Hermann Ebbinghaus published a landmark book in 1885, Uber das Gedachtis (On Memory), translated into English in 1913. In this he put the study of memory on a sure, scientific footing using rigorous experiments, exploring retention and the effects of sequencing and patterns of practice on memory. Indeed, most subsequent research into learning and memory has been footnotes to his work.
Decay from memory
In perhaps his most famous experiment, trying to remember syllable lists, he found that after certain periods he remembered only a percentage of the original: after 20 mins 58%, an hour 44%, 24 hours 34%, 31 days 21%. This was the ‘forgetting curve’. In other words, within a month, nearly 80% of the learned content had been lost. But the real lesson was that most of the loss came in the first few minutes. The distinction between short and long-term memory was made, and it became clear that successful learning had to push knowledge from short to long-term memory to be successful. Of course, it is not simply a matter of practice and reinforcement, related meaning and the organisation of the material are also important.
A less well known, but just as significant, discovery was the benefit of distributed or spaced practice. Distributed practice is spread out over a period of time, whereas massed practice takes place in one session. The spacing out of practice seems to avoid fatigue effects and lead to more consolidation of memory. Consolidation seems to be optimal after about 20 minutes, suggesting that we should practice and reinforce learning after 15-20 minutes. This flies in the face of most teaching and instruction, whether it be school lessons, lectures or ‘sheep-dip’ training courses. Much of what passes for learning experiences are therefore wasted, as reinforcement through spaced practice is neither planned nor executed.
Primacy and recency
Ebbinghaus also discovered the serial position effect. In remembering lists, he observed that people are far more likely to remember items at the start and end of lists. These effects are called primacy and regency. It depends on the nature of the material, the relationship between the material and users approach to learning, but by and large the principle is that material from both ends of a learning experience are retained more than the stuff in the middle. This has been confirmed many times since.
Take the example of the Presidents of the US. Most people remember Washington and the more recent Bush and Obama. Incidentally, many people also remember Abraham Lincoln, confirming another psychological effect in learning, the von Rector effect (1933). He found that the more something stands out from the crowd, the easier it is to remember. In a specific experiment by E.J Thomas in Studies in Adult Education (1972), it was found that there was a massive dip in attention and recall from the middle of lectures. In other words, in lectures and the classroom the effects of primacy and recency are profound. Primacy, and especially recency, have also opened up avenues of research, especially in providing clues for working hypotheses on how working memory operates.
Some argue that learning theory is fundamentally memory theory and if William James is the father of psychology, Ebbinghaus is the father of memory theory. He was the first, great experimental investigator into memory, and quickly saw that most learning leads to forgetting. The whole idea of forgetting is still all too absent in education and training with little attention given to reinforcement methods and spaced practice. Most of the major findings in this area were covered by him and many of his central conclusions remain intact and instructive. Although his investigations really only apply to relatively, simple, rote learning, he opened up avenues of inquiry that have led to astounding progress in the psychology of memory.
Ebbinghaus, Hermann (1885). Translation of Memory: A Contribution to Experimental Psychology