Global subjective memorability and the strength-based mirror effect in recognition memory

Between-list manipulations of memory strength through repetition commonly generate a mirror effect, with more hits and fewer false alarms for strengthened items. However, this pattern is rarely seen with within-list manipulations of strength. In three experiments, we investigated the conditions under which a within-list mirror effect of strength (items presented once or thrice) is observed. In Experiments 1 and 2, we indirectly manipulated the overall subjective memorability of the studied lists by varying the proportion of nonwords. A within-list mirror effect was observed only in Experiment 2, in which a higher proportion of nonwords was presented in the study list. In Experiment 3, the presentation duration for each item (0.5 vs. 3 sec) was manipulated between groups with the purpose of affecting subjective memorability. A within-list mirror effect was observed only for the short presentation durations. Thus, across three experiments, we found the within-list mirror effect only under conditions of poor overall subjective memorability. We propose that when the overall subjective memorability is low, people switch their response strategy on an item-by-item basis and that this generates the observed mirror effect.