JOURNAL OF VERBALLEARNINGAND VERBAL BEHAVIOR 12, 229-238 (1973) Modality Tags and Memory for Repetitions: Locus of the Spacing Effect 1 DOUGLAS L. HINTZMAN, RICHARD A. BLOCK, AND JEFFERY J. SUMMERS University of Oregon, Eugene, Oregon 97403 Two experiments used a combined frequency- and modality-judgment task to investigate incidental memory for input modalities of repeated words. In both experiments, a series of words was presented in which frequency of occurrence (0, 1, or 2) was orthogonally com- bined with modality of each presentation in such a way that modalities of repeated words either were switched or remained the same. In Experiment lI, the spacing of repetitions was varied. The conclusions were: (a) Frequency judgments increase and then decrease slightly as a function of spacing. (b) Neither the absolute level of judged frequency nor the magnitude of the spacing effect depends much, if at all, on whether the two presentations occur in the same modality. (e) Both modalities of a repeated word are remembered fairly accurately, except at short spacings. (d) The temporal order of modalities is remembered for the most part independently of spacing. (e) Modalityjudgments are most consistent with the hypothe- sis that the spacing effect is due to a failure to encode (or later retrieve) the second occurrence of a word when it closely follows the first. Two recent studies have shown that when a word list is presented in which some words occur in the visual (V) and others in the audi- tory (A) modality, subjects can judge the input modality of an individual word with consider- able accuracy, even after a delay of several minutes (Bray & Batchelder, 1972; Hintzman, Block, & Inskeep, 1972). The two experiments reported here investigated incidental memory for both input modalities of a word that occur- red twice. Although the experiments were concerned with somewhat different theoretical questions, both used the same general technique: A long series of words was presen- ted with the subjects instructed simply to remember the words. Some words occurred only once, in either the V or the A modality, ~The research reported herein was performed pursuant to a grant with the Office of Education, U.S. Department of Health, Education, and Welfare. Con- tractors undertaking such projects under Government sponsorship are encouraged to express freely their professional judgment in the conduct of the project. Points of view or opinions stated do not, therefore, necessarily represent official Office of Education position or policy. Copyright © 1973 by Academic Press, Inc. All rights of reproduction in any form reserved. while others occurred twice, with the modality of the second presentation either the same as or different from that of the first. After presentation, subjects were given a test in which they were to assign each word to one of seven categories--N (not presented), A, V, AA, AV, VA, or VV--according to its history of presentation in the list. From these judg- ments one can assess memory for modality, for frequency, and, in the case of AV and VA, for the order of modalities. Experiment I used this technique to deter- mine whether subjects can remember both modalities of a repeated wordl The experiment was originally viewed as a further test of the hypothesis that repetition of a stimulus enhances its retention by producing multiple memory traces, one for each time the stimulus occurred (Hintzman & Block, 1971). Experi- ment II extended the basic technique to in- vestigate the spacing effect, the fact that repetitions of an item massed closely in time lead to poorer retention than do repetitions spaced farther apart (for a review, see Melton, 1970). The idea was that if traces of different 229