When a good fit is not good enough: A case study on the Final Ritard Henkjan Honing Abstract: The relation between music and motion has been a topic of much theoretical and empirical research. An important contribution is made by a family of computational theories, so-called kinematic models, that make an explicit relation between the laws of physical motion in the real world and expressive timing in music performance (see Friberg & Sundberg, 1999). These models were shown to have a good fit with a variety of empirical data, most notably that of the final ritard in music performance: the typical slowing down at the end of a music performance. However, the predictions of these kinematic models are independent of (1) the number of events, (2) the rhythmic structure, and (3) the overall tempo of the performance; These factors have no effect on the predicted shape of the ritardando. Computer simulations of a number of rhythm perception models show, however, a large effect of these structural and temporal factors. They are therefore proposed as a perception-based alternative to the kinematic approach. While a final ritard might coarsely resemble a square root function (according to a kinematic model), the predictions made by perception-based models are also influenced by the temporal structure of the musical material that constraints possible shapes of the ritard, and it can therefore be considered a potentially stronger theory than one that simply has a good fit (Roberts & Pashler, 2000).