Abstract
An object's centre of mass (COM) is determined by its shape and density distribution. To assess whether the human visual system can detect an object's COM from both shape and material properties, we created computer-generated images of goblets made of different materials (e.g., glass, polystyrene) that were either uniform or made of composite materials (e.g., glass and gold) and positioned upright or upside down near a table ledge. Observers were instructed to indicate whether the goblet was more likely to fall off the table or right itself. The critical angle (CA), the angle at which the goblet is equally likely to fall or right itself, was used as a measure of perceived object stability. Participants rank-ordered materials by density on a questionnaire after completing the experiment. If object stability were judged in accordance with physical laws, then we would expect no change in the CA across uniform material objects, while we would expect differences in the CA depending on the relative position of materials for composite material objects. The results show that observers correctly recognize that change to a uniform object's material will not affect its stability. Importantly, perceived and true material density were positively correlated suggesting that observers have a good representation of relative material density. Results for composite material objects revealed that the perceived CA changes with the true CA, suggesting that observers use this accurate representation of relative material density to assess object stability. We conclude that the human visual system is able to form a reliable estimate of an object's COM from shape geometry and material properties that is used to assess an object's behaviour.
Meeting abstract presented at VSS 2014