Effects of similarity and repetition on memory: Registration without learning?

Investigated judgments of the frequency of test items (Y) that were highly similar to studied items (X) to test a prediction made by several memory models: that the judged frequency of Y should be proportional to the judged frequency of X. Whether stimuli were pictures or words, judged frequency of Y was bimodally distributed with 1 mode at zero, suggesting that frequency judgments involve a 2-stage process in which a zero judgment is made if there is a mismatch between retrieved information and the test item. Nonzero judgments, taken by themselves, were consistent with the prediction of proportionality. In 2 experiments, the percentage of zero judgments made to Y increased with repetition of X, but in 2 others the percentage did not change beyond frequency?=?1. The percentage of "new" judgments in recognition memory followed this same pattern. Because the judged frequency of X increased even as X–Y discrimination showed no improvement, the result is characterized as "registration without learning." (PsycINFO Database Record (c) 2010 APA, all rights reserved)