the capacity to imagine or form opinions about the cognitive states of other people: What does the other person know? What behavior is that person most probable to take? Theory of mind is an vital element of crediting beliefs, aims, and wishes to other people, particularly in effort to foretell their actions. It starts to show up around 4 years of age in humans; there has been substantial controversy about whether non-human animals retain this capacity.
THEORY OF MIND: "Being six years old, your daughter should possess skills in line with the theory of mind by now."