another 2006 Roediger and Karpicke paper</a> provides additional evidence in more applied contexts.</p>

<p>The spacing effect is also a powerful influence, here, as well. <a href="http://bjorklab.psych.ucla.edu/index.html">Research by Bjork and colleagues</a> on a parsimonious (yet slightly circular) idea called <em>desirable difficulties</em> provides one theoretical example for why this is so. Learning is most powerful when it is most difficult, and spacing out your study (or, as above, your test) provides that information with time to decay (or be interfered with by other memories) such that when retrieval is successful, it is rather potent. Note that one concern with spacing is that if study is pushed too far out, successful retrieval cannot occur, leading to no benefit to memory.</p>

CC BY-SA 3.0
2012-02-23T13:17:49.423Z
Any thoughts on whether the SuperMemo algorithm has any evidence behind it, besides the author's own experience?
Chris S
CC BY-SA 3.0
2012-02-24T03:53:50.560Z
Very important point about not "dropping out" cards after a small number of correct recalls
Zelda
CC BY-SA 3.0
2014-07-22T07:00:38.833Z
@ChrisS: finally someone asking about evidence.. Fortunately there is some: http://www.supermemo.com/english/princip.htm#spacing_effect
LetMeSOThat4U
CC BY-SA 3.0
2012-02-23T05:19:26.067Z
2012-02-23T15:13:24.507Z
2012-02-23T15:13:24.507Z
Andy DeSoto
<p>There's lots of research out there on flash cards and they are a proven, effective study aid.</p>

<p>Flash Cards work because of the "<a href="http://en.wikipedia.org/wiki/Forgetting_curve">Forgetting Curve</a>"; rehearsal and retrieval before you forget an item strengthens the memory before it decays allowing one to optimize encoding into LTM.</p>

<p><img src="https://i.sstatic.net/lKZuc.png" alt="enter image description here"></p>

<p>The paper <a href="http://onlinelibrary.wiley.com/doi/10.1002/acp.1537/abstract">Optimising learning using flashcards: Spacing is more effective than cramming</a> is a good summary of why Spacing helps retention, highlighting why it's effective in education and should be emphasized over cramming, which current educational models (finals, tests) currently promote.</p>

<p><a href="http://en.wikipedia.org/wiki/Spacing_effect">Spacing</a> is effective for <strong>Long Term Memory</strong> as opposed to <a href="http://en.wikipedia.org/wiki/Cramming_%28memorization%29">cramming/massing</a> which is only effective (but it IS effective) in the short term as shown by the above forgetting function.</p>

CC BY-SA 3.0
2012-02-23T05:20:34.537Z
Nice answer. I like the statement that "rehearsal and retrieval before you forget an item strengthens the memory" and expand a little bit on this in my answer, though. There are interesting reasons why we might not want to talk about "memory strength," however, which is a discussion for another day!
Andy DeSoto
CC BY-SA 3.0
2012-02-24T19:44:20.370Z
I haven't seen the forgetting curve before but it matches the Supermemo algorithm almost exactly. Having read http://www.amazon.co.uk/Your-Memory-How-Works-Improve/dp/1569246297/ref=sr_1_5?ie=UTF8&qid=1330112466&sr=8-5 active recall seems to be quite a common theme/proven theory in learning.
Chris S
CC BY-SA 3.0
2012-02-22T19:27:46.743Z
2012-02-22T19:27:46.743Z
Zelda
<p>Several apps and sites offer flashcard-based learning that repeat the cards you do poorly on over a period of time (the more inaccurate the answer the closer to each other the repetitions are). One example of this is <a href="http://www.supermemo.com/english/smintro.htm">Super Memo</a>.</p>

<ul>
<li>Is there rigorous empirical support for these types of flashcard systems working?</li>
<li>Do they exploit a known function of memory?</li>
</ul>

CC BY-SA 4.0
2024-09-12T03:49:26.267Z
Also see: [Evidence of flattening forgetting curves with spaced repetition and formulas to predict them](https://psychology.stackexchange.com/q/30575/7001)
Arnon Weinberg
<learning><memory><mnemonic><encoding>
Are spaced flashcards effective for learning?
Chris S
# Are spaced flashcards effective for learning?

(Asked by: username_0 on 2012-02-22)

Several apps and sites offer flashcard-based learning that repeat the cards you do poorly on over a period of time (the more inaccurate the answer the closer to each other the repetitions are). One example of this is [Super Memo](http://www.supermemo.com/english/smintro.htm).

* Is there rigorous empirical support for these types of flashcard systems working?
* Do they exploit a known function of memory?

**Tags:** learning, memory, mnemonic, encoding

> **Comments:**
> **username_1**: Also see: [Evidence of flattening forgetting curves with spaced repetition and formulas to predict them](https://psychology.stackexchange.com/q/30575/7001)  

---

## 2 answers

### Answer by username_3 on 2012-02-22. Score: 19 | Accepted answer

There's lots of research out there on flash cards and they are a proven, effective study aid.

Flash Cards work because of the "[Forgetting Curve](http://en.wikipedia.org/wiki/Forgetting_curve)"; rehearsal and retrieval before you forget an item strengthens the memory before it decays allowing one to optimize encoding into LTM.

![enter image description here](https://i.sstatic.net/lKZuc.png)

The paper [Optimising learning using flashcards: Spacing is more effective than cramming](http://onlinelibrary.wiley.com/doi/10.1002/acp.1537/abstract) is a good summary of why Spacing helps retention, highlighting why it's effective in education and should be emphasized over cramming, which current educational models (finals, tests) currently promote.

[Spacing](http://en.wikipedia.org/wiki/Spacing_effect) is effective for **Long Term Memory** as opposed to [cramming/massing](http://en.wikipedia.org/wiki/Cramming_%28memorization%29) which is only effective (but it IS effective) in the short term as shown by the above forgetting function.

> **Comments:**
> **username_2**: Nice answer. I like the statement that "rehearsal and retrieval before you forget an item strengthens the memory" and expand a little bit on this in my answer, though. There are interesting reasons why we might not want to talk about "memory strength," however, which is a discussion for another day!  
> **username_0**: I haven't seen the forgetting curve before but it matches the Supermemo algorithm almost exactly. Having read http://www.amazon.co.uk/Your-Memory-How-Works-Improve/dp/1569246297/ref=sr_1_5?ie=UTF8&qid=1330112466&sr=8-5 active recall seems to be quite a common theme/proven theory in learning.  

---

### Answer by username_2 on 2012-02-23. Score: 16

Flash cards work for two main reasons:

1. they serve as retrieval practice
2. they force the student to space practice out

Both of these reasons have been demonstrated to enhance learning.

Retrieval practice, sometimes called the [*testing effect*](http://en.wikipedia.org/wiki/Testing_effect), has been shown by [Roediger and colleagues](http://psych.wustl.edu/memory/) to promote learning above and beyond additional study. For instance, [in a 2006 study by Roediger and Karpicke](http://psych.wustl.edu/memory/Roddy%20article%20PDF%27s/Roediger&Karpicke%282006%29Psych_Sci.pdf), some subjects studied material several times then took a test (SSST, where S = study and T = test), whereas other subjects studied material less then took a several tests (STTT). After a brief delay, memory was shown to be better for those who had self-tested relative to those who hadn't. [In a 2007 study by Karpicke and Roediger](http://psych.wustl.edu/memory/Roddy%20article%20PDF%27s/Karpicke_Roediger_2007_JML.pdf) that actually used flash cards, the memorial benefit was always greater when individuals self-tested rather than merely restudied -- and importantly, best when individuals continued to self-test even when they thought they had the information down cold. This suggests that you shouldn't "drop out" flash cards from the deck if you get them right once or twice. [Another 2006 Roediger and Karpicke paper](http://psych.wustl.edu/memory/Roddy%20article%20PDF%27s/Roediger%20&%20Karpicke%20%282006%29%20Review.pdf) provides additional evidence in more applied contexts.

The spacing effect is also a powerful influence, here, as well. [Research by Bjork and colleagues](http://bjorklab.psych.ucla.edu/index.html) on a parsimonious (yet slightly circular) idea called *desirable difficulties* provides one theoretical example for why this is so. Learning is most powerful when it is most difficult, and spacing out your study (or, as above, your test) provides that information with time to decay (or be interfered with by other memories) such that when retrieval is successful, it is rather potent. Note that one concern with spacing is that if study is pushed too far out, successful retrieval cannot occur, leading to no benefit to memory.

> **Comments:**
> **username_0**: Any thoughts on whether the SuperMemo algorithm has any evidence behind it, besides the author's own experience?  
> **username_3**: Very important point about not "dropping out" cards after a small number of correct recalls  
> **username_4**: @ChrisS: finally someone asking about evidence.. Fortunately there is some: http://www.supermemo.com/english/princip.htm#spacing_effect  

---

