Every species communicates. So far, other than talking birds, humans are the only ones who can speak and write languages.
1. Word Choice: If Dick chooses the wrong words to communicate what he needs or thinks, he may spark a battle with sensitive Sally. Blunt Jane may intervene and try to explain what each person meant and make the situation worse. The topic can be anything. “You always” and “You never” are fighting words. Start off a sentence with either and the game is on.
2. Physical Limitations: Dick may not be able to talk because he has laryngitis or has been cursed by a witch and can only croak. He may speak, but Jane can’t hear because of their surroundings, distance, or she is hearing impaired. Let’s say Sally needs to communicate something to solve the story problem or scene goal. Jane can’t hear/understand her because they are too far apart, the phone has static, or they are muffled by burkas. Sally will have to work harder to achieve her goal. Dick can be forced to keep silent because he is afraid to speak or because he is legally or physically gagged.
3. Experience: Dick and Jane may not be able to communicate their needs or wants sufficiently because they have completely different backgrounds. Dick may try to tell her how something was or why he wants to do something. Jane won’t get it because she never had that experience and can’t relate to or imagine it.
4. Perception: Perception is 9/10 of reality. Dick may perceive a situation in a certain light. Jane might perceive it to be the opposite. If Dick is wrong in his assumptions, he will go after the wrong suspect or accuse Jane of something she didn’t do. If Jane perceives Sally to be a superficial slag, she is unlikely to help Sally or will discount the threat that Sally the vampire truly is. Dick and Jane can be talking about different things, but think they are talking about the same thing. They can be talking about the same thing but think they are talking about different things. Cross purpose dialogue can be fun or tense.
5. Emotions: If Dick is furious and Jane is depressed, neither one of them will be able to “hear” what the other person is saying. Discordant emotional states can effectively shut down a necessary conversation. Dick can tell Jane, “I can’t listen to you right now, I’m too pissed off.” Jane can tell Dick she doesn’t really care who did what at work because she’s exhausted, and irritated, and just doesn't give a hoot at the moment. A character who is uncomfortable with an interrogation will try to change the subject. They might keep talking about fly fishing instead of answering questions about a murder.
6. Culture: We all use cultural shorthand in our conversations. If Dick tries to explain something to Jane, she might not understand the references. Her way of looking at the world may be in total opposition to Dick’s viewpoint. Trying to clarify these differences can be fun, tragic, or tense.
7. Religion: If Dick is Christian and Jane is Muslim, it is possible they will negate anything the other says based on prejudice about each other’s belief systems. If Sally believes in God and tries to convince atheist Dick to do something because God would want him to, she will fail. Dick will not accept that a being he doesn’t believe in is asking him to do something. The carrot of eternal life or the stick of hell won’t be selling points to her thematic argument.
8. Language: If Dick is forced to deal with people who don’t speak his language, he’ll have to resort to the basics: hand gestures, facial expressions and sharing one word at a time. Misunderstandings are inevitable. Differing languages can be a conflict at any story level. Debates about accommodating different languages can be a theme or the premise for a Literary or Science Fiction / dystopian tale. It can be a scene goal problem if Dick is trying to explain his situation to a foreigner or trying to gain information from someone who can’t understand him.