The main characters in "The Giver" novel by Lois Lowry use different politeness principles in their communication. The researchers analyzed the novel to see how the characters use politeness, focusing on the types of politeness principles they applied. They found that the main characters, Jonas and The Giver, used six types of politeness principles, with the most common one being agreement maxims. This shows that the characters in the novel are careful about their language choices and how they interact with each other.