The effects of (i) learner demonstration (using a manipulable model) and (ii) writing for understanding on learning from an animation of a Scotch Yoke mechanism were compared in a time-controlled investigation. Post-tests assessed the quality of the Scotch Yoke mental model acquired in the two learning conditions. On the basis of the Animation Processing Model (Lowe & Boucheix, 2008), we hypothesized that participants in the demonstration condition should outperform those in the writing condition because having to demonstrate the behaviors of the Scotch Yoke would result in deeper processing of crucial dynamic information in the animation. Results of the investigation will be presented at the conference