A Systematic Reexamination of the List-Length Effect in Recognition Memory

Abstract

The list-length effect has been crucial in understanding the sources of forgetting in recognition memory, especially whether forgetting stems from interference generated by other items in the study list. However, there has been inconsistent evidence for the effect, and recent studies have found various confounds in the experimental design. The present study reexamined the list-length effect by controlling confounds that have been reported. We also systematically manipulated various factors such as the list length, study time, delay, and stimulus type and tested a large sample to examine the robustness of the effect (i.e., radical randomization). Results showed evidence for a list-length effect across the conditions, and we find that the square root function best describes the list-length effect. By utilizing a computational model, we also show that although the list-length effect exists, there is, in general, a greater amount of interference stemming from other sources in recognition memory (e.g., previous contexts). Public Significance Statement Asking whether one has encountered a certain item or not in the past (recognition memory) is one of the simplest ways to examine human forgetting. Moreover, it is generally expected that if there are more items to remember, memory performance will be worse (list-length effect). However, the existence of the list-length effect has been a long-standing debate. The present study shows that there is strong evidence for the list-length effect across various conditions. At the same time, the results show that forgetting in recognition memory is not only driven by how many items there are to remember (the length of the list), but also by other factors such as how many times one has encountered the items in the past.