• Psychologist Hermann Ebbinghaus, 1850
  

After acquiring his Ph.D., Ebbinghaus moved around England and France, tutoring students to support himself. In England, he may have taught in two small schools in the South of the country. In London, in a used bookstore, he came across Gustav Fechner's book Elemente der Psychophysik (Elements of Psychophysics), which spurred him to conduct his famous memory experiments. After beginning his studies at the University of Berlin, he founded the 3rd psychological testing lab in Germany (3rd to Wilhelm Wundt and G.E. Muller). He began his memory studies here in 1879. In 1885, the same year that he published his monumental work, Memory: A Contribution to Experimental Psychology, he was made a professor at the University of Berlin, most likely in recognition of this publication. In 1890, along with Arthur Konig, he founded the Psychological journal Zeitschrift für Physiologie und Psychologie der Sinnesorgane (The Psychology and Physiology of the Sense Organs).

In 1894, he was passed over for promotion to professor at Berlin, most likely due to his lack of publications. Instead, Carl Stumpf received the promotion. As a result of this, Ebbinghaus left to join the University of Breslau (now Wrocław, Poland), in a chair left open by Theodor Lipps (who took over Stumpf's position when he moved to Berlin). While in Breslau, he worked on a commission that studied how children's mental ability declined during the school day. While the specifics on how these mental abilities were measured have been lost, the successes achieved by the commission laid the groundwork for future intelligence testing. At Breslau, he again founded a psychological testing laboratory.

In 1902, Ebbinghaus published his next piece of writing entitled Die Grundzuge der Psychologie (Fundamentals of Psychology). It was an instant success and continued to be long after his death. In 1904, he moved to Halle where he spent the last few years of his life. His last published work, Abriss der Psychologie (Outline of Psychology) was published six years later, in 1908. This, too, continued to be a success, being re-released in eight different editions. Shortly after this publication, on February 26th 1909, Ebbinghaus developed pneumonia and died, at the young age of 60.

Ebbinghaus was determined to show that higher mental processes could actually be studied using experimentation, which was in opposition to the popularly held view of the time. To control for most potentially confounding variables, Ebbinghaus wanted to use simple acoustic encoding and maintenance rehearsal for which a list of words could have been used. As learning would be affected by prior knowledge and understanding, he needed something that could be easily memorized but which had no prior cognitive associations. Easily formable associations with regular words would interfere with his results, so he used items that would later be called “nonsense syllables” (also known as the CVC trigram). A nonsense syllable is a consonant - vowel - consonant combination, where the consonant does not repeat and the syllable does not have prior meaning. BOL (sounds like ‘Ball’) and DOT (already a word) would then not be allowed. However, syllables such as DAX, BOK, and YAT would all be acceptable (though Ebbinghaus left no examples) . After eliminating the meaning - laden syllables, Ebbinghaus ended up with 2,300 resultant syllables. Once he had created his collection of syllables, he would pull out a number of random syllables from a box and then write them down in a notebook. Then, to the regular sound of a metronome, and with the same voice inflection, he would read out the syllables, and attempt to recall them at the end of the procedure. One investigation alone required 15,000 recitations.

It was later determined that humans impose meaning even on nonsense syllables to make them more meaningful. The nonsense syllable PED (which is the first three letters of the word ‘pedal’) turns out to be less nonsensical than a syllable such as KOJ; the syllables are said to differ in association value. It appears that Ebbinghaus recognized this, and only referred to the strings of syllables as “nonsense” in that the syllables might less likely have a specific meaning and that no attempt to make associations with them for easier retrieval.

There are several limitations to his work on memory. The most important one was that Ebbinghaus was the only subject in his study. This limited the study’s generalizability to the population. Although he attempted to regulate his daily routine to maintain more control over his results, his decision to avoid the use of participants sacrificed the external validity of the study despite sound internal validity. In addition, although he tried to account for his personal influences, there is an inherent bias when someone serves as researcher as well as participant. Also, Ebbinghaus' memory research halted research in other, more complex matters of memory such as semantic and procedural memory and mnemonics

In 1885, he published his groundbreaking Über das Gedächtnis ("On Memory", later translated to English as Memory. A Contribution to Experimental Psychology) in which he described experiments he conducted on himself to describe the processes of learning and forgetting.

Ebbinghaus made several findings that are still relevant and supported to this day. First, arguably his most famous finding, the forgetting curve. The forgetting curve describes the exponential loss of information that one has learned. The sharpest decline occurs in the first twenty minutes and the decay is significant through the first hour. The curve levels off after about one day.

The learning curve described by Ebbinghaus refers to how fast one learns information. The sharpest increase occurs after the first try and gradually evens out, meaning that less and less new information is retained after each repetition. Like the forgetting curve, the learning curve is exponential. Ebbinghaus had also documented the serial position effect, which describes how the position of an item affects recall. The two main concepts in the serial position effect are recency and primacy. The recency effect describes the increased recall of the most recent information because it is still in the short - term memory. The primacy effect better memory of the first items in a list due to increased rehearsal and commitment to long - term memory.

Another important discovery is that of savings. This refers to the amount of information retained in the subconscious even after this information cannot be consciously accessed. Ebbinghaus would memorize a list of items until perfect recall and then would not access the list until he could no longer recall any of its items. He then would relearn the list, and compare the new learning curve to the learning curve of his previous memorization of the list. The second list was generally memorized faster, and this difference between the two learning curves is what Ebbinghaus called “savings”. Ebbinghaus also described the difference between involuntary and voluntary memory, the former occurring “with apparent spontaneity and without any act of the will” and the latter being brought “into consciousness by an exertion of the will”.

Prior to Ebbinghaus, most contributions to the study of memory were undertaken by philosophers and centered on observational description and speculation. For example, Immanuel Kant used pure description to discuss recognition and its components and Sir Francis Bacon claimed that the simple observation of the rote recollection of a previously learned list was “no use to the art” of memory. This dichotomy between descriptive and experimental study of memory would resonate later in Ebbinghaus’s life, particularly in his public argument with former colleague Wilhelm Dilthey. However, more than a century before Ebbinghaus, Johann Andreas Segner invented the “Segner - wheel” to see the length of after - images by seeing how fast a wheel with a hot coal attached had to move for the red ember circle from the coal to appear complete (iconic memory).

Ebbinghaus’s effect on memory research was almost immediate. With very few works published on memory in the previous two millennia, Ebbinghaus’s works spurred memory research in the United States in the 1890s, with 32 papers published in 1894 alone. This research was coupled with the growing development of mechanized mnemometers, or devices that aided in the recording and study of memory.

The reaction to his work in his day was mostly positive. Noted psychologist William James called the studies “heroic” and said that they were “the single most brilliant investigation in the history of psychology”. Edward B. Titchener also mentioned that the studies were the greatest undertaking in the topic of memory since Aristotle.

Ebbinghaus can also be credited with pioneering sentence completion exercises, which he developed in studying the abilities of schoolchildren. It were these same exercises that Alfred Binet had borrowed and incorporated into the Binet - Simon intelligence scale. Sentence completion had since then also been used extensively in memory research, especially in tapping into measures of implicit memory, and also has been used in psychotherapy as a tool to help tap into the motivations and drives of the patient. He had also influenced Charlotte Buhler, who along with Lev Vygotsky and others went on to study language meaning and society.

Ebbinghaus is also credited with discovering an optical illusion now known after its discoverer, the Ebbinghaus illusion, which is an illusion of relative size perception. In the best known version of this illusion, two circles of identical size are placed near to each other and one is surrounded by large circles while the other is surrounded by small circles; the first central circle then appears smaller than the second central circle. This illusion is now used extensively in research in cognitive psychology, to find out more about the various perception pathways in our brain.

Ebbinghaus is also largely credited with drafting the first standard research report. In his paper on memory, Ebbinghaus arranged his research into four sections: the introduction, the methods, the results, and a discussion section. This clarity and organization of this format was so impressive to contemporaries that it has now become standard in the discipline and all research reports follow the same standards laid out by Ebbinghaus.

Unlike notable contemporaries like Titchener and James, Ebbinghaus did not promote any specific school of psychology nor was he known for extensive lifetime research, having only done three works. He had never attempted to bestow upon himself the title of the pioneer of experimental psychology, did not seek to have any “disciples”, and left the exploitation of the new field to others.

In addition to pioneering experimental psychology, Ebbinghaus was also a strong defender of this direction of the new science, as is illustrated by his public dispute with University of Berlin colleague, Wilhelm Dilthey. Shortly after Ebbinghaus left Berlin in 1893, Dilthey published a paper extolling the virtues of descriptive psychology, and condemning experimental psychology as boring, claiming that the mind was too complex, and that introspection was the desired method of studying the mind. The debate at the time had been primarily whether psychology should aim to explain or understand the mind and whether it belonged to the natural or human sciences. Many had seen Dilthey’s work as an outright attack on experimental psychology, Ebbinghaus included, and he responded to Dilthey with a personal letter and also a long scathing public article. Among his counterarguments against Dilthey he mentioned that it is inevitable for psychology to do hypothetical work and that the kind of psychology that Dilthey was attacking was the one that existed before Ebbinghaus’s “experimental revolution”. Charlotte Buhler echoed his words some forty years later, stating that people like Ebbinghaus "buried the old psychology in the 1890’s". Ebbinghaus explained his scathing review by saying that he could not believe that Dilthey was advocating the status quo of structuralists like Wilhelm Wundt and Titchener and attempting to stifle psychology’s progress.

Some contemporary texts still describe Ebbinghaus as a philosopher rather than a psychologist and he had also spent his life as a professor of philosophy. However, Ebbinghaus himself would probably describe himself as a psychologist considering that he fought to have psychology viewed as a separate discipline from philosophy.

There has been some speculation as to what influenced Ebbinghaus in his undertakings. None of his professors seem to have influenced him, nor are there suggestions that his colleagues affected him. Von Hartmann’s work, on which Ebbinghaus based his doctorate, did suggest that higher mental processes were hidden from view, which may have spurred Ebbinghaus to attempt to prove otherwise. The one influence that has always been cited as having inspired Ebbinghaus was Fechner's Elements of Psychophysics, a book which he purchased second hand in England. It is said that the meticulous mathematical procedures impressed Ebbinghaus so much that he wanted to do for psychology what Fechner had done for psychophysics. This inspiration is also evident in that Ebbinghaus dedicated his second work Principles of Psychology to Fechner, signing it “I owe everything to you”.