Mass perception of objects in collision events from a developmental perspective

Abstract

Around 5.5 to 6.5 months of age, humans first start to perceive the relationship between size and mass in simple collision events by attending to the size of the agent object (Kotovsky & Baillargeon, 1998). Infants of this age perceive a greater displacement after collision with a large object and a lesser displacement with a small object. The results are based on infants’ looking time responses to a large and small object propelling a patient object to one distance, the endpoint of the screen. It is unknown how infants and adults would perceive the same events if a large and small object propelled a patient object to size appropriate (congruent) and size inappropriate (incongruent) distances. Furthermore, uncertainty remains about how infants and adults perceive object brightness and sound pitch, and their mass cues in collision events. It is documented that adults judge dark coloured objects and lower pitch sounds to be heavier in weight than bright coloured objects and higher pitch sounds (Walker, Francis, & Walker, 2010; Walker, Walker, & Francis, 2012). Similarly, infants around 10 months of age associate low pitch sounds with dark coloured objects, and high pitch sounds with bright coloured objects (Haryu, & Kajikawa, 2012). Moreover, it is unknown at what point in development humans start to perceive and process the differences between size of an agent object and a patient object. Specifically, the perception of the collision between an agent object that is constant in size and a patient object that varies in size. To these means, this thesis presents a series of experiments that examine adults’ reasoning and infants’ perception of object size of both agent and patient object, object brightness and sound pitch objects emit during collision and their mass cues in the collision events. Chapter 3 examines adults’ reasoning about object size, object brightness and sound pitch objects emit during collision and their cues to mass in three-dimensional computer-generated collision events. Results suggest that adults sometimes base their mass judgements on visual cues 6 such as object size and object brightness. However, adults fail to consider sound pitch during collision as a cue for mass in the collision events. Chapter 4 investigates the 6-to-7-month old infants’ perception of object size and object brightness separately and together and their cues to mass in 3D computer-generated collision events. Results in Chapter 4 indicate that these experiments fail to provide evidence that infants perceive mass cues of object properties size, brightness, and size and brightness in collision events. Chapter 5 concerns the 10-to-11-month old infants’ perception of object size of agent object and patient object and their cues to mass in 3D computer-generated collision events. Results in Chapter 5 indicate that these experiments fail to provide evidence that infants use mass cues of object size of agent and patient object in collision events. Results of this thesis clarify how adults reason and how infants perceive object size, object brightness and sound pitch and their cues to mass in collision events. Furthermore, this thesis clarify how infants use object size of the agent object and the patient object and their cues to mass in collision events.