In several publications, Boker and colleagues (Boker, 2002; Boker & Graham, 1998; Boker & Nesselroade, 2002; Boker, Neale, & Rausch, 2004) have drawn attention to oscillating movements and the importance of oscillating movements in psychology. Different ways to describe and estimate such oscillating movements were proposed by them. Most recently, Boker et al. (2004) introduced the multivariate latent differential equation (MLDE) approach, which is a model as well as an estimation procedure. The model formulates a differential equation model on the latent variable level. The estimation procedure uses structural equation modeling (SEM), in particular the program Mx (Neale, Boker, Xie, & Maes, 1999), to simultaneously estimate the parameters of the differential equation model and the measurement model. In the estimation procedure, the differential equation model is approximated.