Representational momentum in displacement tasks: Relative object weight matters in toddlers’ search behaviour

Various developmental studies have demonstrated that implied object weight is a key variable in children’s interpretations of motion, such as predicting the objects’ speeds. An additional bias in predictions of object motion is representational momentum (RM), where objects are anticipated to be found in a location farther along in the direction of motion from where they actually are. The present study aimed to evaluate when children begin to be sensitive to relative weight in a RM-related search task. Toddlers (N = 60) aged 2, 2½ and 3 years first visually and manually experienced a heavy ball, a light ball, or both balls at the same time. They then watched one of the balls roll down a ramp and behind a screen with four doors, with a visible barrier placed along the ramp in various positions that would stop the ball’s motion, after which the toddlers were allowed to search for the ball by opening one of the doors. Search accuracy generally increased with age but the accuracy also depended on condition. Relative heaviness in particular led to reduced search accuracy. Further analyses revealed relative heaviness to lead to more searches farther beyond the barrier, adding to the expected RM effect.