I've been thinking about head-hopping in narrative prose. First let me say that my first and pretty much only rule of writing is that anything goes, as long as it's a considered technical choice and serves the narrative. So if you want to head-hop in your fiction, go ahead. But imho you'll need serious writing chops if you want to take a reader along with you.
Head-hopping generally happens in third person limited, i.e. a narrative filtered (we use the term focalised) through the perspective of a specific character. So using third person (he, she, it, or they if you're punchy) and keeping the perspective tightly focused on (limited to) what that person knows. It's the most commonly used perspective in contemporary fiction.
Head-hopping is when the narrative shifts from being focalised through one character to another character in quick succession, by which I mean between paragraphs or even sentences. It's the most common technical issue I see in narrative prose. NB I'm not talking about having multiple povs within an extended piece, where individual scenes or chapters have a new pov. I'm talking about rapid shifts, sometimes back-and-forth, within continuous scenes.
Why does this matter? Well, as I say, if you've got the chops, go ahead and polyphonically knock my socks off. But it's not easy. I did write a piece once that did this, to prove to a friend that it could be done - yes, proving someone else wrong is a great reason to write a piece of fiction. It was very tricky, and the pov only shifted a handful of times, after each character had had a few paragraphs to establish their perspective. The story, which was called "The Lost" (thematic link to form) was about two people bringing their understanding of each other closer and closer together (content linked to form). My friend didn't notice until I pointed it out. And then she was furious with me. Yay friendship!
But this isn't what I'm talking about. I'm talking about those sudden shifts, where the reader is left uncertain whose perspective they're following, and is thrown out of the text. It generally happens in scenes where two or more characters are in conversation with each other. I think it occurs for two reasons, both of which ultimately come down to control over point of view.
The author is visualising the scene as if it's a film or piece of TV happening in front of them. This means that they are not themselves anchored in the perspective of one of the characters. They've not decided through whom the scene is focalised.
This means that they're not fully immersed in the experience of the pov character - which means in turn that they're not fully immersed in the reality of the scene.
Basically I'm saying that the scene is not yet fully imagined. What's most likely happening in this stage of writing is that the author is establishing the dramatic parameters of the scene, i.e. what are the beats in the conversation; how is power shifting around; what individual character trajectories are being followed, and so on. Because the scene is in the process of being imagined, the pov shifts around to help with this work.
The solution is to realise that the scene is effectively still in draft. You need to be clear on whom this scene needs to be focalised through; fully immerse in their perspective; and rewrite the scene filtered through that consciousness. (This doesn't usually involve much rewriting. It does mean more thinking, and more craft.)
I nearly wrote "filtered through that lens" there, because it's a good way to get the message across. But I consciously decided against. Because head-hopping often arises when the writer is operating a camera on the scene. And narrative prose is not primarily a visual medium. The recording device you're operating when you write narrative prose is not simply visual. It is a means to record consciousness, which implies all that a character experiences, not just what can be seen (and excludes what a character does not or cannot experience, hence suspense, irony, etc.).
Your task, as a writer, is to come as close to that consciousness as possible. This is why, as I wrote the other day, so much of the actual work of writing takes place in the thinking. Once you're solid on that ground, then you need to understand that the medium by which you represent this experience in narrative prose is language. Not paint or film or colour or light, but the sounds and rhythms and structures and syntax and intertextualities and all the rest of it that language offers. (I'm leaving aside experimental narration here; as I say, in the end, anything goes. Flick through Ulysses to see what happens when the visual elements of prose - the materiality of the book - are exploited for narrative effect. But then Joyce did love the cinema.)
Third person limited, particularly when it becomes close to free indirect discourse, is one of the most effective tools we have to do this. So my advice is to be aware of hopping between heads. Observe the head-hopping, ask yourself what this means for your immersion in your story-world, and, if necessary, push that further into the character's pov. The more you are immersed, the more the reader will be immersed.
And the more you are immersed, the more your technical choices are guided by that immersion. It's a true delight when the words seem to be coming from the made-up person in your head, rather than from your own clumsy brain. Sometimes you find yourself using words you weren't entirely sure were within your vocabulary. That's fun!
And when you're on top of this, go and write a head-hopping story where nobody notices what you've done, congratulate yourself on your technical accomplishment, and tell everyone you can about it.