Human mind - magic mind

To really understand the exeptional quality of the creatures we are it seems indispensable to peer at the complex mechanism of the work of our human minds. It may seem unexpected but in the meantime we will expose what actually the Shakespeare's genius consists on (among others, obviously).

Let's try to resolve a simple riddle we could give to any child. We need to viualise such situation:
Sally and Ann are two dolls. Sally has a ball. She puts the ball under the cushion on the armchair. Then she leaves the room. While she's not there, Ann grabs the ball and she hides it in the box. That's when Sally comes back. According to Sally's knowledge, where is the ball?

Most of the children at the age of 4 or less might answer that Sally thinks that the ball is in the box. Why is that? Simply because kids are not capable to set their knowledge apart from the others' one until they reach the age of 4. It means that they literally can't understand that Sally might think in any other way than they do.
These who have already reached the age of 4,5 and more, might answer correctly - they have acquired something we call Theory of Mind. These children already know that other people have their own minds and that they can think in a totally different way. But this is only a second stage of the Theory of Mind. To know that someone is thinking about something.
Us, humans, can reach the fifth or, according to some researches, even sixth stage. You can verify at which stage you are by reading such story:
Peter believes [1] that Jane thinks [2] that Sally wants [3] Peter to suppose [4] that Jane has a plan [5] to convince Sally [6] that the ball is under the cushion. These are six different assumptions which can make you feel dizzy - as you can sometimes feel when reading Shakespear: his stories exeptionally frequently include such complex and based on all of the 6 stages phrases.
Do you have any guess what the acquirement of the Theory of Mind could be useful for?
How about...lying?

Next time, we will see how our relatives make use of this ability. That's right - it seems that we are not the only ones. But we are probably the only ones to reach more than two stages.