The representation of things and properties is a fundamental issue in conceptual modelling. Important theoretical issues surrounding the representation of things and properties remain unresolved. For example, proponents of object-role modelling argue that there should be no distinction between things and properties, while proponents of entity-relationship modelling argue that the distinction is important but provide ambiguous guidelines about how the distinction should be made. In this paper, we use ontological theory to support our arguments about how things and properties should be represented. We describe an experiment that we undertook to test whether an ontologically sound representation of things and properties enabled users to better understand a domain than two other alternative, widely used representations. Our results provide evidence to support the use of ontologically sound representations of things and properties in conceptual modelling.