Why Students Forget—and What You Can Do About It
Our brains are wired to forget, but there are research-backed strategies you can use to make your teaching stick.
By Youki Terada
September 20, 2017
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Teachers have long known that rote memorization can lead to a superficial grasp of material that is quickly forgotten. But new research in the field of neuroscience is starting to shed light on the ways that brains are wired to forget—highlighting the importance of strategies to retain knowledge and make learning stick.
In a recent articlepublished in the journal Neuron, neurobiologists Blake Richards and Paul Frankland challenge the predominant view of memory, which holds that forgetting is a process of loss—the gradual washing away of critical information despite our best efforts to retain it. According to Richards and Frankland, the goal of memory is not just to store information accurately but to “optimize decision-making” in chaotic, quickly changing environments. In this model of cognition, forgetting is an evolutionary strategy, a purposeful process that runs in the background of memory, evaluating and discarding information that doesn’t promote the survival of the species.
“From this perspective, forgetting is not necessarily a failure of memory,” explain Richards and Frankland in the study. “Rather, it may represent an investment in a more optimal mnemonic strategy.”
The Forgetting Curve
We often think of memories as books in a library, filed away and accessed when needed. But they’re actually more like spiderwebs, strands of recollection distributed across millions of connected neurons. When we learn something new—when a teacher delivers a fresh lesson to a student, for example—the material is encoded across these neural networks, converting the experience into a memory.
Forgetting is almost immediately the nemesis of memory, as psychologist Hermann Ebbinghaus discovered in the 1880s. Ebbinghaus pioneered landmark research in the field of retention and learning, observing what he called the forgetting curve, a measure of how much we forget over time. In his experiments, he discovered that without any reinforcement or connections to prior knowledge, information is quickly forgotten—roughly 56 percent in one hour, 66 percent after a day, and 75 percent after six days.
So what can be done to preserve the hard work of teaching? After all, evolutionary imperatives—which prune our memories of extraneous information—don’t always neatly align with the requirements of curriculum or the demands of the Information Age. Learning the times tables doesn’t avail when running from lions, in other words, but in the modern world that knowledge has more than proved its mettle.
The Persistence of Memory
The same neural circuitry appears to be involved in forgetting and remembering. If that is properly understood, students and teachers can adopt strategies to reduce memory leaks and reinforce learning.
MIT neuroscientists, led by Richard Cho, explain the mechanisms for synaptic strengthening in a 2015 article, also published in Neuron. When neurons are frequently fired, synaptic connections are strengthened; the opposite is true for neurons that are rarely fired. Known as synaptic plasticity, this explains why some memories persist while others fade away. Repeatedly accessing a stored but fading memory—like a rule of geometry or a crucial historical fact—rekindles the neural network that contains the memory and encodes it more deeply.
Researchers have also learned that not all new memories are created equal. For example, here are two sets of letters to remember:
- NPFXOSK
- ORANGES
For readers of English, the second set of letters is more memorable—the more connections neurons have to other neurons, the stronger the memory. The seven letters in NPFXOSK appear random and disjointed, while ORANGES benefits from its existing, deeply encoded linguistic context. The word orangesalso invokes sensory memory, from the image of an orange to its smell, and perhaps even conjures other memories of oranges in your kitchen or growing on a tree. You remember by layering new memories on the crumbling foundations of older ones.
5 Teacher Strategies
When students learn a new piece of information, they make new synaptic connections. Two scientifically based ways to help them retain learning is by making as many connections as possible—typically to other concepts, thus widening the “spiderweb” of neural connections—but also by accessing the memory repeatedly over time.
Which explains why the following learning strategies, all tied to research conducted within the past five years, are so effective:
- Peer-to-peer explanations: When students explain what they’ve learned to peers, fading memories are reactivated, strengthened, and consolidated. This strategy not only increases retention but also encourages active learning (Sekeres et al., 2016).
- The spacing effect:Instead of covering a topic and then moving on, revisit key ideas throughout the school year. Research shows that students perform better academically when given multiple opportunities to review learned material. For example, teachers can quickly incorporate a brief review of what was covered several weeks earlier into ongoing lessons, or use homework to re-expose students to previous concepts (Carpenter et al., 2012; Kang, 2016).
- Frequent practice tests:Akin to regularly reviewing material, giving frequent practice tests can boost long-term retention and, as a bonus, help protect against stress, which often impairs memory performance. Practice tests can be low stakes and ungraded, such as a quick pop quiz at the start of a lesson or a trivia quiz on Kahoot, a popular online game-based learning platform. Breaking down one large high-stakes test into smaller tests over several months is an effective approach (Adesope, Trevisan, & Sundararajan, 2017; Butler, 2010; Karpicke, 2016).
- Interleave concepts:Instead of grouping similar problems together, mix them up. Solving problems involves identifying the correct strategy to use and then executing the strategy. When similar problems are grouped together, students don’t have to think about what strategies to use—they automatically apply the same solution over and over. Interleaving forces students to think on their feet, and encodes learning more deeply (Rohrer, 2012; Rohrer, Dedrick, & Stershic, 2015).
- Combine text with images: It’s often easier to remember information that’s been presented in different ways, especially if visual aids can help organize information. For example, pairing a list of countries occupied by German forces during World War II with a map of German military expansion can reinforce that lesson. It’s easier to remember what’s been read and seen, instead of either one alone (Carney & Levin, 2002; Bui & McDaniel, 2015).
So even though forgetting starts as soon as learning happens—as Ebbinghaus’s experiments demonstrate—research shows that there are simple and effective strategies to help make learning stick.
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- Youki TeradaResearch and Standards Editor@YoukiTerada
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Posted 9/21/2017 8:37am
Tracy Schiffmann
Using brain science to equip teachers of trauma-impacted adult learners to touch hearts, change minds and transform behavior
Thank you for this wonderful article that connects the science to the strategies. I design and teach a lot of behavior-change curriculum so I'm in the business of helping adult learners develop new habits. One strategy I've been using connects to Ebbinghaus' discovery that remembering requires reinforcement or connections to prior knowledge. With this in mind, I created a planning worksheet for using a new habit. One step on the worksheet is to tie the new habit to an old habit as a way to reinforce it and help the learner remember to do it. An example might be connecting flossing your teeth (new habit) to brushing your teeth (old habit). Another example might be, when you deposit your check at the bank (old habit) immediately transfer a pre-determined amount to your savings account (new habit). I love the visual picture you paint when you write, "You remember by layering new memories on the crumbling foundations of older ones." By asking learners to intentionally tie a desired new habit to an existing one, we can help reinforce both good practices!
Posted 9/21/2017 8:43am
Hi Tracy, I love how you use old behaviors (prior knowledge) to scaffold new behaviors (new knowledge)--that's a really interesting way to look at questions of retention and knowledge building generally. Thanks for your comment!
Posted 9/22/2017 1:48am
Sometimes healthy competition while playing fun games can help students to improve retention of what they learned. At the end of each lesson, I design an online quiz test for students to check what they have understood. Anf of course, the student who scores the most will be honored in front of the entire class. This imbibes a competitive spirit among students as they start paying close attention to my lessons in order to score the most in the quiz. It is a simple technique to ensure that students are attentive in the classroom. Here's an example of how the quizzes look like: http://www.cram.com/
Posted 9/22/2017 4:45am
I'm a big proponent of peer to peer learning and was witness to the power of this process a couple of weeks ago with my daughter and a friend. They both had an upcoming test using a mountain of notecards they had created over the prior weeks. The first thing I had my daughter do was to layout the cards in groupings that explained how the larger concept related to the individual items on the cards and then made her tell me the "story" of that grouping several times. Then, she and her friend did a virtual study group via Facetime in which one girl would ask the other to explain one of the definitions/theories on the card. They did this for a couple of hours, we finally had to tell them to stop. They had fun, they giggled, but they used that time to help each other make those connections to the content and the meaning behind the content. This left me with three questions: 1) Why don't teachers share strategies like these with students? 2) What would happen if teachers taught these strategies (maybe starting with sharing this article and asking students to respond)? 3) Why couldn't more class time be devoted to allowing peer to peer learning?
Posted 9/22/2017 6:26am
Love this article! This knowledge is often forgotten when teaching struggling readers. Recalling the more difficult "sight" words requires combining text with images or experience. Such words become memorable, ties learning to emotion and help students recall words. Thanks again for your work!
Posted 9/23/2017 10:32am
Very cool article! As many individual students exist is likely the number of strategies we should try, right? Oh, to get inside their minds. Or maybe NOT.
Posted 9/23/2017 11:27am
I recently sat in on a series of English courses as a T/A & tried to help the teacher keep the students' minds on-task. What is so distracting is the prevelence of smart phones. In their parents' generation, walkmen were routine collected & sent to the assistant principal. But these devices are more personalized, so kids keep them on their person. Some kids are half- focused on the topic at hand & the other part of their brains drawn to something else. Of course, the kids are also using laptops that sometimes include a audio portion & have to wear ear buds.... Frustration is revealing itself in the need for students to stand up, walk around, even go to the restroom more than once in a 90 minute period. It's no wonder when these students apply to a community college, they do not pass the English portion of their entrance exams, and then have to re-take high school courses!
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