I’ve been thinking about what some researchers call “storage strength” and “retrieval strength,” and I think there may be important implications for how we teach.
Quick Research Summary
“Our memories do not exist on a single spectrum, ranging from completely forgotten to very well remembered. Rather, how memorable something is can be indexed in two ways, as retrieval strength and as storage strength…
Retrieval strength (RS) is a measure of how easily recalled something is currently, given what is relevant to the present situation (does it come to mind now?).
- The retrieval strength of a given piece of information can be high or low, and can fluctuate back and forth between these values.
- Retrieval strength is measured by current performance (e.g., answering questions in class, on a test).
Storage strength (SS) is a measure of whether information is deeply embedded or well learned (is it likely to be recalled later?).
- Barring organic brain damage, storage strength cannot decrease; rather, it is presumed to only accumulate
- Storage strength cannot be directly measured, but must be inferred: Is that information easily recalled in the future? Or, if you forget that information, does it become faster to relearn it the next time?”
Source: The Learning Scientists blog
“… there are two indices of memory strength: storage strength (SS) and retrieval strength (RS). Storage strength is how well learned something is; retrieval strength is how accessible (or retrievable) something is. To illustrate, imagine four possible situations. If something is well learned (e.g., the address where you have lived for several years), it has both high SS and high RS: You know it well and can retrieve it readily.”
Source: UCLA Bjork Learning and Forgetting Lab
Why this might matter in our classrooms
Our goal is to help students process important ideas and skills so that they can use them in the future (to solve problems, etc.) Since that’s our goal, we want to encourage both Storage and Retrieval Strength for the important knowledge and skills in our curriculum. We should set up learning experiences for students that increase storage strength and retrieval strength for the important stuff.
|Low Storage Strength||High Storage Strength|
|Low Retrieval Strength||Forgot instantly!||Buried and lost forever (?)|
|High Retrieval Strength||Crammed!||Mastered!|
What can we do to encourage storage strength?
- Experiences that encourage students to deeply process material/skills are likely to increase storage strength. We want students to do cognitive work in their working memories that increase the chances that the information will be encoded into long term memory.
- The more “connections” students can make between the “new stuff” and “old stuff” already in their long term memory, the more deeply and strongly the new information/skills will be encoded.
- Anything you can do that helps students connect the new information to what is already in their long term memories may increase the storage strength (e.g. students generating their own examples based on their experiences, connecting material/skills with their own lives, etc.)
What can we do to encourage retrieval strength?
- The more often students have to recall information and use skills, the stronger the “retrieval strength” will be. These opportunities are called “retrieval practice.”
- If we want students to “transfer” knowledge and skills (be able to use the knowledge/skills in other contexts), retrieval strength is key!
- Offering students multiple, low-stakes opportunities to recall information and use skills will help increase retrieval strength, as long as the opportunity actually “forces” students to get that information or skill out of long term memory. These opportunities must be authentic in the sense that each student actually has to recall the information or skill.
- Asking a whole class a question and then calling on a student volunteer may be retrieval practice for that volunteer, but probably isn’t for the rest of the class. Asking everyone in class to write down the answer to a question, then asking for a volunteer, or calling on a random student, or doing a think/pair/share is more likely to be retrieval practice for each student.
- Retrieval strength is one reason to do a summative assessment (unit tests, etc.). If our goal is that students will be able to retrieve valuable knowledge/skills long after then encoded that information and use it to solve problems, summative assessments can support and reinforce that goal.
- Here’s a good 2 minute summary of retrieval practice from a cognitive psychology researcher: Three reasons why retrieval practice boosts learning