20 Things To Remember About Forgetting

Even though it’s used all day and night, we are usually not aware of our memory’s processes until they fail. Yet remembering and forgetting are crucial phenomena underlying learning. Here are some key facts about the forgetting process that relate to learning and instruction.

The Basics

  1. Forgetting is the inability to recall or recognize information that we think should reside in long-term memory. Recall refers to reproducing or reconstructing a memory without a specific external cue; recognition refers to identifying something you learned previously based on external cues.
  2. There is a debate as to what causes forgetting. Some researchers think that old memories that have not been recalled for a long time slowly decay (or disassociate from the network) over time. The prominent theory at this time, however, is that we forget due to interference or a failure of having the proper retrieval cues.
  3. Recalling a memory changes it. The act of reconstructing a memory makes it relatively stronger than other memories and may modify its contents.
  4. Memory failure can be caused at any of the three stages of processing: encoding (registering in long-term memory), consolidation (deep processing and stabilization), or during retreival.
  5. It is thought that long-term memories are stored as parts of schema or cognitive structures. One reason we may modify memories is to keep them consistent with our schema. This may be the reason people are known to give inaccurate accounts of events.

Reasons for Forgetting

  1. Some instances of forgetting are probably caused by not processing information in the first place. If we don’t pay attention to information or an event, then we fail to register it.
  2. At times we may attend to the information, but it doesn’t get encoded in long-term memory because it lacks connection to anything else we know. Therefore, we don’t understand it.
  3. Many instances of forgetting probably happen because retrieval cues are not connecting to the appropriate schema, even though the information is stored. Highly networked memories should be easier to retrieve.
  4. Consolidation of memories involves deep processing and associating information in a meaningful way with a network of learned information. Memories that are not consolidated are less stable.

 Types of Interference

  1. Interference is a critical factor in forgetting. Retrieving a memory probably involves pattern completion. In this theory, the cue (such as a question) activates the associated schema to complete the pattern. Interference of one type or another can lead to failure of retrieving the correct information.
  2. Retroactive interference (RI) occurs when newly learned information impedes the recall of something you previously learned. For example, if you are learning Spanish, you may not recall how to pronounce a word in French. The rules of Spanish pronunciation are interfering with this.
  3. We don’t yet know whether retroactive interference is due to the interference of competing stimuli or whether a person is actually unlearning the forgotten material.
  4. Proactive interference occurs when past memories inhibit one’s ability to retain new information. For example, you may have trouble remembering a new password because you used your previous password for years.
  5. The more similar new information is to previous knowledge, the more likely it is that interference will occur. The converse is also true.

Learning and Forgetting

  1. Forgetting happens most rapidly soon after learning something and then tapers off with the passage of time.
  2. Content that does not make sense to a person is typically forgotten first.
  3. Because reading is a more focused activity than listening (and perhaps for other reasons as well), most people are more likely to forget what is heard than what is read.
  4. Although we may forget the exact words of something we just read, we can remember the meaning of it.

Advantages of Forgetting

  1. The fact that unremarkable events are forgotten is probably a matter of survival. Forgetting trivia helps us to function throughout the day. The standard example to demonstrate this advantage is that if you remembered every parking spot you’ve ever had, how would you remember where your car is at the moment?
  2. Fairly recent research showed that forgetting may make more brain power available for other tasks. In one study, the cortex of subjects who did not have competing memories when asked to recall information did less work than those who had competing memories. See You Must Remember This.


What can learning specialists conclude from the science of forgetting?

  • For a memory to persist, the information must be attended to, deeply processed, and connected in a meaningful way with existing knowledge.
  • When it’s known that the learner’s knowledge base could compete with newly acquired information, allow the learner time to discriminate between the two types of content.
  • Practicing the retrieval of information can facilitate retention because reconstructing memories alters them and makes them “stronger.”
  • Don’t expect learners to remember trivial information. It won’t be remembered after the test.

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  1. Sue J says

    (typo: learner’s should be learners at that last line.)

    A huge issue for me is not addressing stuff that’s “similar” or gets filed as such anyway. I’m thinking math and the trouble people have remembering that no, four to the third power is not twelve…

  2. Tracy P says

    A very interesting article. I have problems with recall generally but at the moment I am having a few difficulties doing an essay on models (of translation theorists) even though I have gone over them again and again. I think your point about it being difficult to memorise information that is similar may well be the problem as the models all seem to be saying basically the same thing with just a few variations. The fast pace of the course is in my opinion part of the problem because we don’t have time to learn one model in detail before going on to the next.

  3. Connie Malamed says

    Hi Tracy,
    I’m sorry to hear that you’re having trouble with the models because of their similarities. I’m sure it’s very frustrating. I’d ask the instructor to help you clarify the differences and to give you examples of each model in action. Or perhaps you can write up the examples and that this will help you discriminate between them. Then try making a matrix with categories for each row and each column would be a different model. Then I’d fill in the matrix and see what’s common and what is different. This, along with your examples, could serve as your study guide.
    Good luck.

  4. Joanne says

    Connie, you publish the most interesting stuff. I found this post particularly interesting because of its application to memoir writing (which is something I pursue and also teach). There is an interesting book on this topic as it applies to memoir: Unreliable Truth, by Maureen Murdoch. Thanks for this very helpful post that I can apply to both writing and teaching.

  5. Connie Malamed says

    Hi Joanne,
    That book sounds interesting and so does your memoir writing class. I’m guessing that it refers to episodic memories, our memories of experiences and events. Although my article relates more to memory for learning facts and concepts, perhaps we create episodic memories around learning too. Nice to hear from you.

  6. nasser hosseini says

    Hi there!
    Please explain how to teach Reading efficiently to the students.

  7. Brian Dusablon says


    We had a lengthy discussion about “unlearning” at Up To All of Us this year. I’ll try to find the image of our brainstorming/discussion notes, but it was an interesting conversation. Can one truly forget on purpose? Can we unlearn something, or do we simply replace it with new information or use that previous knowledge as a stepping stone or reference point?

    Maybe something in Brain Rules would clarify?

    Thanks for the post. I hope it stirs up some more conversation.

  8. Connie Malamed says

    Hi Brian,
    I think it’s simply unknown — up for debate — as to whether someone literally “unlearns” or whether it’s all interference. On a physical level, you can imagine neurons losing their connections and getting new ones (perhaps this is interference) or getting atrophied through lack of use … but this hasn’t been proven. As to forgetting on purpose, that usually refers to our personal story memories — episodic memory. They say it’s hard to do. It makes me wonder how hypnotism works from a cognitive perspective. Interesting discussion.

  9. Lorena Bull, RD says

    Hi Connie,
    In my IDT program we are presently studying Learning Theory and your blog entry on “Forgetting” provides an excellent, useful summary of the information. It seems that there are many causes of both memory formation and retention. If only we could make a conscious decision for specific bits of information to be encoded into memory, at will! You mention that, “Some instances of forgetting are probably caused by not processing information in the first place.” I suppose this is what occurs in a sleep-deprived brain. The topic of the effects of sleep-deprivation on cognition is an area of research that I find interesting and can relate to personally, as can many of my classmates and colleagues, for sure. I would like to share some information on sleep deprivation that I encountered this week as I studied for my course. In one study, researchers (Florian, et al, 2011) used two methods to examine the role of increased levels of adenosine as a suspected cause of cognitive deficits that occur with sleep deprivation. The thought was that if the increased level of adenosine as a result of sleep deprivation was the cause of cognitive deficit, then cognitive deficit should be absent when the production of adenosine by glial cells is prevented, and also when the uptake of adenosine is blocked at the adenosine receptors of the hippocampus. One approach used mice that were genetically engineered so that their glial cells were unable to produce adenosine. A second approach involved the introduction of a drug that blocked an adenosine receptor in the hippocampus via a pump that was placed into the brains of non-genetically engineered mice. Researchers discovered that in both approaches, sleep-deprived mice performed as well as non-sleep deprived mice.
    Interestingly, researchers have also confirmed what many bleary-eyed, coffee-chugging people have believed, that chronic caffeine consumption works in preventing sleep-deprivation-induced cognitive deficits, explaining that caffeine is an adenosine antagonist, meaning that it blocks the effects of adenosine (Alhaider, et al, 2010).
    I would be interested in any information you or your readers have to share regarding sleep deprivation. I personally suffer from chronic partial sleep deprivation as a result of life circumstances, rather than from any organic condition or disease process, and while I do drink moderate amounts of iced tea and diet cola on a daily basis, I do not feel that the cognitive deficit is adequately ameliorated. And drinking massive amounts of caffeine is not recommended anyway because it causes negative side-effects. Hopefully, my life circumstances will improve, allowing me more time for sleep!

    Alhaider, I. A., Aleisa, A. M., Tran, T. T., & Alkadhi, K. A. (2010). Caffeine prevents sleep loss-induced deficits in long-term potentiation and related signaling molecules in the dentate gyrus. European Journal of Neuroscience, 31(8), 1368-1376. doi: 10.1111/j.1460-9568.2010.07175.x.

    Florian, C., Vecsey, C. G., Halassa, M. M., Haydon, P. G., & Abel, T. (2011). Astrocyte-derived adenosine and a1 receptor activity contribute to sleep loss-induced deficits in hippocampal synaptic plasticity and memory in mice. Journal of Neuroscience, 31(19), 6956. doi: 10.1523/JNEUROSCI.5761-10.2011

  10. kevin says

    The brain doesn’t actually understand ‘dont forget X’ – you’re telling it ‘not to do’ and ‘do it’ simultaneously. As in most good ‘brain’ books.

  11. Stephanie Richie says

    Hi Connie,

    Thanks for providing such a thought provoking post.

    Things to remember about forgetting! One of the courses I teach is English Composition, and students always ask; why do I need to remember this? And more times than often, those same students perform poorly on testing. Learning the material is not enough alone to recall information when needed; being able to make a correlation and connection to the material is beneficial.

    Presently, in my ID Program, Learning Theories and Instruction class, we are dealing with how the brain works, how we learn, and how we process information. Remembering is a vital part of the learning process and forgetting is in my opinion equally vital. Forgetting is so much a part of our daily routines that we ‘forget’ that we’ve forgotten. Our text points out much of the key factors you presented on interference and the decay of the long or short term memory. “…synapses (junctions between neurons) can deteriorate with lack of use in the same way muscles do with nonuse.” (Ormrod, 2009)

    I’ve challenged my students to make meaningful connections with new material they are learning so that the information can be recalled in an efficient manner. And, yes, I did give 30 minute lecture on how the use of English Composition is intertwined with basically everything we do in our lives.

    Ormrod, J., Schunk, D., & Gredler, M. (2009). Learning Theories and Instruction (Laureate Custom Edition). New York: Pearson.


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