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.