As for the concept of revenge, I think the actions of throwing and getting are not just for revenge to mother.
In the other words, the actions might imply infants' further development of the body and mind. From the
development of the body, the infant could practice to stretch out body(this is one step of the physical development
of human beings); on the other hand, the infant could learn to communicate with others
( whether mother or no). Therefore, the actions of throwing and getting do not
just imply the intenional revenge to the mother, but the pre- state of socialization or institualization in human life.