Of course we aren't independently thinking in that sense: we use other humans as points of reference to make a pattern for what thinking is, beyond simply reacting to stimuli.

If real AI is to ever exist, it would probably be necessary to develop a way for several AIs to socialise so they can start develop a ways to conceive of and perceive themselves as if they were an outsider observing, the sameway we do it before and during puberty.

We all exist and create normal by referencing our surroundings - control what we are exposed to and you affect how we develop. The same is true for AI.