Overview of the Ebbinghaus Forgetting Curve

Hermann Ebbinghaus (January 24, 1850 – February 26, 1909), a German psychologist and the founder of experimental learning psychology, discovered through his research that forgetting begins immediately after learning, and that the process of forgetting is not uniform: the rate of forgetting is rapid at first and gradually slows down. He believed that “retention and forgetting are functions of time” and, based on his experimental results, plotted a curve describing the forgetting process—the famous Ebbinghaus Forgetting Curve.

In 1885, he published his experimental report, which demonstrated that information input into the human brain, after being processed through the learning process of attention, becomes short-term memory. However, if not reviewed promptly, these remembered items will be forgotten; conversely, with timely review, this short-term memory transforms into long-term memory, thereby remaining in the brain for a long time. So, for us, what exactly constitutes forgetting? Forgetting refers to the inability to recognize or recall something we once remembered, or to recognize or recall it incorrectly; all of these constitute forgetting. When Ebbinghaus conducted this experiment, he used himself as the test subject and drew several conclusions about memory. He selected syllables that were completely meaningless—that is, combinations of letters that could not form words, such as asww, cfhhj, ijikmb, rfyjbc, and so on.
 

Different types of material follow different forgetting curves. 

In his experiments on memory, Ebbinghaus found that memorizing 12 meaningless syllables required an average of 16.5 repetitions; memorizing 36 meaningless syllables required 54 repetitions; yet memorizing the 480 syllables in six poems required only 8 repetitions on average! This experiment shows us that knowledge we understand can be remembered quickly, comprehensively, and firmly. Otherwise, simply memorizing by rote is a thankless task. Therefore, meaningful material is easier to memorize, while meaningless material requires more effort to memorize and is also difficult to recall later. Thus, the Ebbinghaus forgetting curve is a curve describing the process of forgetting, specifically for meaningless syllables. When comparing it to other types of material, Ebbinghaus derived different forgetting curves for materials of varying nature, though they are generally consistent.

Therefore, Ebbinghaus’s experiment fully confirms a fundamental principle: learning requires diligent review, and the better one understands the material, the slower the forgetting process.

Personalized Ebbinghaus Forgetting Curve

　　The Ebbinghaus Memory Curve is a graphical representation derived from extensive laboratory testing conducted by Ebbinghaus, which yielded diverse memory data and ultimately established a universal pattern. This curve does not account for the individual characteristics of the test subjects but rather seeks to identify a balanced pattern of memory retention. However, memory patterns can be tailored to each of us, as our physiological traits and life experiences differ, potentially leading to distinct memory habits, methods, and characteristics. For individuals seeking to shape the world, these general principles can only serve as a catalyst. If they align with a person’s unique memory characteristics, learning becomes effortless and rapid; if they conflict with those characteristics, the effectiveness of memory retention is significantly diminished. Therefore, we must identify our own personalized Ebbinghaus memory curve based on our individual traits.

Conclusions of the Ebbinghaus Forgetting Curve

Memory is a complex psychological process influenced by many factors. Traditional associationists merely inferred causes from effects without providing scientific explanations; Ebbinghaus, however, observed outcomes by strictly controlling variables and conducted a quantitative analysis of the memory process.

First, he noted that memorized material varies in length, difficulty, and familiarity, and must be strictly controlled. To eliminate the influence of prior experience on memorization and ensure that the material was of equal difficulty, he created a set of meaningless syllables.

Second, he strictly controlled all conditions that affect memorization outcomes, including study duration, number of repetitions, memorization intervals, and memorization methods. As for subjective conditions, Ebbinghaus used himself as a subject, striving to standardize his daily life to ensure consistency in these factors. In this way, Ebbinghaus began by controlling the factors influencing memorization and used the method of economizing to conduct a quantitative analysis of various aspects of memory. Through years of patient and meticulous experimental research, he arrived at the following main conclusions:

(1) The relationship between the length of syllable groups and learning speed: As the length of syllable groups increases, the number of repetitions required to achieve accurate recall rises sharply. For example, memorizing 12 syllables requires only 16.6 repetitions, whereas memorizing 36 syllables requires 55 repetitions.

(2) The impact of material meaningfulness on learning: Ebbinghaus discovered that learning meaningful material is much faster than learning meaningless material. Ebbinghaus designed several experiments to determine the effects of various conditions on learning and retention. One of these studies aimed to identify the difference in memorization speed between meaningless syllables and meaningful material. To determine this difference, he memorized passages from Byron’s poem *Don Juan*, each consisting of 80 syllables, and found that it took approximately 9 readings to memorize a passage. He then memorized 80 meaningless syllables and found that this task required nearly 80 repetitions. He concluded that learning meaningless material is nearly nine times more difficult than learning meaningful material.

(3) The relationship between memory retention and the number of repetitions: The more repetitions and the longer the duration, the longer the memory is retained.

(4) The relationship between retention, forgetting, and time: The longer the time elapsed since learning, the less is retained and the more is forgotten; however, the rate of forgetting is not uniform. The curve derived from the data obtained in Ebbinghaus’s experiments is known as the Ebbinghaus forgetting curve.

(5) Spaced learning is superior to massed learning. For example, massed learning of a 12-syllable sequence requires 68 repetitions to achieve accurate recitation, whereas spaced learning requires only 35 repetitions.

(6) The relationship between the order of items within a syllable sequence and memory retention. This refers to his experiments on contiguous association, remote association, sequential association, and reverse association. He believed that through learning, not only adjacent syllables but also distant syllables can form associations; associations between syllables can be formed not only in sequence but also in reverse order. However, in terms of retention, adjacent syllables within a syllable group are retained better than distant or reverse-order syllables.

Ebbinghaus’s research on memory had a profound impact on psychology. It not only enriched the field of experimental psychology but also sparked a wave of research on memory among psychologists worldwide, greatly advancing the development of the psychology of memory. The findings of Ebbinghaus’s research on memory have had a lasting impact on psychology. Following his work, many scholars conducted confirmatory studies of his conclusions and arrived at the same results. In a sense, modern psychological research on memory still builds upon Ebbinghaus’s work, and much of the content on memory in today’s psychology textbooks remains based on his findings. Of course, like any new development, his research was not without flaws. Its main shortcomings include the following three points: First, he conducted only quantitative analyses of the development of the memory process, without analyzing changes in the nature of the memory content; second, the meaningless syllables he used were artificial and detached from reality, presenting significant limitations; and third, he treated memory as the result of mechanical repetition, failing to consider that memory is a complex, active process.

Quantitative Research on the Ebbinghaus Forgetting Curve

At the 1999 World Congress of Memory Science in the United States, a study titled “Quantitative Research on the Ebbinghaus Forgetting Curve” was presented. The findings revealed that during the human memory process, three types of memory are formed within a specific timeframe: sensory memory, short-term memory, and associative memory.

Consider a memory event—let’s take the example of memorizing a word. When this event occurs, a “sensory memory” forms within a few seconds. This sensory memory is fleeting and varies from person to person, but generally lasts no more than 3 or 4 seconds. It doesn’t feel particularly vivid when memorizing a word, but when does it become vivid? Following the sensory memory, a “short-term memory”—also known as “working memory”—emerges. The duration of this memory also varies, generally lasting between 4 and 16 hours—a fourfold difference among individuals. When is this used? For example: During a break, a teacher tells students, “We’ll have a spelling test on the words we learned yesterday in the next class.” You feel particularly anxious, so you rush to memorize them after class. Does it work? It does! But after school, once you’ve had a meal or played for a while, you can’t remember a thing. This is short-term memory—it vanishes immediately after memorization. During the process of these two types of memory fading, a long-term memory trace is formed. This is what we care about most and what is most useful—your true memory. Whether you’re learning a word or anything else, you rely on this long-term memory trace. It follows a parabolic curve, reaching a peak—the highest point. This is the strongest point of your memory for that word, the peak of the memory formed during this learning session. This peak generates a specific level of memory strength and also defines a specific time frame. During a certain period, your memory of the word will reach its strongest point. Simply put, if someone can identify this point and conduct a second round of intensive review at that moment, it is the most effective approach. When we flip through books or look at flashcards, we are essentially simulating this “T”—the repetition interval—which is the golden sequence of memory formed by the arrangement of each forgetting point. At the 1999 World Memory Championship, this "T" was finally identified; scientists discovered it through human-computer interaction.

Since everyone’s memory curve is unique, their forgetting points (which are also optimal memory points) vary accordingly. The Memory Core System uses simple human-computer interaction to identify a learner’s forgetting points using the human brain’s “golden sequence” method. It then gradually adjusts to a golden sequence tailored to the learner’s specific circumstances. As the study time approaches the learner’s forgetting point, it repeats content that has not yet been consolidated into long-term memory, determining the frequency and number of times English words appear, until the forgetting point disappears, thereby achieving lifelong memory akin to that of a native speaker.