“The Conditions of Retention”, 1922 (; backlinks):
The problem of the present study is to investigate the nature of the curve of retention under certain variable conditions. The experiments were performed in the Psychological Laboratory of the University of Chicago, the first series from May to August 1919, and the second from October 1919, to February 1920.
Series of nonsense syllables of 12 each were used. With the English alphabet, a list was made of all possible combinations of two consonants joined by a vowel in the middle, except those which end in y. The apparatus was an ordinary rotating drum used in the Chicago laboratory for most of the memory experiments. After the series were typewritten on strips of white manila card, they could be easily fixed to the drum. The subject was seated at a convenient distance in front of the rotating drum.
Before the presentation of every new series, the experimenter gave the signal “ready, —” one second after which the first syllable was exposed. Apparently the Chinese students had no serious difficulty in learning this type of material. They were able to memorize directly without translating the exposed material into Chinese equivalents. On the whole, they learned the series very much faster than did the Americans.
The curve of retention varies with the degree of the original learning. The amount of retention for most intervals increases with the degree of learning. Differing from the Ebbinghaus tradition, our curves are not all logarithmic. Some of the recognition curves do not even manifest the phenomenon of negative acceleration in general.
[1929 summary: “The subjects, college students and one instructor, memorized series of nonsense syllables of 12 each. The lists were presented on a memory drum, each word being exposed for two seconds. Only one degree of overlearning was used, namely 150% learning. The intervals between learning and recall were 4 hours, 1 day and 2 days. Retention was tested by the methods of unaided written reproduction, recognition and reconstruction. The increase of retention was always less than the degree of overlearning. The ratio of retentive increase to the degree of overlearning decreased with the interval, and in some cases overlearning even proved detrimental. For example, when retention was measured by written reproduction, the 4-hour interval showed an increase of 17.1%, while the 1-day interval gave an actual decrease of 7.1%, and the 2-day interval showed a decrease of 10.6%. The results were the same for all 3 methods of measuring retention.”]
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