Young children's judgments of relative mass of two objects in a head-on-collision event

The purpose in this study was to investigate the ability of young children to judge the relative mass of two objects depicted on a CRT monitor as colliding head-on with each other, and to determine which feature of a collision event they depend on for their judgments. In the first experiment it was shown that half of the 4-year-olds and most of the 5-year-olds and 6-year-olds consistently judged the slower object to be heavier when the velocities of the two objects before collision were the same and those after collision were different. In the second experiment young children's judgements of relative mass in noncollision events in which two objects only moved in opposite directions at different speeds were examined. Results showed that half of the 5-year-olds and most of the 6-year-olds tended to assume consistently that the slower object was heavier. However, the 4-year-olds did not show any clear tendency. The third experiment was planned to examine young children's judgments of relative mass in different collision events in which only the precollision velocities of two colliding objects were different: half of the 6-year-old children judged the slower object to be heavier, but the rest of them and half of the 5-year-old children consistently gave the opposite responses. These were based upon the delay between the starts of motion of the two objects. The 4-year-olds did not show any tendency, as in experiment 2. The results indicate that young children can specify the kinetic information about relative mass from the kinematics of collision events when viewing an appropriate collision event, and that both the precollision phase and the postcollision phase contribute to the judgement of relative mass.