Hermann Ebbinghaus, a German psychologist working in the late 19th century, is a foundational figure in the scientific study of human memory. His work marked a significant turning point, moving the investigation of complex mental processes away from philosophical speculation and toward objective, measurable experimentation. Ebbinghaus applied rigorous, quantitative methods to understand how we learn and forget information. His findings, detailed in his 1885 publication Über das Gedächtnis (On Memory), laid the groundwork for modern memory research.
The Experimental Pioneer
Before Ebbinghaus, memory was studied through philosophical introspection and subjective self-reports, often considered unsuitable for empirical science. Ebbinghaus initiated a methodological revolution by asserting that higher mental processes, like memory, could be studied using objective, controlled techniques, similar to those applied to sensory perception (psychophysics).
He served as both the experimenter and the sole subject for his systematic investigations, allowing for meticulous control over variables. Ebbinghaus documented his processes, including the timing of learning sessions and recall intervals. His commitment to measurement and mathematical analysis transformed the study of memory into a legitimate subfield of experimental psychology.
The Creation of Nonsense Syllables
A major challenge for Ebbinghaus was isolating pure memory formation from pre-existing knowledge or emotional bias. To overcome this, he invented the nonsense syllable: a three-letter unit following a consonant-vowel-consonant (CVC) structure, such as “KEP” or “ZOF.” He generated a pool of approximately 2,300 syllables that had no inherent meaning in German.
This innovation created material that was uniformly new and lacked prior association for the learner. By memorizing long lists of these meaningless trigrams, Ebbinghaus could measure the effort required for initial memory trace formation without the confounding effect of familiarity. He read these lists aloud at a steady pace until he could recite them perfectly.
Defining the Forgetting Curve
Ebbinghaus is most directly associated with the forgetting curve, a mathematical description of the rate at which memory decays over time when information is not actively reinforced. His experiments demonstrated that the loss of newly acquired information is neither linear nor gradual. The curve shows a rapid initial decline in retention immediately following the learning period.
He observed that a significant portion of information could be forgotten within the first hour, with the rate of loss slowing down considerably thereafter. For instance, 50 to 70 percent of the material could be forgotten within 24 hours without review. After this steep initial drop, the curve flattens out, indicating that the remaining memory trace is more stable and subject to a much slower rate of decay. This quantifiable pattern provided the first empirical evidence that forgetting is an orderly and predictable process, rather than a random event.
Measuring Memory Through Relearning
While the forgetting curve shows how much information is lost, Ebbinghaus developed the Savings Method (or Relearning Method) to measure how much memory is retained. This method is based on the idea that a residual memory trace exists even when material cannot be consciously recalled.
The “savings” are calculated by determining the difference in time or repetitions required to relearn a forgotten list compared to the original learning time. For example, if a list took twenty minutes to memorize initially but only ten minutes to relearn a week later, the savings are fifty percent. This reduction in effort quantifies the residual strength of the memory. The Savings Method established that memory retention is not an all-or-nothing phenomenon. It demonstrated that the effort saved during re-acquisition is a sensitive measure of the subconscious memory trace, quantifying the persistence of memory beyond conscious recall.