Adults’ understanding and 6-to-7-month-old infants’ perception of size and mass relationships in collision events

Humans first start to perceive the relationship between object size and mass in simple collision events at about 5.5–6.5 months of age. They perceive this link in simple collision events by attending to the size of the moving object and anticipating a greater displacement after collision with a large object and a lesser displacement with a small object. The results this aforementioned experiment is based on infants’ responses to a large and small object propelling a stationary object to the same distance (long distance). It is unknown how infants would perceive the same events if a large and small object propelled a stationary object to size appropriate (congruent) and size inappropriate (incongruent) distances. This paper aims to investigate this with adults (experiment 1) and 6-to-7-month-old infants (experiment 2). The first experiment served to validate our computer-generated collision events, by asking adults (N = 24) to rate the likeness of collision events happening in real-life, based on object size. In the second experiment, we tested this phenomenon in infants (N = 16) using the looking time paradigm. Results from the first experiment revealed that our computer-generated collision events are in line with adults’ assumptions of size-appropriate and size-inappropriate distances that the cube is propelled to by the small and large ball. Adults rated congruent test events as more likely than incongruent test events when asked how real-life-based they were. Results from the second experiment revealed infants distinguished between the sizes by preferring to look at the large ball longer than the small ball. However, the infants did not differ in their looking times for congruent and incongruent test events for small or/and large balls. For that reason, we conclude infants can distinguish between the sizes of the balls but are unable to perceive the size and mass associations in collision events.