In the last of a series of experiments 48 3-5-year old children were tested on an alternative naming game with "synonyms," e.g., if puppet calls the depicted item a "rabbit" the child has to call it a "bunny," or the child has to judge puppet's performance when roles are reversed. The game was also played with categories (rabbit-animal), name/colour (rabbit-black), colour/colour (black-white), and part/part (head-tail). The younger children (=3.5 years) had severe problems with "synonyms" and categories (alternative names for the items, 80% correct). Children's increasing success with age on the alternative names tasks was closely paralleled (.53 = r = .72) by their mastery of the false belief task in which they had to predict that a mistaken story character would look for a desired object in the wrong location. For explaining the synchrony between alternative naming and understanding false belief we draw on the Piagetian idea that children come to represent perspective at some point in their development. To apply this idea to the alternative naming game we draw on the philosophical discussion about sortals (terms that specify what sort of object something is) creating perspective differences.