You don’t need to teach a child to push harder when confronted with a heavy object. She figures it out. You don’t need to teach a child to pay attention when you shake a rattle. He naturally gets attracted to its sound and motion. You don’t need to tell a child to become calm and joyful when seeing beautiful objects. She just smiles.
The human brain has evolved over centuries to interact with physical objects and react to cues in the real world. Interfacing with mobile apps is increasingly more like interacting with these physical objects. We touch, swipe, tap and tilt them.