The forgetting curve: the science of how fast we forget

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We spend a lot of time reading and studying in the hope of acquiring new knowledge. However, most of us focus a lot more on learning rather than remembering. As a result, our mind is often a leaky bucket we keep on trying to fill, only for all of that new knowledge to soon disappear. This is because knowledge does not only have a learning curve. It also has a forgetting curve.

The Ebbinghaus forgetting curve

Hermann Ebbinghaus was a German psychologist who is known as a pioneer in the experimental study of memory. Curious about why we forget things and how to prevent it, he decided to run a study on himself. From 1880 to 1885, Ebbinghaus tried to commit words to memory, and repeatedly tested himself after various time periods, and recorded the results. The words were nonsense combinations of syllables, following a Consonant–Vowel–Consonant pattern. He then plotted the results he obtained on a graph, which looked like this:

Ebbinghaus Forgetting Curve

This graph is now known as the forgetting curve, which illustrates how information we learn is lost over time when we make no attempt to retain it. The forgetting curve suggests that we tend to halve our memory of new knowledge in a matter of days or weeks, unless we make a conscious effort to review the newly learned material.

Of course, such a study with just one subject is limited in nature, but Ebbinghaus is considered one of the first scientists to explore the subject of forgetting through well-designed experiments on the subject of forgetting, and his research contributed a lot to the field of experimental psychology.

In fact, Ebbinghaus’ findings are interesting enough for scientists to still explore the concept of the forgetting curve to this day. As you may know, psychology is a field where replication of studies is often a problem. However, in 2015, a research team successfully reproduced the forgetting curve from Ebbinghaus’ findings.

The researchers write: “In 1880, Ebbinghaus set new standards for psychology experiments, already incorporating such ‘modern’ concepts as controlled stimulus materials, counterbalancing of time-of-day effects, guarding against optional stopping, statistical data analysis, and modeling to find a concise mathematical description and further verify his results. The result was a high-quality forgetting curve that has rightfully remained a classic in the field. Replications, including ours, testify to the soundness of his results.”

Knowing that you will probably forget most of what you study in the absence of intentional attempts to retain information, how can you go about reducing your forgetting rate so you can remember more of what you learn?

How to reduce your forgetting rate

Be honest: how often have you read a book only to forget most of its content a few months later? How much do you remember of that article you thoroughly enjoyed reading last year? When people ask you what a podcast episode you recommended is about, are you able to give them a detailed summary, or only share a vague overview?

Most people have a high forgetting rate. The good news is, Ebbinghaus explored some ways to reduce that rate so your forgetting curve is not so steep.

  1. Build meaningful memories. The better you understand the information you want to remember, the easier it will be to recall that information. Ebbinghaus suggests fostering better memory representation by using mnemonic techniques, which are structured strategies to better memorise and remember things. The concept of mnemonic techniques is not new: as it was essential for orators to remember what they had to say when addressing a crowd, these techniques were already used by ancient Greeks and Romans to practice what they called the “Art of Memory”. They are still employed nowadays by memory champions.
  2. Use spaced repetition. Ebbinghaus found that repetition based on active recall, and especially spaced repetition, was practically helpful in reducing his forgetting rate. This is because of the spacing effect, which shows that much more information is encoded into your long-term memory — and better — when you avoid cramming everything you want to learn in one study session (which researchers call “mass practice”), and use spaced study sessions instead. The spacing effect has been extensively studied and is one of the few evidence-based learning strategies you can confidently rely on.
  3. Practice overlearning. Lastly, Ebbinghaus defined overlearning as the number of repetitions of information after which it can be recalled with perfect accuracy. Overlearning consists in reviewing newly acquired knowledge beyond the initial point of mastery. In a 1992 meta-analysis, researchers found that overlearning may indeed significantly affect recall over time. However, recent research suggests that the effects of overlearning tend to not last very long, so take this one with a grain of salt.

Keep in mind that, even though a lot of Ebbinghaus’ work has been reproduced, his own sample size was just himself and he used a very specific type of content to remember. Many differences in context, content, and individual abilities will impact the way we learn and remember. The forgetting curve should not be interpreted as a general graph that can be applied to everyone. Rather, it is an illustration of how we tend to rapidly forget the information we study if we don’t use it nor make any attempt to retain it.

There is no magic bullet to easily recall everything you learn about. Knowledge needs to be understood, then regularly used in order for you to remember it. This requires a conscious effort and a higher time commitment than just consuming content without any attempt to retain it. As such, be selective with what you want to remember, and make it as simple as possible by using the right tools.