Bayesian modeling of the Mnemonic Similarity Task using multinomial processing trees

The Mnemonic Similarity Task (MST, Stark et al. in Neuropsychologia 51:2442–2449. https://doi.org/10.1016/j.neuropsychologia.2012.12.014 ) is a modified recognition memory task designed to place strong demand on pattern separation. The sensitivity and reliability of the MST make it an extremely valuable tool in clinical settings. We develop new cognitive models, based on the multinomial processing tree framework, for two versions of the MST. The models are implemented as generative probabilistic models and applied to behavioral data using Bayesian graphical modeling methods. We demonstrate how the combination of cognitive modeling and Bayesian methods allows for flexible and powerful inferences about performance on the MST. These demonstrations include latent-mixture extensions for identifying individual differences in decision strategies, and hierarchical extensions that measure fine-grained differences in the ability to detect lures. One key finding is that the availability of a “similar” response in the MST reduces individual differences in decision strategies and allows for more direct measurement of recognition memory.