Chapter 16 is a very interesting part of this novel because in it we see that Jonas, through the memories he is experiencing, is realising the short comings of the society of which he is a part. Note that in this chapter he tells his first ever lie to his parents, when they try to explain to him why love is a "meaningless" word. Then, he whispers to Gabriel one night about his desire to see change in their world and to think about how it could be improved by returning some of the things that have been taken away:
"I don't know how, but there must be some way for things to be different. There could be colours."
Thus Jonas's decision to not take the pills represents his first act of rebellion against the society he is part of, and which he realises has robbed him and his fellow people of so many rich aspects of life.