Abstract
When students learn how a physical system works, does it help if they also learn how similar systems work? Some college students (concise group) studied a multimedia lesson that explained how hydraulic brakes work, consisting of narrated animation or annotated illustrations. Others (expanded group) received the same lesson along with multimedia explanations of caliper brakes and air brakes presented either after (Experiment 1) or before (Experiment 2) the explanation of hydraulic brakes. Across the combined experiments, students performed worse on retention (d=0.37) and transfer tests (d = 0.30) concerning hydraulic brakes if the lesson also contained lessons on caliper and air brakes; within each experiment, the effects were statistically significant in Experiment 1 (d=0.57 and 0.53, respectively) but not in Experiment 2 (d = 0.23 and 0.17, respectively). Students performed similarly with narrated animations and annotated illustrations.