1991 年 33 巻 2 号 p. 97-101
Memory task of a random series of digits was employed to investigate the effects of the repetitive presentation of specific items on the memory performance. Although the recall performance of the repeated items has been considered to improve gradually, Imai and Hosoda (1988) found out a transient decrease in the score of the third presentation of identical stimuli, and named this phenomenon “paradoxical fall”. In the present experiment, the subjective expectation of the repetition was manipulated by the instruction as well as the length of the intervening, nonrepeated trials. The results showed that the effect of repetition factor on the recall score was only significant in the unexpected group under the short-interval condition. This finding supported our hypothesis that the paradoxical fall phenomenon was caused as a result of the mode change in the search process: change from a process without awareness to one in which there is a certain awareness of recognition.