Mental files theory of mind: When do children consider agents acquainted with different object identities?

Mental files theory explains why children pass many perspective taking tasks like the false belief test around age 4 (Perner & Leahy, 2016). It also explains why older children struggle to understand that beliefs about an object depend on how one is acquainted with it (intensionality or aspectuality). If Heinz looks at an object that is both a die and an eraser, but cannot tell by looking that it is an eraser, he will not reach for it if he needs an eraser. Four- to 6-year olds find this difficult (Apperly & Robinson, 1998). We tested 129 35- to 86-month olds with a modified version of Apperly and Robinson's task. Each child faced four tasks resulting from two experimental factors, timing and mode of information. Timing: Children saw Heinz learn the die's location either before or after they learn that the die is an eraser. Mode of information: Heinz learns where the die is either perceptually or verbally. When Heinz' learning is verbal, he never perceives the die at all. We found that Apperly and Robinson's problem occurs only in the seen-after condition, where Heinz sees the die after children had learnt that it was also an eraser. It vanishes when Heinz learns where the die is before children learn that it is also an eraser. The problem also vanishes when Heinz learns where the die is purely verbally (e.g., “The die is in the red box”) and never sees it. This evidence lets us refine existing mental files theory, and eliminate several alternatives from the literature.