To mentally extrapolate the trajectory of a moving object which disappears from sight, it is possible to exploit two different sources of information. One source is the memory of the last visible movement of the object, and the other is its inferred movement through time. It is often assumed that these cues are integrated into dynamical analog mental representations. To investigate the nature of the mental representation of imagined movements, we used a new experimental paradigm for which a causality attribution task was combined with motion prediction task. Participants were instructed to imagine the trajectory of a moving object disappearing behind a screen while estimating the degree to which the movement was caused by another moving object. We show that the predicted movement departs from a correct extrapolation based on accurate memory for velocity. Furthermore the mental representation of the physical and causal structure of the dynamical events did not appear to be as detailed as a theory of mental simulation would predict.