Greater Interference From Multiple Exposures During Memory Retrieval Drives More Memorable and Forgettable Experiences

Our everyday experiences share many overlapping features, as we often engage in repeated activities and routines. This leads to interference across our experiences, making it difficult to remember specific, unique events. Hippocampal pattern separation enables the discrimination of highly similar experiences to be stored orthogonally, especially in the face of interference. Mnemonic discrimination tasks have been designed to tax hippocampal pattern separation by including perceptually similar "lure" stimuli during memory retrieval. However, we experience vast interference beyond a single instance of overlap. Thus, a key feature of our memory system is to overcome this high interference. Furthermore, some experiences tend to be better remembered by most people than others, a feature known as memorability. However, it is unclear how memorability may impact the effect of interference on memory. To this end, we designed a mnemonic discrimination task with multiple forms of interference, such that target (repeated) and lure (similar) images of a baseline image were shown to participants during a memory test designed to increase interference during memory retrieval. We additionally varied image memorability by including memorable and forgettable images to examine interactions with interference conditions. We found that greater interference during retrieval enhanced lure discrimination for memorable images, but impaired lure discrimination for forgettable images. This suggests that interference does not uniformly impact memory, with greater interference in memory leading to exaggerated memorable and forgettable experiences.