TreeBUGS is an R package that facilitates the analysis of hierarchical multinomial processing tree (MPT) models that are often used in cognitive psychology (Erdfelder et al., 2009). Hierarchical models assume that each participant has a separate set of MPT parameters (e.g., different levels of memory or response bias). Across participants, these parameters follow a continuous hierarchical distribution. In the R package TreeBUGS, the Beta-MPT (Smith & Batchelder, 2010) and the latent-trait MPT model (Klauer, 2010) are implemented. The first approach assumes that MPT parameters follow independent beta distributions, whereas the latent-trait appraoch assumes that the probit-transformed MPT parameters follow a multivariate normal distribution.
Further information about implementation and analysis are found in: