Forgetting curve: Ebbinghaus and a second hand book

 

The book spurred this young man to conduct his famous memory experiments leading to the discovery of the forgetting curve and the spacing effect. The young man was Hermann Ebbinghaus, the first psychologist to apply mathematics to the study of psychology and to scientifically describe the learning curve. The findings of his experiments were published in a book in 1885 which was later translated into English as Memory: A Contribution to Experimental Psychology. 

The Forgetting Curve

A young German once moved around in the streets of England and France after completing his PhD looking for tutoring opportunities to support himself. On a fine morning, he came across Gustav Fechner’s Elements of Psychophysics in a used bookstore in London. The book spurred this young man to conduct his famous memory experiments leading to the discovery of the forgetting curve and the spacing effect. The young man was Hermann Ebbinghaus, the first psychologist to apply mathematics to the study of psychology and to scientifically describe the learning curve. 

    The findings of his experiments were published in a book in 1885 which was later translated into English as Memory: A Contribution to Experimental Psychology. The book had an immediate impact on the psychologists of his time. It revolutionized the study of human memory and learning, and the effect was so immediate and overwhelming that thirty-two research papers based on experimental studies on memory and learning were published in the US alone in 1894. 

    The book also generated an interest in the burgeoning of mechanized devices for memory assistance. The book was described as “heroic” and “the single most brilliant investigation in the history of psychology” by the famous American philosopher and psychologist William James. Ebbinghaus’ studies were mentioned as the most remarkable undertaking in the subject of memory since Aristotle!

    Before the publication of Ebbinghaus’ work, memory-related studies were based on observational descriptions and speculation expressed by philosophers. A concept called pure description was used by Immanuel Kant, the great German philosopher, in the discussion of cognitive recognition and its components. Francis Bacon, an otherwise brilliant scientific mind, kept claiming that memory cannot be studied by simple observation of the rote recollection of a list of items memorized earlier. These perceptions about the study of human memory and learning continued even till the second half of the nineteenth century. 

    In opposition to this popularly held opinion in educational psychology in the period, Ebbinghaus demonstrated that empirical experimentations were possible even in the study of the higher mental processes. His experiments in memory involved the use of the so-called “nonsense syllables”. These syllables were trigrams containing a consonant-vowel-consonant combination without any semantic content. 

    Ebbinghaus meticulously worked on a comprehensive list of such syllables as DAX, BOK, and YAT. He left out semantically cognate trigrams like BOL and DOT. Since BOL sounds like “Ball” and DOT is already a word, they were not acceptable as nonsense syllables. The argument behind the creation of such semantically vacuum syllables was that learning could be affected by previous information and comprehension. It was argued that the human mind may impose meaning even on semantically empty syllables. For instance, a nonsense syllable like KOJ would be more nonsensical than a syllable such as PED, which has some meaning associations with the word “pedal”. 

    So, the syllables used by Ebbinghaus for the experiments had no prior cognitive associations, but they could be easily memorized. They were harder to retrieve by semantic associations. The comprehensive list of such semantically zero syllables created by Ebbinghaus contained 2300 items. He almost left no such syllables to be framed by anybody after him! 

    He used these syllables for laborious memorization sessions. First, random syllables were chosen and written down in a notebook. He would read out the syllables and try to recall them at the end of the exercise. He worked so hard on his experiments that one such exercise alone took him 15000 recitations to complete in one go! The most famous result of this laborious experiment was the understanding of the forgetting curve. 

    Ebbinghaus demonstrated through his studies that the sharpest dip in human memory is in the first twenty minutes of learning maintaining a similar significant decline in the first hour. The forgetting curve tends to level off after about one day proving that the human mind suffers an exponential loss of information in sync with time. 

    Ebbinghaus’s theory of the learning curve describes the pace at which the human mind learns new information. As per the learning curve, the first attempt at learning shows the sharpest increase in retention with a gradual decline in the curve with each repetition. Just like the forgetting curve, the learning curve is also exponential. Increased speed in the recall of the most recent information is possible because of its storage in short-term memory. Parallelly, an increased rehearsal in recalling the same information commits it to long-term memory. 

    The good thing about the human memory engaged in learning new information is that a fair amount of information is retained in the subconscious although it cannot be consciously accessed for immediate use. To understand this fact, Ebbinghaus would sit for hours and hours together memorizing a list of nonsense syllables till he could completely memorize them and draw a learning curve. Then he would wait till the day he could no longer recall a single syllable in the list. 

    He would memorize the syllables in the list once again and draw another learning curve. After comparing the two learning curves he found that the second learning curve showed a faster rate of retention than the first learning curve. Describing these functions as involuntary and voluntary memory, Ebbinghaus stated the first as spontaneous and non-volitional and the second as caused by a conscious “exertion of the will”. 

    One of the more curious speculations about Ebbinghaus is that none of his teachers and colleagues has been credited with any influence on his research on the foundation of remembering. Although his PhD dissertation was written in opposition to Von Hartmann’s opinion that the higher mental processes were situated beyond sensory observation, Ebbinghaus’ works on human memory and learning were unique and unprecedented. 

    One significant influence, however, had been repeatedly mentioned as the singular inspiration of Ebbinghaus’ research on human memory and that was Gustav Fechner’s Elements of Psychophysics. The famous second-hand book that Ebbinghaus purchased from a bookstore in London. Fechner’s book showed Ebbinghaus how mathematical rigour applied to the understanding of psychophysics could also be applied in educational psychology. Acknowledging the influence of Fechner’s ideas presented in that second-hand book, Ebbinghaus dedicated his Principles of Psychology, his second book on human memory and learning, to Fechner stating, 

    “I owe everything to you”. 

It is a wonderful feeling that worn-out second-hand books can also generate everlasting first-hand ideas!

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