How To Remember Everything You Learn and the Effects of Sleep on Memory

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Do you ever catch yourself frustrated that you're unable to remember what you just learned? How much of what you studied in school do you still remember?

We spend countless hours every year reading books, listening to podcasts or news, and watching educational content. A lot of what we learn is forgotten. Research shows that more than half of the information we learn is forgotten in the first hour [1]

Fig 1. below shows the data from the 4 experiments run where 1.0 is 100 percent of the information retained and 0.0 means all information is forgotten

Fig 1. Retention over time

Our Brains have a limited capacity to store information and forgetting is a normal phenomenon for humans to help us continue to make space for learning new information. In this article, we'll get a better understanding of how and why we forget, understand the impact of sleep on memory, and finally cover the most efficient techniques for enhancing your ability to retain what you learn

Why we forget

In Experimental Psychology, there are two methods by which the brain can forget information, passive forgetting and active forgetting[2]

Passive Forgetting

  • Natural Decay: Biological Decay of memory traces over time.
  • Retrieval Interference: The accumulation over time of similar memory traces that impede proper retrieval of wanted one or changes in memory's context between acquisition and retrieval that impair efficient recall

Active Forgetting

  • Interference-based forgetting:  brain activity due to new information presented before or after the learning event that reduces the efficiency of storing the memory
  • Motivated forgetting: suppressing memory during recall or consolidation voluntarily for example negative memories, can disrupt memorization and cause forgetting
  • Retrieval-induced forgetting: Practiced recall of an item from a category can weaken recall of other items from the same category and to an even bigger extent weakening of recall of items from other categories
  • Intrinsic forgetting: Brains ability to erode memories through signaling similar to the ones used for memory consolidation

We can see from the many ways the brain can forget described above, a lot has to do with how much interference we have with the process of memorization and consolidating those short-term memories to the long-term memory. In other words, concentration is a key here to memorization.

The Forgetting Curve

In Memory Research Hermann Ebbinghaus published his first study about the forgetting curve in German, which was later translated to be called Memory: A contribution to Experimental Psychology.[3]

He hypothesized that the speed of forgetting depends on several factors

  • Sleep
  • Stress
  • The difficulty of the material
  • Representation (the rate of forgetting is different from one person to another due to the mnemonic representation skills )
  • Concentration

And the best practices to increase the strength of memory are

  • Better memory representation
  • Using Spaced repetition with active recall
  • Later research shows that the bigger the payload of information initially learned the slower we forget them[4]

We will describe what those techniques are and how to apply them in the Memorization Enhancement Techniques section but first, let us take a look into the impact of sleep on memory

Impact of Sleep on memory

Research shows that sleep has a significant impact on our memory retention. A typical 8 hours of sleep starting at 11 and ending at 7 goes through a sleep cycle consisting of 90 minutes intervals, every 90 minutes the brain goes through the stages of sleep REM(Rapid Eye Movement), NREM(Non-Rapid Eye Movement) (NREM stage 1, stage 2), and (NREM stage 3, and 4 (slow-wave sleep)) and back up. [5]

A burst of brainwave activity that happens at the tail end of each slow wave during the NREM sleep in both the deep and light stages of NREM is called a Sleep spindle. One of their functions is to shield the brain from noises and the stronger they are the harder it is for a person to wake up from external noises. They also affect our learning ability replenishment[5]

During wakefulness, the brain is constantly absorbing new information. For the fact-based types of information like learning names, phone numbers, etc. New Information is stored in the hippocampus region of the brain (short-term memory). The hippocampus has limited storage capacity, when it's exceeded we either are unable to learn new information or we start to overwrite other information learned earlier (interference forgetting explained in the previous section)[5]

The Effect of Sleep on Remembering

Mathew P. Walker a professor of Neuroscience and Psychology has written a very extensive book on the subject of sleep and its impact on all aspects of life called Why We Sleep: Unlocking the Power of Sleep and Dreams I highly recommend reading

His research team ran several experiments on volunteers to better understand the impact of sleep on memory. They took the participants and split them into two groups one group would be given the ability to nap/ sleep before and after learning while the other stays awake.

They found that the group who was able to sleep between their first and second learning session had a 20% increase in learning capacity and it was correlated to the number of sleep spindles the individual obtained during the nap. They also observed a loop of the electrical current pulsing between the hippocampus (short term memory) and the cortex (long term memory) effectively clearing out the hippocampus and persisting information. An interesting observation here is that the sleep spindles were most concentrated in the late morning hours of NREM sleep in general this portion has a shorter NREM duration of the cycle but a higher concentration of sleep spindles

Other experiments that were done on sleeping 8 hours right after learning vs staying awake showed that there's a 20 to 40 percent enhancement in memory retention of learned material when those hours were spent sleeping. Furthermore, experiments were done to see the impact on sleeping the first half of the night full in NREM sleep vs the second half which is dominated by REM. The results were clearly the more NREM sleep the individual had the more memory retention they had.[5]

When the researchers investigated where the memories were being retrieved from before and after sleep they found the hippocampus was being used to retrieve the information before sleep (short-term memory, volatile) while after the sleep period it was being retrieved from the neocortex (long term more persistent memory). Also, sleep was observed to improve the ability to retrieve lost memories that were lost soon after learning

The Effect of Sleep on Forgetting

Walker and a graduate student decided to test the hypothesis of Francis Crick that REM sleep function was to remove unwanted memories. Another experiment was run with participants given a series of words to memorize but they were given a green R or red F after each word indicating whether they should remember or forget. Testing participants who got 90-minute nap vs ones that stayed awake, they found out that sleep was selective about which words to boost retention for and focused only on the ones marked to remember vs the control group however it was not due to REM sleep it was still due to NREM sleep and more specifically correlated to the sleep spindles

They also noticed another circuit here that ran between the hippocampus and the frontal lobes that may explain the ability of the brain to be selective about what to memorize based on tags previously marked on these memories

Memorization Enhancement Techniques

Sleep

As we've observed from the previous section sleep has a significant impact on replenishing our ability to learn new information. Boost retention of newly learned information as well as eliminate information we no longer need which helps our recall of information we do want to remember and makes more space for future information.

Use naps and full 7 - 9 hours of sleep to boost your learning

Spaced Repetition

An Evidence-based technique. Observed in Ebbinghaus Research as well as future studies.[1][3] This shows that spaced repeated learning aids in remembering by offsettings the natural decay of information and reinforcing those pathways in your brain. A typical schedule is after 1 hour, 1 day, 1 week, 2 weeks, 1 month, six months, once a year. At each repetition schedule if the information is recalled correctly it falls to the next level. if not recalled falls back into the more frequent bucket

It is also important to keep your sessions to 30 - 45 minutes and take breaks. research shows that after 50 minutes the brain loses the ability to focus significantly.[6]

There are many software out there that can help with this

Active Recall

Two factors come into play when studying

  • Levels of Processing Effect (Craik & Lockhart, 1972) - the more you process a given piece of information, the better you remember it.[9]
"the meaningfulness extracted from the stimulus rather than in terms of the number of analyses performed upon it." (1973, p. 48)
  • The Generation Effect (Slamecka & Graf, 1978) - actively recalling a given piece of information increases your chances of consolidating it in your long-term memory.[10]

When studying it's important to pause, contemplate the information you are reading, and reason about it. This will help increase the chances of retention. You can try jotting it down as a way to slow yourself down and visualize the information

Use active recall by tagging the information with a question and then read the question and attempt to recall the information. Research shows that it is the most efficient way to study written materials.[7]Also, more efficient than other techniques like note taking[8]

Reduce Stress

While studies show that stress may help enhance memory formation only when triggered shortly before or after learning, specially if the information is realted to the stressor. It also shows that stress episodes long before learning impars memory formation. As for retrieval time, stress impedes recall of information previously learned and it also impedes subsequent updates to these memories. [11][12]

Exercise and practice breathing techniques and meditation to control and reduce your stress

Concentration

We learned that interference-based forgetting can weaken our ability to consolidate memories. When learning something new avoid distractions before, during, and after your learning session. If possible take a nap to consolidate this information in your long term memory

Enhance your Mnemonic Techniques

We've learned that better representation of the information had an impact on how long you can naturally retain them. Here are some techniques to help

Feature mnemonics: Trying to remember someone's name and associate it with their face example "bearded brad"

Rhyming mnemonics: In fourteen hundred and ninety-two, Columbus sailed the ocean blue"

Acronyms: For example, MIT to represent Massachusetts Institute of Technology

Organization mnemonics: For example breaking phone numbers into 3 parts to help memorize it

Visual Mnemonics: Using a technique like Memory Palace (Method of Loci). Build a story and visualize it. Place your items in different areas in an environment you're familiar with and you'll be able to walk through that environment in your mind and grab those items from those locations

Summary

We learned what are the reasons for forgetting passively and actively, and that It is natural for us to forget so we can make space for new information. We learned about the forgetting curve and how information decay over time and how to offset that curve with spaced repetition and active recall. We discussed sleep stages and the stages that impact our learning and how to use sleep to our advantage and finally discussed some techniques for improving your learning Via using Spaced repetition, active recall, concentrating, taking breaks, and using mnemonics.

References

[1] Murre, Jaap M. J.; Dros, Joeri (2015). "Replication and Analysis of Ebbinghaus' Forgetting Curve". PLOS ONE. 10 (7): e0120644. doi:10.1371/journal.pone.0120644. PMC 4492928. PMID 26148023
[2]DOI:https://doi.org/10.1016/j.neuron.2017.05.039
[3]Memory: A Contribution to Experimental Psychology -- Ebbinghaus (1885/1913)". Retrieved 2007-08-23.
[4]Loftus, Geoffrey R. (1985). "Evaluating forgetting curves" (PDF). Journal of Experimental Psychology: Learning, Memory, and Cognition. 11 (2): 397–406. CiteSeerX 10.1.1.603.9808. doi:10.1037/0278-7393.11.2.397
[5]Walker, Matthew P. Why We Sleep: Unlocking the power of Sleep and Dreams. Simon & Scribner, 2017
[6]University of Illinois at Urbana-Champaign. "Brief diversions vastly improve focus, researchers find." ScienceDaily. ScienceDaily, 8 February 2011. www.sciencedaily.com/releases/2011/02/110208131529.htm.
[7]Nilson, Linda (2010). Teaching at Its Best: A Research-Based Resource for College Instructors. San Francisco, CA: Jossey-Bass. p. 296. ISBN 9780470401040.
[8]Dunlosky J, Rawson KA, Marsh EJ, Nathan MJ, Willingham DT. (2013). "Improving Students' Learning With Effective Learning Techniques: Promising Directions From Cognitive and Educational Psychology". Psychol Sci Public Interest. 14 (1): 4–58 doi:10.1177/1529100612453266
[9]Craik, F. I. M., & Lockhart, R. S. (1972). Levels of processing: A framework for memory research. Journal of Verbal Learning and Verbal Behavior, 11(6), 671.
[10]Slamecka, N. J., & Graf, P. (1978). The generation effect: Delineation of a phenomenon. Journal of Experimental Psychology: Human Learning and Memory, 4(6), 592–604. https://doi.org/10.1037/0278-7393.4.6.592
[11]Shields GS, Sazma MA, Mccullough AM, Yonelinas AP. The effects of acute stress on episodic memory: A meta-analysis and integrative review. Psychol Bull. 2017;143(6):636-675. doi:10.1037/bul0000100
[12]Vogel, S., Schwabe, L. Learning and memory under stress: implications for the classroom. npj Science Learn 1, 16011 (2016). https://doi.org/10.1038/npjscilearn.2016.11