Chimpanzees understand psychological states - the question is which ones and to what extent.

New data suggest that relatively drastic revisions are needed in our theoretical accounts of what other animal species understand about the psychological states of others. Specifically, chimpanzees seem to understand some things about what others do and do not see, or have and have not seen in the immediate past, as well as some things about others' goal-directed activities. This is especially so in competitive situations. They clearly do not have a human-like theory of mind, however, and so the challenge is to specify precisely how ape and human social cognition are similar and different.