Tolman, E. C. (1923). The Effects of Underlearning upon Short- and Long-Time Retentions. Journal of Experimental Psychology, 6(6), 466-474.
http://dx.doi.org/10.1037/h0072219
The author describes a new form of memory-apparatus by means of which the O himself controls the exposure of the second member of pairs of nonsense syllables. As the O exposes the syllable, a mark is made on a piece of paper so that at the end of a series the O has a record of the number of repetitions required for learning. The writer then goes on to an account of an experiment in which the apparatus was used. In one set of experiments lists of nonsense syllables were learned and then relearned after an interval of five minutes; in the other set, the syllables were relearned after an interval of one week. By using the ratio of actual number of repetitions to total possible number of repetitions as an index of degree of learning, it was found that "underlearning" is correlated directly with degree of forgetting after five minutes, whereas it is not correlated at all with forgetting after a week. This phenomenon may be explained as due to the fact that "overlearning" increases perseveration more than it does association. From Psych Bulletin 21:08:00806. (PsycINFO Database Record (c) 2016 APA, all rights reserved)