How Much Do People Forget?

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This blog post is excerpted from the full report, How Much Do People Forget? Click here to download the full report. You may also access the report—and many other reports—by going to my catalog page by clicking here.

Everybody Wants to Know—How Much Do People Forget?

For years, people have been asking me, “How much do people forget?” and I’ve told them, “It depends.” When I make this statement, most people scowl at me and walk away frustrated and unrequited. I also suspect that some of them think less of me—perhaps that I am just hiding my ignorance.

But I try. I try to explain the complexity of human learning. I explain that forgetting depends on many things, for example:

  • The type of material that is being learned
  • The learners’ prior knowledge
  • The learners’ motivation to learn
  • The power of the learning methods used
  • The contextual cues in the learning and remembering situations
  • The amount of time the learning has to be retained
  • The difficulty of the retention test
  • Etc.

More meaningful materials (like stories) tend to be easier to remember than less meaningful material (like nonsense syllables). More relevant concepts tend to be easier to remember than less relevant concepts. Learners who have more prior knowledge in a topic area are likely to be better able to remember new concepts learned in that area. More motivated learners are more likely to remember than less motivated learners. Learners who receive repetitions, retrieval practice, feedback, variety (and other potent learning methods) are more likely to remember than learners who do not receive such learning supports. Learners who are provided with learning and practice in the situations where they will be asked to remember the information will be better able to remember. Learners who are asked to retrieve information shortly after learning it will retrieve more than learners who are asked to retrieve information a long time after learning it.

I try to explain all this, but still people keep asking.

And then there are the statistics I keep hearing—that are passed around the learning field from person to person through the years as if they were immutable truths carved by Old Moses Ebbinghaus on granite stones. Here is some information so cited (as of December 2010):

  • People forget 40% of what they learned in 20 minutes and 77% of what they learned in six days (http://www.festo-didactic.co.uk/gb-en/news/forgetting-curve-its-up-to-you.htm?fbid=Z2IuZW4uNTUwLjE3LjE2LjM0Mzc).
  • People forget 90% after one month. (http://www.reneevations.com/management/ebbinghaus-curve/)
  • People forget 50-80% of what they’ve learned after one day and 97-98% after a month. (http://www.adm.uwaterloo.ca/infocs/study/curve.html)

Never mind that these immutable truths conflict with each other.

So, I will try one more time to convince the world that forgetting depends.

To accomplish this, I explored 14 research articles, examining 69 conditions to see how much forgetting occured, representing over 1,000 learners.

The following graph details the amount of forgetting for each of the 69 conditions:

 

Conclusions

This graph and the indepth analysis in the full article revealed four critical concepts in human learning—truths that every learning professional should deeply understand.

  1. The amount a learner will forget varies depending on many things. We as learning professionals will be more effective if we make decisions based on a deep understanding of how to minimize forgetting and enhance remembering.
  2. Rules-of-thumb that show people forgetting at some pre-defined rate are just plain false. In other words, learning gurus and earnest bloggers are wrong when they make blanket statements like, “People will forget 40% of what they learned within a day of learning it.”
  3. Learning interventions can produce profound improvements in long-term remembering. In other words, learning gurus are wrong when they say that training is not effective.
  4. Different learning methods produce widely different amounts of forgetting. We as learning professionals can be more effective if we take a research-based approach and utilize those learning methods that are most effective.

Telling Findings From the Research

  1. People in the reviewed experiments forgot from 0% to 94% of what they had learned. The bottom line is that forgetting varies widely.
  2. Even within a restricted time range, learners forgot at wildly differing rates. For example, in the 1-2 day range, learners forgot from 0 to 73%. Learners in the 2-8 year range forgot from 16% to 94%. The obvious conclusion here is that learning varies widely (and wildly) and cannot be predetermined (except perhaps by deities, of whom, I think, we have not even a few in the learning field). To be specific, when we hear statements like, “People will forget 60% of what they learned within 7 days,” we should ignore such advice and instead reflect on our own superiority and good looks until we are decidedly pleased with ourselves.
  3. Even when we looked at only one type of learning material, forgetting varied widely. For example, in Bahrick’s classic 1979 experiment where learners were learning English-Spanish word pairs, learners forgot from 12% to 63%. Even more remarkably, if we include those cases where learners actually remembered more on the second test than the first test, learners’ “forgetting” varied from -41% to 63%, a swing of 104 percentage points! Again, we must conclude that forgetting varies widely.
  4. Many of the experiments reviewed in this report showed clearly that learning methods matter. For example, in the Bahrick 1979 study, the best learning methods produced an average forgetting score of -29% forgetting, whereas the worst learning methods produced forgetting at 47%, a swing of 76% points. In Runquist’s 1983 study, the best learning method produced average forgetting at 34%, whereas all the other learning methods produced average forgetting of 78%. In Allen, Mahler, and Estes’ 1969 experiment, the learners given the best learning methods forgot an average of 2.3%, whereas the learners who got middling learning methods forgot an average of 14.3%, and learners given the worst learning methods forgot approximately 21.7%. The bottom line is that the learning methods we choose make all the difference!!

Check out the full report to learn more about the following:

  • What you should do as a learning professional (in light of these findings).
  • Whether the learning-curve notion still applies.
  • What wisdom each of the 14 research articles revealed.
  • The methodology used in the research.
  • The calculation of forgetting.

 

21 replies
  1. Dale Brethower
    Dale Brethower says:

    Will,
    Thanks for the article!
    I am getting very good at forgetting, making great progress during the couple of decades since I passed 50. One thing I remember: “How much do people forget?” is a bad question for trainers or educators. Your answer, “it varies” has been known by serious researchers for decades; it is worth reminding everyone.
    A better question is “What variables influence remembering what has been learned?”
    The short answer “the same variables that influence using what has been learned” might or might not be the entire story. There is a small amount of conflicting evidence but possibly research will show that the remainder of the story is also told by “the same variables that influence using.” In the meantime, focusing on the variables that influence remembering will be more useful to trainers, or their clients. Focusing on “what doesn’t work” is very different than focusing on “what works.:

  2. Thiagi
    Thiagi says:

    Great summary, Will.
    Has practical applications for learning professionals.
    How about writing a book on this topic, stressing the importance of training and learning strategies?

  3. Clare Elizabeth Carey
    Clare Elizabeth Carey says:

    Thanks, Will! What a great way to start the new year – focusing on research that we can use at work. Appreciate your WILL-ingness to share your sanity. Your suggestions are on point.

  4. Simone Sietsma
    Simone Sietsma says:

    This is an excellent piece. Thank you. Finally some real data to dispute those nebulous claims! Thank you for your generous approach to knowledge sharing.

  5. Brad Fallon
    Brad Fallon says:

    I think the reason that we forget is because our brain can only take so much of information. Beyond its capacity to retain, it forgets. And also we have this selective memory that we only want to retain good memories.

  6. Richard Presley
    Richard Presley says:

    Brad, I would agree with you up to a point. I would say that is time dependent. Over a lifetime, I don’t know that anyone has reached an upper limit of what the brain is able to take in apart from debilitating diseases. Our ability to both organize information into conceptual sets that not only retain new knowledge better, but also synthesize new knowledge from existing knowlege strongly implies unlimited learning capacity. The problem is, without time to organize those conceptual sets, our brain is unable to fight the firehose of information.

  7. steve
    steve says:

    The argument that “people forget most of what you tell them in the classroom” often ignores this key question:
    – was what you were telling them (usually to pass some written exam) actually important in the first place?
    Furthermore…
    – if information is not central to the behavior change and is present simply to provide input reference for a permutation, I would guess that this information would be better served in a reference or job aid.
    I’ve always felt that there were certain types of activities in the classroom that produced a covert inception. The types of embedding that you know are going to have some type of recall applicability when it comes to real performance. How often is a worker going to encounter a written test in their regular duties?
    It’s great that you’re teasing out these nuances. Loving it.

  8. Frank Meister
    Frank Meister says:

    Will,
    I enjoyed your summary of the available research on memory retention. You make the case for instructional designers and educators to re-evaluate their instructional practices and pedagogy.
    I did want to get your opinion on a fascinating story I recently saw on 60 Minutes about a small group of people that researchers have identified as having the ability to recall events that occurred in their life and beyond on specific dates, effectively remembering every day of their life. The link to the story is below.
    http://www.cbsnews.com/stories/2010/12/20/earlyshow/leisure/celebspot/main7167813.shtml

  9. PetCareRx Reviews
    PetCareRx Reviews says:

    ‘m not sure what to say about your close family, but the general folks you may see everyday or pal around with may forget cos they can’t see the pain, like you can see a cast on an arm, or a wheelchair, or cane, etc. Good luck to you!

  10. Testking VCP-410
    Testking VCP-410 says:

    I am just writing a text for a seminar that I attended and was already wondering about the new versions of Dales Cone. Since our library doesn’t own Dales original writing including the cone I was almost fooled by the forged new versions that you can find anywhere in the web. I almost believed it.

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