July 18

The Forgetting Curve (and a Reason to Remember)


We know it happens, both to our students and in our own lives—we forget. There are whole days we can’t remember (quick—what were you doing on February 4, 2018? See!), whole books we don’t remember reading, and names of individuals we have met but can’t call to mind. We have taught our students particular skills or concepts, but they act like it’s new content when they get to the next grade level. Of course, it’s obvious that our minds can’t retain everything, and that in the onslaught of news, memes, and social-media-scrolling, we shouldn’t. But in a classroom setting where the main goal is to help students gain new skills and concepts, it’s our job to be sure they do. So what’s going on, and how can we change this?

In 2017, Edutopia featured an article called “Why Students Forget and What You Can Do About It,” which introduced me to Ebbinghaus’ Forgetting Curve, a graph of how much of something we forget each day. It’s discouraging. Take a look:File:Ebbinghaus’s Forgetting Curve (Figure 1).jpg


For those of us in the education world, this is especially disconcerting. It feels like our time and effort in the classroom is being poured down the drain! Why do students forget, and what can we do when we want to ensure our students remember key skills, content, and knowledge?

Think of a memory like a pathway created in a dense jungle. Learning a new skill or new content is like creating a trail through the vegetation with a machete. If you don’t use that path and clear it often, the vines, bushes, and lush plant life will reclaim that path, just like your brain makes space for new memories by forgetting.

Our job as teachers is to keep the skills and content pathways clear for students to help them retain more of what we teach them. We want to intervene as much as possible so that the 25% retained after 6 days ends up being a much higher number. Fortunately, this can be done. By repeatedly accessing a memory, we clear the path—we strengthen the neural networks—and remember something longer than if we don’t access it again.

So what does this have to do with PBL, and what practical strategies can we use?

The Edutopia article I mentioned earlier suggests using these 5 strategies to increase student memory:

  1. Peer-to-peer explanations
  2. Review-break-review again
  3. Give frequent practice tests (formative assessments)
  4. Don’t group similar concepts (use interleaving)
  5. Pair texts with images

These strategies work especially well in a PBL context because project-based learning units often utilize cooperative learning and collaboration and rely on formative assessment. PBL units can use interleaving and reviewing of concepts, and the best PBL units also utilize readings (preferably image-rich texts). More importantly, however, PBL units give the content a storyline—a reason for the content to exist that matters to students. By enhancing the meaning and relevance of content for students, PBL gives students a reason to remember the content.

In addition to added meaning, repetition matters. Just like classic family stories that get retold at holidays and gatherings, project-based learning unit content gets revisited throughout the unit and across units, helping students retain knowledge and understanding.

Other features of memorable moments, from Chip and Dan Heath's The Power of Moments (2017), are that they have:

  • Elevation (sensory appeal, high-stakes, break the script)
  • Insight (“aha” moments, meaning-making)
  • Pride (milestones, intrinsic motivation, celebration)
  • Connection (shared meaning, shared struggle, attunement)

These are all key elements in PBL units, from the launch day (which can be a moment of elevation), through the project work (which should be full of insights from meaning-making and connection from collaboration) to the final presentation day (certainly a moment of pride).

If I may, then, add the following strategies to Edutopia's list through my PBL lens, we can have more tools in our toolkit for boosting memory:

  1. Create milestones within the unit for students to complete, and celebrate their completion
  2. Launch the unit in a memorable way that includes an appeal to the senses and that is surprising (but also requires students to engage in the unit challenge right away!)
  3. Raise the stakes by having students share their work and learning with others outside of the classroom
  4. Embed meaningful ways for students to work together in the unit
  5. Provide scaffolds and tools for students as they make sense of the content

With this combination of strategies, you now have multiple ways to change the forgetting curve, as you have given students multiple reasons to remember. So, if we want to increase students’ memories and ensure that our teaching is not in vain, let’s polish our PBL neural pathway-clearing “machetes” and get to work!


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