How can we test whether someone is able to ascribe beliefs to others?
Here is one quite famous way to test this, perhaps some of you are even aware of it
already.
Let's suppose I am the experimenter and you are the subjects.
First I tell you a story ...
‘Maxi puts his chocolate in the BLUE box and leaves the room to play. While he is away (and cannot see), his mother moves the chocolate from the BLUE box to the GREEN box. Later Maxi returns. He wants his chocolate.’
In a standard \textit{false belief task}, `[t]he subject is aware that he/she and
another person [Maxi] witness a certain state of affairs x. Then, in the absence of
the other person the subject witnesses an unexpected change in the state of affairs
from x to y' \citep[p.\ 106]{Wimmer:1983dz}. The task is designed to measure the
subject's sensitivity to the probability that Maxi will falsely believe x to obtain.
I wonder where Maxi will look for his chocolate
‘Where will Maxi look for his chocolate?’
Wimmer & Perner 1983
Recall the experiment that got us started.
These experimenters added an anticipation prompt and measured to which box subjects looked first \citep{Clements:1994cw}.
(Actually they didn't use this story; theirs was about a mouse called Sam and some cheese, but the differences needn't concern us.)