The way your characters react is the way we get to know them. Write a scene in which your characters are forced to react.
Thought or emotion crosses the line into plot when it becomes action and causes reactions. Until then, attitudes, however interesting in themselves, are just potential, just cloudy possibilities.
This is not necessarily purely physical action. It could be a look, stance, grimace or gesture – any physical manifestation of attitude or personality. Sometimes even the failure to act tells us more about character than an overt action.