[Paradoxical fall in repetitive learning of a random series of digits].

In this study, on each trial subjects were presented visually a different random series of nine digits, and required to memorize and recall them immediately. Among a sequence of trials there were three repetitive learning trials, a few trials apart one from another. On these trials an identical series of nine digits was presented repeatedly. Recall rates of the series of digits on repetitive learning trials rose from the first trial to the second, and, by contraries, fell on the third. We call this fall "paradoxical fall," since it is contrary to the expectation of standard theories of learning. It was pointed out that we should investigate the detailed cognitive process, i.e., the microcognitive process, in learning.memory of simple series of digits, because it involves the important basic cognitive process of learning.memory.