“…Item response theory (IRT) models are useful tools to model the relationship between the categorical outcome variables and the latent continuous traits. Recent work has extended IRT models to model changes in latent traits, leading to the family of longitudinal IRT (L-IRT) models (e.g., Andersen, 1985; Cai, 2010; Hsieh, von Eye, & Maier, 2010; Huang, 2013; McArdle, Grimm, Hamagami, Bowles, & Meredith, 2009; Paek, Li, & Park, 2016; von Davier, Xu, & Carstensen, 2011; Wang, Kohli, & Henn, 2016; Wilson, Zheng, & McGuire, 2012). Within this family, models differ mainly in the following aspects: (1) the measurement model that implies the factor structure of the primary latent traits measured repeatedly, which could either be unidimensional, multidimensional (Hsieh et al, 2010), or hierarchical (Huang, 2013); (2) the relationship of the latent traits over time, which could either be captured by a completely unstructured covariance matrix (Andrade & Tavares, 2005; Cai, 2010; Paek et al, 2016) or by linear/nonlinear change patterns via the latent growth curve (LGC) models (Bollen & Curran, 2006; Duncan, Duncan, & Strycker, 2006); and (3) whether nuisance factors are in place to account for the dependency of the same items administered over time (e.g., two-tier model; Cai, 2010; Paek et al, 2016; Wang et al, 2016).…”