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Happened to notice these two statements printed in vendor literature at a recent conference. I’ve obscured their names just enough so I’m not obviously picking on them but they will know who they are.

Statement #1 from vendor named “C*g*i*o”

  • “We all know that up to 80% of what learners are taught in training will be lost in 30 days if there is no practice or reinforcement.”

Statement #2: from vendor named “A*ea*”

  • “We have known for more than 150 years that humans forget up to 70% of what they learn within 24 hours!”

These statements are false and misleading. To get a more accurate view of human forgetting, check out this well-researched document.

The Sad Reality of Faux or Misleading Research Citations in Vendor Literature

Buyer beware! Vendors are now utilizing confirmatory-bias methodologies to sprinkle their verbal and visual communications with research-sounding sound bites. Because we are human, this persuasion technique is likely to snare us.

We may even buy a product or service that doesn’t work.

My recommendation: Spend $500 on a research-to-practice expert to save yourself tens or hundreds of thousands of dollars, euros, pounds, etc.

 

 

For millennium, scholars and thinkers of all sorts — from scientists to men or women on the street — thought that memories simply faded with time.

Locke said:

"The memory of some men, it is true, is very tenacious, even to a miracle; but yet there seems to be a constant decay of all our ideas, even of those which are struck deepest, and in the minds of the most retentive; so that if they be not sometimes renewed by repeated exercise of the senses, or reflection on those kinds of objects which at first occasioned them, the print wears out, and at last there remains nothing to be seen."  John Locke quoted by William James in Principles of Psychology (p. 445, the 1952 Great Books edition, original 1891).

However, in the mid 1900's research by McGeoch (1932), Underwood (1957) and others found that memories can fade when what is learned interferes with other things learned. Previous things learned can interfere with current learning (proactive interference) and current learning can be interfered with by subsequent learning (retroactive interference).

The debate between decay and interference went on for over a century! Indeed, it paralleled the debate in physics over the property of light. Is it a wave or a particle?

The first ever photograph of light as both a particle and wave

In physics, the debate was so important that Albert Einstein won the Nobel Prize for the solution. Einstein's solution was simple. Light was BOTH a wave and a particle. The picture above is reported by Phys.org to be the first photograph demonstrating light's dual properties.

Now in the psychological research, we have the first experimental evidence that forgetting may be caused by BOTH decay and interference.

In a clever experiment, published just this month, Talya Sadeh, Jason Ozubko, Gordon Winocur, and Morris Moscovitch found evidence for both interference and decay.

Their research appears to be inspired, at least partially, by neuroscience findings. Here's what the authors say:

"Two approaches have guided current thinking regarding the functional distinction between hippocampal and extrahippocampal memories. The first approach maintains that the hippocampus supports a mnemonic process termed recollection, whereas extrahippocampal structures, especially the perirhinal cortex, support a process termed familiarity… Recollection is a mnemonic process that involves reinstatement of memory traces within the context in which they were formed. Familiarity is a mnemonic process that manifests itself in the feeling that a studied item has been experienced, but without reinstating the original context." (p. 2)

To be clear, this was NOT a neuroscience experiment. They did not measure brain activity in any way. They measured behavioral findings only.

In their experiment, they had people engage in a word-recognition task and then gave them either (1) another word-learning task, (2) a short music task, or (3) a long music task. The first group's word-learning task was designed to create the most interference. The longer music task was designed to create the most decay (because it took longer).

The results of the experiment were consistent with the researcher's hypotheses. They claimed to have found evidence for both decay and interference.

Caveats

Every scientific experiment has caveats. Usually these are pointed out by the researchers themselves. Often, it takes an outside set of eyes to provide caveats.

Did the researchers prove, beyond the shadow of a doubt, that forgetting has two causes? Short answer: No! Did they produce some interesting findings? Maybe!

My big worry from a research-design perspective is that their manipulation distinguishing between recollection and familiarity is somewhat dubious, seemingly splitting hairs in the questions they ask the learners. My big worry from a practical learning-design perspective is that they are using words as learning materials. First, most important learning situations utilize more complicated materials. Second, words are associative by their very nature — thus more likely to react to interference than typical learning materials. Third, the final "test" of learning was a recognition-memory task that involved learners determining whether they remembered seeing the words before — again, not very relevant to practical learning situations.

Practical Ramifications for Learning Professionals

Since there are potential experimental-design issues, particularly from a practical standpoint, it would be an extremely dubious enterprise to draw practical ramifications. Let me be dubious then (because it's fun, not because it's wise). If the researchers are correct, that memories that are context-based are less likely to be subject to interference effects; we might want to follow the general recommendation — often made today by research-focused learning experts — to provide learners with realistic practice using stimuli that have contextual relevance. In short, teach "if situation–then action" rather than teaching isolated concepts. Of course, we didn't need this experiment to tell us that. There is a ton of relevant research to back this up. For example, see The Decisive Dozen research review.

Beyond the experimental results, the concepts of delay and interference are intriguing in and of themselves. We know people tend to slide down a forgetting curve. Perhaps from interference, perhaps from decay. Indeed, as the authors say, "it is important to note that interference and decay are inherently confounded."

Research

The experiment:

Sadeh, T., Ozubko, J. D., Winocur, G., & Moscovitch. M. (2016) Forgetting patterns differentiate between two forms of memory representation. Psychological Science OnlineFirst, published on May 6, 2016 as doi:10.1177/0956797616638307.

The research review:

Sadeh, T., Ozubko, J. D., Winocur, G., & Moscovitch, M. (2014). How we forget may depend on how we remember. Trends in Cognitive Sciences, 18, 26–36.

 

 

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.