The development of children's concepts of invisibility.

One of the most striking examples of appearance-reality discrepancy is invisibility - when something has no appearance yet still exists. The issue of invisibility sits at the juncture of two foundational ontological distinctions, that between appearance and reality and that between reality and non-reality. We probed the invisibility concepts of 47 3-7-year-olds using two sets of tasks: (1) an entity task, in which children were queried about the visibility and reality status of a variety of both visible and invisible entities, and (2) two standard appearance-reality tasks. Results showed that children's concepts of visibility and reality status are intertwined, and that an understanding that some entities are impossible to see develops between the ages of 3 and 7.