People make mistakes, so characters should make mistakes. If a character hasn’t made a mistake or suffered a misinterpretation, then I feel as though the writer is missing an opportunity. Mistakes help credibility, and misinterpretation begins with perception. When two people interact, they might make assumptions about each other’s body language as well as their words. People communicate a great deal with their body language, and it’s a great tool for a writer to show and not tell, and for a character to get the wrong idea about someone else because they’re not being looked in the eye. Without knowing why the other character is doing this, the reader will be inclined to follow your lead with assumptions, unless you want them to know that a mistake is being made, in which case they’ll get caught up in the misunderstanding, having information your main character doesn’t.
When there is a single viewpoint to behold, the other character’s motivation is spoken through the clues of their actions as well as dialogue. Imagine a duplicitous character: A mistake such a slip-up in conversation, or a contrary action to words (shaking head while saying yes). Imagine a friendship: A mistake in putting trust in the wrong person, leading to betrayal. Imagine an athlete or hero: A misinterpretation of what is necessary to achieve a goal or overcome a hurdle, leading to injury of physical self or pride. Imagine a character failing at a task they’ve poured their whole self into: A mistake made laying blame in those around them. It can be a pivotal moment in your story, if the mistake or misinterpretation is dramatic enough, or the realisation of a mistake can finish shaping your character to what you planned on them being.
Mistakes and misinterpretations are not only a way to lend credibility to your characters, they can also gain sympathy from readers and raise emotional investment. Everybody’s been there, we’ve all made mistakes. It’s something most people naturally feel empathy for. It’s also a fantastic plot device, to strip your character of all they know and having to start again, or forcing them to change a path because they’ve gone in the wrong direction. Mistakes can be comedic or tragic. However you look at it, your character will feel more like a real person, and that’s why making mistakes is good.