Title: Recursive partitioning for multinomial processing tree models: A new implementation based on the partykit package Authors: Florian Wickelmaier and Achim Zeileis Affiliation: University of Tuebingen Abstract: Multinomial processing tree (MPT) models are a class of statistical models for categorical data. The parameters of such models represent the probabilities of cognitive processing steps executed to arrive at observable response categories (Riefer & Batchelder, 1988). We present an implementation of model-based recursive partitioning (Zeileis, Hothorn, & Hornik, 2008) for multinomial processing tree models that is based on the new partykit infrastructure (Hothorn & Zeileis, 2014). Recursive partitioning can be used to investigate the effects of subject covariates and, in doing so, uncover individual differences in cognitive processes. The procedure is illustrated with examples from memory research. Hothorn, T., & Zeileis, A. (2014). partykit: A modular toolkit for recursive partytioning in R. Working paper 2014-10. Working Papers in Economics and Statistics, Research Platform Empirical and Experimental Economics, Universitaet Innsbruck. http://EconPapers.RePEc.org/RePEc:inn:wpaper:2014-10 Riefer, D., & Batchelder, W. (1988). Multinomial modeling and the measurement of cognitive processes. Psychological Review, 95, 318-339. Zeileis, A., Hothorn, T., & Hornik, K. (2008). Model-based recursive partitioning. Journal of Computational and Graphical Statistics, 17, 492-514.