It turns out that forgetting is an essential part of learning.

When learners (or educators) talk about “teaching to the test” and “cramming,” they are describing massed learning—attempting to learn and remember a mass of information in a single session or a few closely spaced sessions. That “learning” is measured by the learners’ ability to recall that information on a test or other assessment given in the same context (classroom) and generally within a short time frame, such as a semester.

However, as many learners know only too well, after “cramming,” the learning doesn’t tend to stick. For long-term retention or solid learning that can be applied in contexts and to problems different from those posed in the study session, a different approach to learning is needed: spaced learning.

Spaced learning can be applied to both inductive learning, which emphasizes critical thinking, problem-solving, and analysis; and deductive learning, which presents rules and examples. It can enable the long-term recall of facts as well as deeper understanding of concepts. And it’s based, in part, on the mechanisms in the brain that help people remember some information while forgetting other information.

Ebbinghaus and the “forgetting curve”

Beginning in 1885, Dr. Hermann Ebbinghaus, a German psychologist, conducted a series of experiments on memory, using himself as a subject. He memorized lists of nonsense syllables and tested his recall of those syllables.

Some of his findings have morphed into a concept known as the “forgetting curve,” which relates to the effect of time and repetition on the ability to recall information. The forgetting curve shows the drop-off in recall over time following learning. The steepest part of the forgetting curve is immediate: Learners will forget up to half of new information within an hour or so of training; after a week, they’ll have forgotten nearly everything. But obviously, people do learn and retain information, so the curve is not the end of the story.

Forgetting is a key element of the learning process because it helps the brain sort important from trivial information; in this age of information overload, a filtering process is essential. “The ability to retrieve and generate information that is wanted, relevant, and appropriate is made possible by the ability to inhibit, and thus forget, information that is unwanted, irrelevant, and inappropriate,” according to researcher Benjamin Storm.  

Spaced learning or spaced retrieval practice can reshape the forgetting curve and help learners control which information is retained and which is discarded. When a person periodically practices reviewing information and retrieving that information—by solving problems, applying concepts, answering test questions, or using other forms of recall or assessment—it reinforces the learning. At the same time, information that is not recalled tends to fade from the learner’s memory. The intervals between repetitions or recall attempts can grow larger over time, as the learner’s memory of the information becomes stronger; the information eventually becomes part of learners’ long-term memories.

Other factors can influence learning and memory, of course: A strong emotion can cement memories of an event—like the September 11 attacks on the US World Trade Center or the assassination of President Kennedy in 1963—in people’s minds forever, including minute details, such as where they were or what they were wearing. But that type of emotional impact is rare and tough to plan. Educators seeking to make eLearning impactful and sticky can more easily apply the science underlying spaced learning to improve retention.

The goal: Long-term retention

Short-term recall—regurgitating information for a test—is rarely the goal of eLearning. Employers are looking for long-term retention of skills and knowledge that will lead to a boost in performance.

In an article published in Change, “Applying the Science of Learning to the University and Beyond,” as well as in a book and conference of the same name, Diane Halpern and Milton Hakel state that “the single most important variable in promoting long-term retention and transfer is ‘practice at retrieval.’ … Simply stated, information that is frequently retrieved becomes more retrievable.”

It’s a complex puzzle: “Principles of learning are difficult to discuss in isolation because learning activities that occur at different times—at the point of initial learning, during the retention interval, and at the point of recall—are all interdependent. They work together to determine what is remembered at some point in the future, well after the first recall test is administered. According to standard ‘memory trace’ theories of how we remember, the act of remembering strengthens some memory traces and weakens—or at least fails to strengthen—others,” according to Halpern and Hakel.

In addition, processing information in different formats and different contexts aids learning and retention, as does being asked to present information in a different way than it was learned, whether that is a different modality or applying it to a new problem. “When learning occurs under varied conditions, key ideas have ‘multiple retrieval cues’ and thus are more ‘available’ in memory,” according to Halpern and Hakel. And, they add, if educators or trainers are simply teaching to the test, lecture or presentation of information to passive learners might suffice, but “it is one of the worst arrangements for promoting in-depth understanding. … Understanding is an interpretive [emphasis in original] process in which students must be active participants.”

Spaced vs. massed learning

Interpretive, interactive learning, where learners take in and reproduce information in multiple formats and apply it to different contexts and problems, can easily be accomplished using spaced learning. And varying the information and context aids learning in other ways.

One reason that people learn and remember more during spaced practice might be that they pay more attention. Janet Metcalf and Judy Xu’s study (see References), which reproduced results of earlier research, explored that hypothesis. They compared massed and spaced learning to test inductive learning and to gauge the degree to which participants “mind wandered,” or let their focus drift from the task.

Metcalf and Xu describe a cycle of attention and learning, pointing to the psychological and behavioral concept of habituation: “It has long been known that stimulus repetition results in habituation, with the attendant loss of attention to the repeated stimulus.” In plain English, that means people stop paying attention to something that’s repeated—a sound, a scent, or a series of similar photos, for example.

The authors describe so-called “stop rules” in learning research that say people “stop studying when they have reached an internal criterion indicating that the item is sufficiently learned” or they “perceive that they are no longer taking in new information.” Either or both of these conditions could easily occur during “cramming” or massed learning, causing learners to “mind wander.”

Their study looked at participants’ ability to determine which artist created a work of art. Participants looked at multiple examples of the work of each of several artists. In the massed learning condition, many works by the same artist were presented in succession; each viewing session presented a different artist. In the spaced learning condition, participants viewed a mix of works of different artists within each viewing session. All participants were later asked to view images of different works from the same artists and to figure out which artist had created them.

Participants in the spaced learning condition reported less mind wandering than those in the massed condition. Their recall of the information was better than that of learners in the massed learning condition, and spaced learning led to a better ability to apply the information to a new problem—correctly identifying the artist who created works that they had not seen previously.

eLearning offers many opportunities for spaced learning and retrieval

The examples provided illustrate very different applications of spaced learning. The “spacing” can occur within a single session or by scheduling sessions several hours or days apart. Dr. Paul Kelley, a British neuroscientist, uses a format that separates sessions by only a few minutes, as described in “Buzzword Decoder: Spaced Learning.” Spacing can apply to time, content, or both.

But whatever paradigm is used, eLearning offers a variety of ways to implement spaced learning. Spaced learning is possible using a range of platforms and delivery methods, including virtual classrooms, desktop or mobile devices, and synchronous or asynchronous delivery.


Halpern, Diane F., and Milton D. Hakel. “Applying the Science of Learning to the University and Beyond: Teaching for Long-Term Retention and Transfer.” Change: The Magazine of Higher Learning, Vol. 35, No. 4. July/August 2003.

Hogle, Pamela. “Buzzword Decoder: Spaced Learning.” Learning Solutions Magazine. 8 November 2016.

Metcalfe, Janet, and Judy Xu. “People Mind Wander More During Massed Than Spaced Inductive Learning.” Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 42, No. 6. June 2016.

Storm, Benjamin C. “The Benefit of Forgetting in Thinking and Remembering.” Current Directions in Psychological Science, Vol. 20, No. 5. October 2011.