The dictionary definitions are:

Internal speech, or verbal stream of consciousness is thinking in words. It also refers to the semi-constant internal or interior monologue we has with ourselves at a conscious or semi-conscious level. In fiction, it is a form of stream-of-consciousness writing that represents the inner thoughts of a character.

Introspection is the examination or observation of one’s own mental and emotional processes. In fiction, introspection can be extremely valuable to getting to know the character as the character gets to know himself

And the answer to the difference between internal monologue and introspection: Stream of Consciousness (Internal Speech or monologue) deals more with sensory input whereas interior monologue focuses on the processing of ideas. Any good soliloquy found in classical literature could be held up as an example of interior monologue. But stream of consciousness doesn’t handle morality or problem solving. It lives inside the moment and does not consider the past or future. Interior monologue considers the moment with reflection and planning.

And with those definitions in mind, here’s the question I received from the writer:

I use internal monologue and introspection interchangingly and  in a variety of ways. For one thing, through internal thinking, it is the only time the reader can know the character’s truths  as he sees it. It’s a time to reflect on the past and it’s a time to respond to the present or to plan for the future. It’s a place where the author can drop a clue to the past or piece of back story or even foreshadowing.

Here are examples:
Truth:
Joe couldn’t tell her how he really felt. She wanted him to say he loved her, but he couldn’t. He’d learned that he couldn’t love anyone when he didn’t love himself.

This example allows the reader to understand more about Joe and why he rejects friendships and love. It also shows his attempt to view others as to what they are thinking. He could be right but he could be wrong. This leaves the reader with a question.

The past:
Looking at Susan today drew him back five years earlier when they’d first met. The memory sent a chill up his spin, recalling her face tilted toward the sky, the sun shining on her hair. Why couldn’t he allow those feelings to surface today?

This Internal monologue asks a direct question and leaves the reader with the desire to know why. This works as a hook to pull readers into the story.

The Future:

Tom’s mind spun with ideas. He had to do something. Time wouldn’t allow him to weigh every option. She needed his help, and it had to be now. Possibilities filled his mind until one stood out among the rest. He knew what he had to do.

Another effective hook.  If a chapter or scene ended with this line, readers would be drawn to turn the page and start the next section to learn the answer.

Foreshadowing:

A shudder rolled over Susan’s shoulders as she headed for the basement. Why did she dislike this place? She knew. It was too much like a grave. A cellar was underground, and Susan preferred the light, not the dank gloom of a cellar.

Foreshadowing is a great way to draw readers into the story. They are alerted, if they’re thinking, that something is going to happen underground. Will Susan get trapped in a cellar or is it more the darkness that frightens her? Readers know that something is going to happen.  Another good hook.

No matter what you call it –  Internal monologue, Introspection, or Stream of consciousness – the examples show you how it can be used with purpose. Sometimes going into the character’s thoughts can explain a reaction or express the character’s emotions not shown because the scene was in the another character’s POV, but these thought can also provide excellent hooks that draw readers into the story and make them turn pages.

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