There are several ways by which the reader can obtain information about the characters.
One is by what they say; another is how characters interact with other characters.
A third way is to watch how a character acts because what is said and what is done are not always the same thing. For example, in "The Tell-tale Heart" by Edgar Allan Poe, the narrator insists that he is not insane, but his behavior tells the reader otherwise.
Another way to learn about a character is to study the setting of the story and how the character relates to or acts because of the setting. Setting includes not only the location, but the era in which the story is set. As Jennifer Jordan-Henley of Roane State Community College writes:
Setting - The place or location of the action, the setting provides the historical and cultural context for characters. It often can symbolize the emotional state of characters.
As an example, in To Kill a Mockingbird, to truly understand the hatred of Bob Ewell and his ability to get away with lying about his daughter's rape at the hands of Tom Robinson (a black man), it is important to note that the story is set in the South where, at the time, Civil Rights violations were an everyday occurrence. It is also important to remember that the Civil War may have been over for many years, but the memories and scars are still much fresher in Alabama than they are in the North.
The setting is not just something that the author chooses randomly. He or she uses the setting to prepare the reader's state of mind from the very beginning (also seen with stories by Poe). The setting will help to move the plot along. And with a truly talented writer, the setting will also give deep insights into the true nature of the characters: they will respond the way they do not just because of their interactions with others, but because of who they are based upon their connection to the setting.