Comparing Forgetting Rates Between Item and Relational Memories

Forgetting is an everyday occurrence where an idea that could be recalled successfully is no longer able to be retrieved (Tulving, 1974). Multiple theories suggest how forgetting occurs, such as the decay theory, which suggests that memories are gradually forgotten over time, and the interference theory, in which forgetting occurs because of competing information. Additionally, there are two newer theories which both predict that item representations should be forgotten because of interference and mnemonic discrimination should be forgotten due to decay: the memory system-dependent forgetting hypothesis (Hardt, Nader, & Nadel, 2013), and the representation theory of forgetting (Sadeh et al., 2014). The present study examined these theories by comparing the rate of forgetting for mnemonic discrimination and item recognition over five days. Using the Mnemonic Similarity Task (MST) (Stark & Kirwan, 2019), participants completed memory tasks over a five-day period, allowing for an assessment of both decay and interference effects. Results show that mnemonic discrimination is more prone to decay, while item recognition is more prone to interference-based forgetting. These results supported the present hypothesis, supporting both the memory-system dependent forgetting hypothesis and the representation theory of forgetting. Furthermore, these findings supported Wickelgren’s (1975) model, a quantitative model of forgetting that has been overlooked for decades and predicts that interference and decay contribute to forgetting independently. Overall, this study contributes to the growing understanding of the distinct mechanisms underlying memory decay and interference in the forgetting process.