Jonas changes from an automatically obedient child to a wise, mature young man throughout the book.
In the beginning of the book, Jonas is just a regular Eleven in his community. He does what he is told, and does not question things. Yet he is thoughtful and introspective. When he feels nervous about the Ceremony of Twelve, he carefully tries to give the emotion an exact name.
During his ceremony, the Chief Elder describes Jonas’s traits: intelligence, integrity, courage and wisdom. They do not mention his other attribute, obedience, because everyone in the community is obedient.
When Jonas receives his rules, he understands that he is different from the rest of his classmates. His rules are very short, and include strange ones like the ability to lie and restrictions on dream-telling and medication.
Jonas’s training changes his perspective on his community. He begins to receive memories, and see how things have been different in the past. Jonas is shocked when he learns that he will receive memories from the past, and from other places.
I don't know what you mean when you say 'the whole world' or 'generations before him.' I thought there was only us. I thought there was only now." (ch 11, p. 78)
Jonas learns the reality of the world without Sameness. As he learns how the world has changed, he changes too. He soon grows confused, and finally dissatisfied, with the community’s lack of color and choices.
When Jonas asks to see a release, he realizes that release means the person is killed. He cannot believe that his father killed a newborn baby. He comes to understand that his community harbors dark secrets.
Upon this realization, Jonas decides to leave the community and return the memories back to the people. When he finds out Gabe is going to be released, he leaves earlier and takes the baby with him.
Jonas has gone from an immature, instantly obedient child to a rebel. He runs away, and risks immediate death if caught. Eventually, he makes it to Elsewhere and rescues Gabe too.
Lowry, Lois (1993-04-26). The Giver (Newbery Medal Book). Houghton Mifflin Harcourt. Kindle Edition.
The giver's,actually whole community's,memories change the Jonas.Lowry does it by using the happiness,pain,love,colors etc. especially emotions and feelings.This is important because main idea in the book is this changing.You need to read the book and find this emotions and nee to contrast after and before the treatment of "receiver".