A systematic re-examination of the list-length effect in recognition memory

The list-length effect (LLE) in recognition memory refers to the phenomenon where performance decreases as the length of the to-be-remembered list increases. The phenomenon has been theoretically important in the literature concerning the sources of forgetting since the existence of the LLE entails that memory interference stems from each individual item (i.e., item-noise) compared to other sources such as interference from pre-experimental experience (i.e., context noise). Regarding the existence of the LLE, Brandt et al. (2019) recently showed that the experimental designs that support a null LLE suffer from confounds regarding the ordering of experimental conditions (i.e., using a counterbalanced within-subjects design). Therefore, with new evidence for a LLE, in the current study, we re-examined the LLE more systematically manipulating different list-length, delay-length, stimuli-type, and study-time (60 conditions), and using a between-subjects design with a large sample size via mTurk (3,600 participants, 60 participants per condition). Results show evidence for a LLE with different amount of interference across different stimulus type and conditions, which supports that item-noise affects recognition memory. Additionally, we utilized a computational model (Osth & Dennis, 2015) to compare the relative amount of interference (e.g., item-noise, context-noise) affecting recognition memory across conditions. We find that although item-noise exists, there is a greater contribution of context-noise in recognition memory.