How did Hermann Ebbinghaus conduct memory experiments on himself?

Question

I was reading about Hermann Ebbinghaus. He became interested in experimental psychology which led him to conduct memory experiments on himself which then resulted in the publication of his book: "Memory: A Contribution to Experimental Psychology" in 1885.

He discovered the forgetting curve and the spacing effect. How did he do so? I'm aware that he had a list of 2300 "nonsense syllables" to memorize but I have no idea what his process was like. Did he play with different intervals for the review of the material? Things like that. Is the process explained in the book?

I'd like to look at the details to see the connection between his work and the now available software employing spaced repetition algorithms.

Answer 1

Ebbinghouse indeed only tested on himself, limiting the generalization of his findings.

Your question is a really good one; given the time of his writing, the now so familiar structure of a standard journal paper (Abstract, Introduction, M&M, Results, Discussion) is not present in his monograph. However, tucked away in the text on p. 51 of 100 in this pdf version of his book he describes the following:

The investigations in question fell in the year 1879-80 and comprised 163 double tests. Each double test consisted in learning eight series of 13 syllables each [...] and then in relearning them after a definite time. The learning was continued until two errorless recitations of the series in question were possible. The relearning was carried to the same point; it occurred at one of the following times, -- namely, after about one third of an hour, after 1 hour, after 9 hours, one day, two days, six days, or 31 days.

As far as I understand, hence, he learned a sequence of syllables and then he basically tried to re-learn those sequences after a series of fixed times and see how his scores were the second time.