Journal of Experimental Psychology: Human Learning and Memory 1975, Vol. 104, No. 1, 31-40 Spacing Judgments as an Index of Study-Phase Retrieval Douglas L. Hintzman, Jeffery J. Summers, and Richard A. Block University of Oregon It is hypothesized that the ability of subjects to judge how far apart two presentations of a word were in a list reflects study-phase retrieval of the trace of the first presentation of the word by its second presentation. Ex- periment 1 supported this hypothesis by demonstrating that the accuracy of spacing judgments for associatively related pairs of words, like that for repeated words, was high compared to that for unrelated words. Experi- ment 2 used spacing judgments to measure retrieval upon repetition of a homograph. In three conditions, context words accompanying a homograph on its two presentations were either the same, biased the same meaning, or biased different meanings. In all three conditions, later spacing judg- ments were more accurate than in an unrelated-word control. Accuracy did not depend on whether the two context words biased the same meaning or different meanings of the homograph. If a subject studies a word list in which some of the words occur twice, and later is shown one of the repeated words and asked to judge the spacing of presentations of the word in the original list, he is able to do so with some accuracy. Performance in a control condition, requiring a judg- ment of the spacing of two unrelated words that occurred one time each, is much poorer. This result was interpreted by Hintzman and Block (1973) in terms of study-phase retrieval. They assumed that the second presentation of a word (P%) retrieves the trace of the first (Pi), and that this re- trieval results in an implicit judgment of the recency of PI. The implicit recency judgment itself is then stored in memory, and when it is retrieved on the later test, the subject can use it in making the required judgment of Pj-Pg spacing. If this interpretation is correct, then spac- ing judgments might be used in certain situations as an unobtrusive index of spon- taneous study-phase retrieval. The distri- bution of spacing judgments in a given con- dition should consist of two components: This study was supported by a research grant from the Office of Education, U.S. Department of Health, Education, and Welfare, and by Grant GB-40360 from the National Science Foundation. Requests for reprints should be sent to Douglas L. Hintzman, Department of Psychology, Univer- sity of Oregon, Eugene, Oregon 97403. judgments that are guesses, and those that are based on recency information encoded when retrieval took place. Thus, the de- gree to which the second of two events retrieves the trace of the first should be reflected in the accuracy of the mean judg- ments of their spacing, given on a later test. This paper reports two experiments that replicate the Hintzman and Block (1973) finding, confirm a prediction of this inter- pretation of spacing judgments, and demon- strate how spacing judgments can be em- ployed as a tool to investigate spontaneous study-phase retrieval. Experiment 1 compared judgments of spacing of three types of word pairs: related words (e.g., QUEEN-KING) ; unrelated words (e.g., SPIDER-TABLE) ; and repeated, or same words (e.g., WAR-WAR). It was assumed that the second member of an associatively related pair would tend to retrieve the trace of the first member, thus, according to the hypothesis, providing the necessary informa- tion for performance on the later spacing- judgment test. Two comparisons are im- portant: (a) If spacing judgments given to pairs of related words are more accurate than those given to pairs of unrelated words, the study-phase retrieval hypothesis is sup- ported, (b) If the hypothesis is accepted, then the degree to which related-word judg- ments approximate those given to same- 31