[1] Together with closely related terms such as 'reflexivity' and 'intersubjectivity', it is now well-established among scholars investigating the evolutionary emergence of human sociality, cognition and communication.
In the case of gorillas and chimpanzees, adult apes have evolved eyes which give away very little information concerning direction of gaze.
Their eyes are dark-on-dark: the iris is dark brown or even black and the same applies to the sclera and surrounding skin.
This feature, combined with the relatively large size of the human eye and its horizontally elongated shape, assists neighbouring conspecifics to detect direction of gaze and, on that basis, engage in mind-reading.
[6] According to evolutionary psychologist Michael Tomasello, a human child normally achieves egocentric perspective reversal—viewing its own mental states as if from the standpoint of others—at around one year of age.