Want Straight A's? Mastering The Spacing Effect Is A Great Place To Start
In fact, the phenomena is known as the spacing effect (and less commonly as distributed learning), and has been demonstrated time and time again in many different academic studies! Here’s what Univeristy of Nevada, Las Vegas researcher Frank Dempster said on the subject:
“The spacing effect is one of the most dependable and replicable phenomena in the learning literature (source)”.
Spacing Effect Definition: The finding that spacing learning events out over time instead of massing them together in immediate succession boosts learning and long-term memory.
Origins
Inquiry into memory and learning dates back practically to the dawn of time, but most agree that findings near the end of the 19th century triggered the massive amounts of research specifically on the spacing effect that have followed ever since.
Ribot's Law Of Retrograde Amnesia, 1881
Much of what we know today about how the brain works has come from studies of brain disorders and diseases. Knowing this, it shouldn't be too surprising that our knowledge study about the spacing effect may have come from a French psychologist Théodule-Armand Ribot's work on understanding amneisa.
Ribot proposed Ribot’s Law of Retrograde Amnesia in his 1881 publication titled The Diseases of Memory. The word amnesia comes from the Greek word for forgetfulness, amnēsía (source).
Simply put, amnesia refers to partial or complete memory loss, and retrograde amnesia refers to partial or complete memory loss of information acquired prior to the onset of amnesia (source).
Ribot observed from clinical trials that memories formed closer in time to a brain injury (amnesia) are impaired to a higher degree than memories formed longer in time before the injury. The key insight from Ribot’s Law is that the more time memories have to consolidate, the less vulnerable they become to impairment as a result of trauma to the brain (Wixted, 1).
Ribot’s Law stated another way:
“Memories formed prior to brain damage are impaired, but the effect depends on the age of the memory trace at the time the damage occurs, with more recently formed memories suffering the most (source)”.
“Although the field of experimental psychology has yet to fully embrace this way of thinking, consolidation theory is regarded as a standard model in the field of neuroscience (source).”
Ribot proposed Ribot’s Law of Retrograde Amnesia in his 1881 publication titled The Diseases of Memory. The word amnesia comes from the Greek word for forgetfulness, amnēsía (source).
Simply put, amnesia refers to partial or complete memory loss, and retrograde amnesia refers to partial or complete memory loss of information acquired prior to the onset of amnesia (source).
Ribot observed from clinical trials that memories formed closer in time to a brain injury (amnesia) are impaired to a higher degree than memories formed longer in time before the injury. The key insight from Ribot’s Law is that the more time memories have to consolidate, the less vulnerable they become to impairment as a result of trauma to the brain (Wixted, 1).
Ribot’s Law stated another way:
“Memories formed prior to brain damage are impaired, but the effect depends on the age of the memory trace at the time the damage occurs, with more recently formed memories suffering the most (source)”.
“Although the field of experimental psychology has yet to fully embrace this way of thinking, consolidation theory is regarded as a standard model in the field of neuroscience (source).”
Ebbinghaus And The Forgetting Curve, 1885
The name “Ebbinghuas” has become closely associated with the spacing effect, and for good reason! Herman Ebbinghaus was a German psychologist who is taken by most to be the discoverer!Ebbinghaus devised an inventory of nonsense, single syllable sounds. The sounds were made by sandwiching a vowel in between two consonants, and were intended to have no meaning whatsoever. Here are some examples:
RUR, HAL, MEK, BES, SOK, DUS (source).
In total, Ebbinghaus came up with just slightly more than 2,000 nonsense sounds, which he randomly divided into lists of 7 - 36 sounds. He then worked diligently to memorize each list, and documented his results every step of the way.
He experimented with the length of the intervals between memorizing a list, and testing his recall. The intervals he used were 20 minutes after studying, then an hour, then a day, and lastly, a week.
He derived a mathematical equation from his results, which he published in his 1885 work titled Memory: A Contribution to Experimental Psychology. Ebbinghaus’s equation was later plotted as a graph known as the forgetting curve.
To quote Ebbinghaus:
“With any considerable number of repetitions, a suitable distribution of them over a space of time is decidedly more advantageous than the massing of them at a single time (source)."
In the forgetting curve equation, R represents memory retention, s represents relative strength of memory, and t represents time (source).
To quote Ebbinghaus:
“With any considerable number of repetitions, a suitable distribution of them over a space of time is decidedly more advantageous than the massing of them at a single time (source)."
Jost's Law Of Forgetting, 1897
Not longer after Ribot and Ebbinghaus made their contributions, an Austrian psychologist named Adolf Jost brought more incredibly valuable knowledge to the table. Jost formulated Jost’s Law Of Forgetting in 1897.
Jost’s Law basically states that when two memories are equal in strength, but different in ages, the memory formed first will be strengthened the most from extra learning trials. Also, the memory formed first will decay more slowly than the younger memory over a given time interval (source).
The vital works of Ribot, Ebbinghaus, and Jost, paved the way for a large body of research on the subject, which followed in both the 20th and 21st centuries. Most modern research still confirms the ideas of Ebbinghaus, Ribot, and Jost.
“Fads come and go in psychology, but research on the spacing effect has withstood the test of time and significance; it continues to yield new discoveries and ideas relevant to other areas of psychology (source).”
The vital works of Ribot, Ebbinghaus, and Jost, paved the way for a large body of research on the subject, which followed in both the 20th and 21st centuries. Most modern research still confirms the ideas of Ebbinghaus, Ribot, and Jost.
“Fads come and go in psychology, but research on the spacing effect has withstood the test of time and significance; it continues to yield new discoveries and ideas relevant to other areas of psychology (source).”
Spacing Effect Experiment Design:
Now let's take a look at how a typical spacing effect experiment is designed in modern times. As we'll see, not all studies follow this setup, but it's helpful to understand the basic principals.Information is initially studied by the participants, and then the participants review the information again after a time interval called the spacing gap elapses. There will always be at least two study sessions: the initial learning session, and a review session, but multiple review sessions are common.
The time period between the last review session and the final test is called the test delay. In typical experiments, the spacing gap is manipulated, while the test delay is fixed in advance.
After the participants review the information for the last time before the final test, another time interval called the test delay between the final review session and the final test. In typical experiments, the spacing gap is manipulated, while the test delay is fixed in advance (source).
| This figure shows the components of a typical experiment, as was described above. Inspired by Figure 1 by Sharen K. Carpenter. |
Test delay: The time interval between the last study session and the final test.
Group 1 contained 8 rats that were trained using four trials per day for four days in a row, with a 1 minute interval between trials. Group 2 contained 5 rats that were trained using 16 trials in one day, also with a 1 minute interval between trials. The rats in both groups were escaping the maze faster by the final trial, but the rats in the spaced condition were escaping faster than those in the massed condition.
The results showed that the group trained with the spaced trials outperformed the group trained with massed trails; the rats trained with spacing trials required less time to navigate through the maze to the platform. While the results of the first experiment showed that the animals trained with spacing methods did better at the task, the proportion of neurons rescued in each group was roughly the same.
You guessed it, the food chain was the topic the researchers tested the children on during the experiment. None of the children had been taught anything about the food chain in school before the study was conducted, so presumably it was all new information for them unless they had parents who put on Bill Nye a lot around the house.
The children in the massed condition were given four lessons--one after the other--in the same day, while the children in the spaced condition were given one lesson a day for 4 days. The children in the clumped condition were given two lessons in immediate succession on the same day when the children in the massed condition were taught, and then another two lessons that were also in immediate succession the next day. Each condition had exactly 12 children in it.
The children were given a pre-test before they were given the lessons, and then an identical post-test after they were given all of the lessons, in which the questions were designed to gauge generalization. Interestingly, the children's change in performance in the clumped and massed conditions were roughly equivalent, and the children's change in performance in the spaced group was much better.
This study not only gives us more evidence that spaced learning is superior over massed learning for memory retention, but also suggests that learning by spaced methods may boost one's ability to generalize the information to new situations.
Spaced vs Massed Practice
During massed practice, the same information is studied immediately after it’s first learned. An example of doing massed practice would be reciting the definition of a vocabulary word from memory, checking your recall against the actual definition, and then reciting the definition again with virtually no pause in between recitations.
Here's a chance to test your understanding so far!
Here's a chance to test your understanding so far!
Pop quiz: How long would the spacing gap be in an experiment where the participants are trained at a task using massed practice?
A. 0 seconds
B. 1 second
C. 1.5 seconds
D. 2 seconds
E. Not sure!
If you guessed anything except for answer A, your guess was incorrect! Trials are said to be massed when the spacing gap is set to 0 seconds such that study sessions on the same information happen back to back.
B. 1 second
C. 1.5 seconds
D. 2 seconds
E. Not sure!
If you guessed anything except for answer A, your guess was incorrect! Trials are said to be massed when the spacing gap is set to 0 seconds such that study sessions on the same information happen back to back.
Research Studies
We will now examine two studies that I find particularly fascinating. The first study was conducted using animals, while the second study was conducted using children in the classroom setting.
Study #1: Neurogenesis and the spacing effect, Department of Psychology at Rutgers University
The main purpose of this study wasn't necessarily to demonstrate the spacing effect, but the whole experiment relied on it being observed. Before we go any further into the study, it's important understand some background information.The neuron (also known as the nerve cell) is the main functional unit of the nervous system. In popular culture, neurons are sometimes called simply “brain cells.” Neurons process and transmit information between other nerve cells, muscles, and glands, using electro-chemical signaling.
New neurons are formed from precursors in the dentate gyrus of the hippocampal formation, which is a central brain region involved in learning and memory. This process is known as neurogenesis, and generates thousands of new neurons continuously each day. The average human brain is made up of approximately 100 billion neurons.
Out of the thousands of neurons created daily, the majority of them die shortly after their birth. The researchers in the study hypothesized that rats trained with spaced trials would have more neurons rescued from death than rats trained with massed trials.
The study consisted of two experiments. In the first experiment, Sprague-Dawley rats (a common rat strain used in research) were injected with bromodeoxyuridine to detect the formation of new neurons.
The researchers hypothesized that more new neurons would be saved from death in a group of rats trained with spacing trials, than in a group of rats trained with massed trials. training
The researchers then divided the rats into two groups, where one group of rats (group 1) were trained to complete a task using spaced trials, and the other group (group 2) were trained to complete the same task using massed trials.
The time it took for the rats to go through the maze to reach a platform was measured during each trial. The video below does an outstanding job of demonstrating how the Morris Water Maze is used in experiments! I'd highly recommend watching it!
The researchers hypothesized that more new neurons would be saved from death in a group of rats trained with spacing trials, than in a group of rats trained with massed trials. training
The time it took for the rats to go through the maze to reach a platform was measured during each trial. The video below does an outstanding job of demonstrating how the Morris Water Maze is used in experiments! I'd highly recommend watching it!
Group 1 contained 8 rats that were trained using four trials per day for four days in a row, with a 1 minute interval between trials. Group 2 contained 5 rats that were trained using 16 trials in one day, also with a 1 minute interval between trials. The rats in both groups were escaping the maze faster by the final trial, but the rats in the spaced condition were escaping faster than those in the massed condition.
The results showed that the group trained with the spaced trials outperformed the group trained with massed trails; the rats trained with spacing trials required less time to navigate through the maze to the platform. While the results of the first experiment showed that the animals trained with spacing methods did better at the task, the proportion of neurons rescued in each group was roughly the same.
"There were no differences in the proportion of cells that differentiated into neurons between animals trained with massed or spaced trials."
After the first experiment showed virtually no difference between the two groups in the proportion of surviving brain cells, the researchers then conducted a second experiment with different rats. This time, they proceeded to test the hypothesis that spaced training doesn't necessarily lead to more learning compared to massed training, but that it "increases the persistence and strength of the memory."
In the second experiment the researchers set up a spaced condition with 7 rats, and a massed condition with 5 rats. The same spatial maze used in the first experiment was used again. This time, both groups were tested two days after the end of their training, and then again two weeks after the end of their training.
Two days after training, both groups performed roughly the same on the task, but two weeks after the training, the group trained with spaced trials performed better on average than the group trained with massed trials. The group trained with spacing trials only took 14 seconds on averaged to run through the maze and reach the platform, while it took the group trained with massed trials 40 seconds on average to reach the platform.
The researchers observed a significant correlation between memory and the number of brain cells formed for the rats trained with spacing methods. However, no such correlation was found for the rats trained with massed methods.
This study demonstrates that incorporating the spacing effect as a learning method can lead to stronger memories that are more persistent over time.
While this was part of it, the researchers were also interested in seeing how the spacing effect relates to generalization.
Generalization Definition: A person's ability to apply information or a concept learned to a new situation.
Unlike the previous study, in which rats were the subjects, children were the subjects here. The subjects were first and second graders whose ages ranged from 5 to 7 years old. The children were randomly divided up into one of three groups: a massed condition, a spaced condition, and a clumped condition, which consisted of a combination of massed and spaced learning methods.
Do you remember studying the food chain back in elementary school? If your teacher didn't take the spacing effect into account when they taught this to you, you probably don't remember it anymore (okay, I'm joking), so here's how the food chain is defined in the study:
"Food chains are the ways in which energy is transferred from one living thing to another within a particular biome."
If it's not all coming back yet, here's a very engaging YouTube video on the topic that should teach you everything you ever wanted to know about the food chain, but were afraid to ask:
Study #2: Distributing Learning Over Time: The Spacing Effect in Children’s Acquisition and Generalization of Science Concepts
Like the previous study, the purpose of this experiment wasn't just to test whether or not the spacing effect exists.While this was part of it, the researchers were also interested in seeing how the spacing effect relates to generalization.
Generalization Definition: A person's ability to apply information or a concept learned to a new situation.
Unlike the previous study, in which rats were the subjects, children were the subjects here. The subjects were first and second graders whose ages ranged from 5 to 7 years old. The children were randomly divided up into one of three groups: a massed condition, a spaced condition, and a clumped condition, which consisted of a combination of massed and spaced learning methods.
Do you remember studying the food chain back in elementary school? If your teacher didn't take the spacing effect into account when they taught this to you, you probably don't remember it anymore (okay, I'm joking), so here's how the food chain is defined in the study:
"Food chains are the ways in which energy is transferred from one living thing to another within a particular biome."
If it's not all coming back yet, here's a very engaging YouTube video on the topic that should teach you everything you ever wanted to know about the food chain, but were afraid to ask:
You guessed it, the food chain was the topic the researchers tested the children on during the experiment. None of the children had been taught anything about the food chain in school before the study was conducted, so presumably it was all new information for them unless they had parents who put on Bill Nye a lot around the house.
The children in the massed condition were given four lessons--one after the other--in the same day, while the children in the spaced condition were given one lesson a day for 4 days. The children in the clumped condition were given two lessons in immediate succession on the same day when the children in the massed condition were taught, and then another two lessons that were also in immediate succession the next day. Each condition had exactly 12 children in it.
The children were given a pre-test before they were given the lessons, and then an identical post-test after they were given all of the lessons, in which the questions were designed to gauge generalization. Interestingly, the children's change in performance in the clumped and massed conditions were roughly equivalent, and the children's change in performance in the spaced group was much better.
This study not only gives us more evidence that spaced learning is superior over massed learning for memory retention, but also suggests that learning by spaced methods may boost one's ability to generalize the information to new situations.
How To Apply This To Your Studying
There are two ways to incorporate the spacing effect into your studying. The first method is to use your intuition to determine how often you should review material. In Make It Stick: The Science of Successful Learning by Peter C. Brown, Brown suggests that the optimal length of time to wait between study sessions is just long enough that some forgetting has occurred, but not so long that you've forgotten the material entirely.
If you can recall learned material again effortlessly during your second study session, then the interval wasn't long enough. It should be challenging to try to recall the material, but not to the point of frustration.
In addition to the intuitive approach, you can also use a program with a computer algorithm to approximate the optimal intervals for like SuperMemo, Anki, and Quizlet.
SuperMemo is a computer program that uses an algorithm to approximate the optimum time intervals between study sessions for long-term retention. At the program’s launch back in 1987, SuperMemo used what's known as the SM-2 algorithm to approximate the intervals.
In addition to the intuitive approach, you can also use a program with a computer algorithm to approximate the optimal intervals for like SuperMemo, Anki, and Quizlet.
SuperMemo is a computer program that uses an algorithm to approximate the optimum time intervals between study sessions for long-term retention. At the program’s launch back in 1987, SuperMemo used what's known as the SM-2 algorithm to approximate the intervals.
Given that this was a long time ago, we should add that SuperMemo has since upgraded to the SM-17 algorithm. Anki is a newer spaced repetition flashcard system that's based on the same algorithm, but with slightly different features.
While some students use these systems successfully, many say the major drawback is that they’re both pretty complicated to learn how to use. I've never personally used SuperMemo, but I used to use Anki regularly to study. I can testify that Anki does have a somewhat steep learning curve, but it is pretty awesome once you get the hang of how to use it!
While some students use these systems successfully, many say the major drawback is that they’re both pretty complicated to learn how to use. I've never personally used SuperMemo, but I used to use Anki regularly to study. I can testify that Anki does have a somewhat steep learning curve, but it is pretty awesome once you get the hang of how to use it!
For the sake of simplicity, I highly recommend using Quizlet's long-term learning mode, which is based on spaced repetition. The only downside is that you have to pay to upgrade to Quizlet Pro to use this feature.
Although Quizlet is not nearly as powerful as Anki or SuperMemo, with a little creativity, you can utilize many of the best features of Anki and SuperMemo within your Quizlet decks! I'm going to show you how to do this right now!
Although Quizlet is not nearly as powerful as Anki or SuperMemo, with a little creativity, you can utilize many of the best features of Anki and SuperMemo within your Quizlet decks! I'm going to show you how to do this right now!
Flashcard Study Tips
These tips can be used for making flashcards with a system like Anki, SuperMemo, or Quizlet, or for making flashcards by hand. Many studies have shown that writing facts down by hand helps you remember them better, so this is the main benefit to making your flashcards by hand. However, I prefer to use Quizlet just because it's a lot faster to just type the cards out.
Designing your flashcards for maximum efficiency is a topic that could take up an entire blog post itself, but I want to briefly highlight a few tricks you can start using now. Back in 1999, the creator of SuperMemo, Dr. Plotr Wozniak, wrote an article titled "Effective learning: Twenty rules of formatting knowledge". This article was really influential for me back when I was as in undergrad, not just for making flashcards, but for improving my study skills in general.
I can't recommend for you to read this article enough! Seriously, it's that informative! The tricks I'm about to show you were influenced in part by Dr. Wozniak's work.
The first trick is to always try to minimize the amount of info you put on each card. This is best illustrated with an example. Suppose Becky is a student in a biology class and writes the following down in her notes during a lecture:
Blood contains red blood cells (aka erythrocytes, transport oxygen), white blood cells (aka leukocytes, immune response), platelets (blood clotting, involved in converting fibrinogen to fibrin), and plasma (liquid portion).
In order to memorize this, she makes the following flashcard on Quizlet:
Keep in mind that this is just one card that covers only a tiny fraction of the total notes that Becky needs to memorize! The first time Becky cycles through her deck and gets to this card, she is able to recall recall the first two components of the blood, and she recalls the two facts associated with red blood cells, but can’t recall any of the other components, or their associated facts. After reviewing this card, Becky puts it in the bottom of the deck and works on some other cards.
To be clear, when Becky studies this card, she only has to answer true or false. She doesn’t need to recite the explanation; she merely included it for reference.
Again, when Becky reviews this card, she only has to pick answer choice B, she doesn’t have to recite the explanation; it’s only there incase she wants to reference it (but it wouldn’t hurt to read it quickly each time she checks the answer!).
When she gets back to the card for the second time, she is able to recall the same info as she was the first time, and also remembers another fact associated with white blood cells, but she’s unable to recall the rest of the information!
It’s certainly possible for Becky to memorize everything this way, but there’s a much better way to go about it! Becky would be much better off if she broke the information down into smaller, simpler chunks. To illustrate this, let’s focus on just her notes for the first component of blood:
Blood contains red blood cells (aka erythrocytes, transport oxygen).
The simplest way to make a great flashcard out of this is to use the underscore key to “blank out” parts of the notes. To do this, simply hold down the shift button and press the key highlighted in red immediately to the left of the plus/equals sign key, shown on the keyboard below. Depending on the type of computer you’re using, you may or may not need to press enter after.
Another very simple way Becky could make excellent flashcards is to take each bit of information and turn it into a separate question. For example:
The advantage of this method over the first is that there is less information on the cards, making it even faster for Becky to review them. The third method involves making true/false statements, just like this:
Please note how Becky included a brief explanation in the first true/false section. Another awesome perk to using Quizlet is that you can put a virtually unlimited amount of information on the card!
It’s certainly possible for Becky to memorize everything this way, but there’s a much better way to go about it! Becky would be much better off if she broke the information down into smaller, simpler chunks. To illustrate this, let’s focus on just her notes for the first component of blood:
Blood contains red blood cells (aka erythrocytes, transport oxygen).
The simplest way to make a great flashcard out of this is to use the underscore key to “blank out” parts of the notes. To do this, simply hold down the shift button and press the key highlighted in red immediately to the left of the plus/equals sign key, shown on the keyboard below. Depending on the type of computer you’re using, you may or may not need to press enter after.
The basic principle here is very similar to what SuperMemo and Anki users call making a “cloze deletion.” Here’s an example of some of the Quizlet cards she could create using this method:
Please note how Becky included a brief explanation in the first true/false section. Another awesome perk to using Quizlet is that you can put a virtually unlimited amount of information on the card!
To be clear, when Becky studies this card, she only has to answer true or false. She doesn’t need to recite the explanation; she merely included it for reference.
The fourth and final method that we’re going to cover here may require a little more creativity for some, but it can be devastatingly effective when it’s done well! This method is what we call the multiple choice method. It basically involves picking part of the information that you’d like to learn, and then making up "bogus" answer choices. Here’s an example of one way Becky could do this:
Again, when Becky reviews this card, she only has to pick answer choice B, she doesn’t have to recite the explanation; it’s only there incase she wants to reference it (but it wouldn’t hurt to read it quickly each time she checks the answer!).
We’ve just seen how Becky can design flashcards for the first part of her notes using the 4 different methods we’ve outlined here. As a summary, here are the four methods:
1. Single missing keyword cards
2. Single question cards
3. True/false cards
4. Multiple choice cards
In practice, Becky would finish making cards out of the rest of this section of the notes, and would then repeat the process for the rest of her notes from this lecture. Her goal would be to cover everything important using at least 2 - 3 different methods. She would then shuffle the deck completely, so that the questions would be fed to her in random order.
The whole point here is that after optimizing her deck for maximum efficiency, Becky would then study using the Quizlet long-term learning feature or Anki/SuperMemo, either of which would automatically determine the best intervals for her based on her performance. For example, she would be would shown the cards she needs the most work on more frequently than the cards she knows the best.
1. Single missing keyword cards
2. Single question cards
3. True/false cards
4. Multiple choice cards
In practice, Becky would finish making cards out of the rest of this section of the notes, and would then repeat the process for the rest of her notes from this lecture. Her goal would be to cover everything important using at least 2 - 3 different methods. She would then shuffle the deck completely, so that the questions would be fed to her in random order.
The whole point here is that after optimizing her deck for maximum efficiency, Becky would then study using the Quizlet long-term learning feature or Anki/SuperMemo, either of which would automatically determine the best intervals for her based on her performance. For example, she would be would shown the cards she needs the most work on more frequently than the cards she knows the best.
