As mentioned in my last chapter, viewpoint intruders are the source of most of my book club critiques when I'm assessing diction of the prose. Below are a few examples.
He noticed the wedding ring on his finger.
She saw the man approaching her.
He felt immense sorrow tugging at his gut.
Viewpoint intruders are blatant and obvious statements about internally executed verbs. The reason that they're a problem in fictional writing is that they're counter to your goal of giving the reader an experience. We want to be a part of the story and share in the experiences of the main character(s).
Viewpoint intruders, found mainly in third-person writing, remind us that someone outside the book is narrating the story. They also make certain sentences much weaker than they would have been otherwise. Unfortunately, you never grow out of using them (at least most writers don't). It's something you have to fix when you revise your work for diction. Nevertheless, knowing is half the battle, so here are some common viewpoint intruders and how to fix them.
He wondered if his mother was still alive. (Omit the intruder and rephrase the sentence as a question. Add an action if needed.)
He thought that she looked especially beautiful tonight. (Change to an italicized thought, and/or omit the intruder. Add an action if needed.)
He noticed/noted that a large bug had crawled onto his hand. (Just cut the intruder.)
He knew that she was an unpredictable woman who was prone to hurling dinner plates at bad guests. (Omit the intruder.)
He saw the bright ribbons of the dancers and was reminded of his home. (Omit the intruder and change the phrasing.)
He felt anxious. (Omit the intruder and describe the emotion in a way that shows us.)
He heard the desperate wail of a baby. (Change the phrasing so he's the object of the sentence. Ex: The desperate wail of a baby reached his ears.)
He dreamed of kissing Alura again. (Change phrasing so his mind is the object of the sentence. Ex: Fantasies of kissing Alura again invaded his mind.)
He remembered when he and his friend swam in the icy ocean. (Omit intruder and add an emotional reaction to the memory.)
He realized she wasn't talking about him. (Omit the intruder. It's not necessary 99% of the time.)