Background SlimStampen

SlimStampen: How it Works and Why

Decades of learning and memory research tell us that testing yourself is one of the most effective ways of learning. For the most effective self-testing sessions, you want to space out the items you’ re practicing. SlimStampen estimates the optimal way to space out the items based on the correctness and response time of your answers. Studies have shown that students who have studied with SlimStampen score 10 to 20% higher (Van Rijn et al., 2009; Wilschut et al., 2021). If you want to know more about this program, keep reading!    

The principles

SlimStampen is based on research in the field of learning and memory. Decades of this research has found two reliable effects: the testing effect and the spacing effect.

The testing effect

The testing effect is the finding that testing yourself is one of the most effective ways of learning. Testing yourself has been found to be more effective than reading and note-taking, for example (Rummer et al., 2017). When you successfully recall an item from memory, your memory for that item actually becomes stronger (Roediger & Karpicke, 2006). Practicing to recall an item during studying will also make it easier to recall that item on a test.   

A popular method of testing yourself has always been through written or printed flashcards. Nowadays, many students use digital learning programs like SlimStampen to practice retrieving words or facts from memory. The program will present you with items from a list that you want to study, one by one. For the first presentation, you will see both the question or cue and the answer, all following presentations you will only see the question or cue, and you will have to type the answer yourself (see Figure 1).

Figure 1. An example of studying foreign language vocabulary in SlimStampen.

The spacing effect   

The spacing effect is the finding that you learn better when you space out your study sessions. You have probably heard your teachers advise against cramming for exams a few days before (and you may have done it anyway). In the short term, cramming can work out, which makes it a tempting strategy. However, if you want to be sure that you will remember what you learned or if you want to remember what you learned for a longer time, your teachers were right: leaving some space (or, what we actually mean: time) between your study sessions is the way to go (Cepeda et al., 2006). 

Figure 2a. The spacing effect means that learning frequently in shorter sessions is more effective than learning in fewer, longer sessions.

Interestingly, this effect also applies to spacing of items within a study session (Van Rijn et al., 2009). You learn items better when you space them out in time instead of cramming them one by one (Figure 2b). Learning is more effective when you leave some time between repetitions of the same item. In that time, you can practice other items. However, if you wait too long to practice a certain item and you forget it, you have to start over. That is, of course, not very effective. To get the best learning gains, you’ll want to practice retrieving an item from memory at a moment in time where it is not yet forgotten, but it takes effort for you to retrieve it. The aim of SlimStampen is specifically to achieve this. The program estimates which item you are closest to forgetting and will present that item to you next.  

Figure 2b. The spacing effect also applies to facts within a study session. Spacing out the repetitions of a fact is more effective than cramming facts one by one.   

Putting science into practice   

Estimating which item a learner will forget first is not simple. After all, not everyone will forget an item after the same amount of time. How quickly items are forgotten differs from person to person and it also depends on the difficulty of the item itself.

Response time and accuracy   

How, then, does SlimStampen know when you’re forgetting an item? Of course, if you answer incorrectly, it’ s safe to say you have forgotten (part of) the item. However, when you answer correctly it does not always mean that you have mastered the item and won’ t soon forget it.  For example, when asked what the capital city of England is, you can probably answer ‘London’ in a flash, but what about the capital city of Norway? You may be able to come up with ‘Oslo’ but it will likely take longer, because that fact is not as active in your mind, and therefore takes more time to retrieve. In other words: the time it takes you to answer reflects how well you know a fact.  SlimStampen takes this into account by recording your response time for each item (Figure 3). 




Figure 3. A visual representation of the memory model used by SlimStampen. The red line represents the activation of a fact in memory. When this activation becomes too low (below the blue dashed line), a fact is forgotten. Every black dot represents a repetition of the fact. After the first repetition, memory activation declines quickly, but the more often a learner repeats a fact, the slower this activation declines. SlimStampen can estimate the activation level of a fact in memory and the speed at which this activation declines. To do this, SlimStampen uses response time. For a correct and quick response, memory activation of the fact is high: the learner knows this fact well. For a correct but slow response, memory activation of the fact is lower: the learner does not know this fact very well.

The rate of forgetting  

Based on the response time and accuracy of your answers, SlimStampen calculates a rate of forgetting for every item: a number that predicts how quickly you will forget an item (Sense et al., 2016). If this rate of forgetting becomes very high for an item, the program will make it a priority to show you the item again; if the number is very low, the program won’t show the item for a while. With every response you give, the rate of forgetting is updated. This way, the program adapts to your learning pace.

Passing the test

In 2009, researchers Van Rijn, Van Maanen and Van Woudenberg found that studying with SlimStampen is indeed more effective than a traditional flashcard method. In their study, groups of students studied French for fifteen minutes with SlimStampen or a flashcard system. The flashcard method consisted of dividing the French words into sets of 5 words and studying the items set by set. If all items from a set had been answered correctly, the learner would move on to practice the next set. One day after studying, the students were tested on the French words. On this test, the students who had studied with SlimStampen scored significantly higher compared to the group of students who had studied using the flashcard method (Figure 4).

Figure 4. Grades on a French test after a 15-minute learning session the day before. 1= flashcard,  4= SlimStampen. Numbers 2 and 3 represent two other learning algorithms. From: Van Rijn & Van Maanen (2009).  

More recently, a study by Wilschut and colleagues (2021) compared SlimStampen to a flashcard method called the Leitner method. In the Leitner method, items to be learned are grouped according to how well the learner knows them. All items start in one group. If a learner answers an item correctly, the item moves to the next group, and so on. For items in every next group, the learner waits a longer time before practicing them again.  Using either the Leitner flashcard method or SlimStampen, participants studied a set of English words. After a break, they were tested on the words they had studied.. Participants who studied with SlimStampen were approximately 10% more likely to give a correct answer during the study session, and approximately 8% more likely to give a correct answer on the test compared to participants who had learned with the Leitner flashcard method (Figure 5).   

These results confirm that SlimStampen is more efficient for vocabulary learning than a traditional flashcard method: students learn better, in the same amount of time.  

Figure 5. Accuracy during the study session and the test, for students who learned with SlimStampen and students who learned with the Leitner flashcard method (Wilschut et al., 2021). 



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