Motivation-Reaction Units

Note: This is the third installment of our scene structure series. While this article will still make sense if you haven’t read the first two, I suggest going back and reading the posts on Scene and Sequel for better understanding.

Motivation Reaction Units

Motivation-Reaction Units: The building blocks of fiction.

If “Scene and Sequel” are large-scale scene structure, then “Motivation-Reaction Units” are small-scale scene structure.

At the beginning of the month, I led a workshop on Writing Great Scenes. As I was explaining that the “Sequel” is the reaction to the action sequence in the “Scene” (more on that here), one of the attendees said that she found it difficult to differentiate between the two, because it seemed like the characters were reacting to things throughout the Scene itself.

And she’s right. Characters – and humans in general – react to stimuli all the time. When your brother pops out from around the corner in a monster mask, we first scream and run away in fright, then get angry and punch them in the nose.

They, in turn, react to that punch by yelling for mom.

This is the core concept behind the motivation-reaction unit (MRU), and it’s the basic building block of fiction.

What is a Motivation-Reaction Unit?

The completely horrendous term “Motivation-Reaction Unit” was first coined by Dwight V. Swain in his fiction-writing manual Techniques of the Selling Writer.

The basic concept is that something – the motivation –will cause something else – the reaction – to happen. Cause and effect. It’s not quite that simple, however.

The Reaction

As this article from says, the reaction is made up of up to 3 distinct parts:

  1. (involuntary) feeling
  2. (involuntary) physical reflex
  3. (voluntary) action and/or speech

Note: The distinction between involuntary and voluntary is my own addition, which I will explain in a moment.

You don’t need to have all three of these parts, but it’s generally accepted that they need to happen in this order. I don’t necessarily agree with the fact that the feeling needs to come before the reflex, in fact, many of the texts I’ve looked at have the physical reflex come first. However, it is important that the involuntary action comes before the voluntary action, which is why I made that the distinction above.

Let’s look at an example, shall we?

Janet walks down the hall towards the kitchen. Tacos or leftover burgers for lunch? She muses to herself.

As she passes the bathroom, a monster with black eyes and fangs dripping with blood jumps out from behind the cracked door.


Janet screams, and runs back toward her bedroom, but before she gets there, she hears the monster laughing.

She turns around to find her little brother, Brad, shrieking with laughter, holding the monster’s head by its green hair. A mask.

Her face grows hot. Without thinking, she rears back and slugs him on the shoulder. “You little jerk!” she yells.

“Ow!” Brad rubs his shoulder. “I’m telling Mom!” He darts down the hallway toward their parents’ bedroom.


Motivation: Brad jumps out from behind the door wearing a monster mask.

Reaction: Janet screams (involuntary) and runs away (involuntary.)

Notice that this reaction only includes the involuntary responses – remember, you don’t need all three. Also note that Janet’s reaction serves as a motivation for Brad’s reaction:

Motivation: Janet screams and runs away.

Reaction: Brad laughs (involuntary.)

And so on:

Motivation: Brad laughs.

Reaction: Janet gets angry (involuntary) and punches her brother (involuntary), and calls him a jerk (voluntary.)

How Can Motivation-Reaction Units help my writing?

Having well-constructed Motivation-Reaction Units will help your writing flow better and make your characters’ actions seem more plausible.

It’s also worthwhile to make sure that your characters’ reactions are in-line with their personalities – how they react to different situations is a great way to show your readers who they are without tedious backstory. Just be sure you don’t have one of them do something that’s out of character just to make something in the plot happen. If they hate cats but pets one after it jumps on their lap, well, that’s inconsistent.

Characters are not puppets.

I will say that 90% of what you write is probably already set up in MRUs, simply because the principle of cause and effect guides our entire reality, and therefore our fiction, as well. For that other 10%, you might get the feeling that something isn’t working, but you’re just not sure what. In these instances, it’s worth it to check for MRU-structure.

Should Motivation-Reaction Units make up our entire text?

According to, your text should be comprised entirely out of Motivation-Reaction Units.

It’s certainly possible to do this. However, it’s not 100% necessary. Many books will start out with some description to set the scene that cannot be classified as an MRU, and it works out just fine. The trick is to not overdo it. How much description you give will depend on your genre and what pace you’d like your story to move along at. Thrillers, for instance, will probably have no more than a few sentences of description, while epic Fantasy might spends pages and pages on it.

So, here’s your homework. Open your favorite book to a random page and see if you can identify the Motivation Reaction Units. If you feel that there are sections without any, do you think it would have been better if it had them?

Resources and Further Reading

Techniques of the Selling Writer by Dwight V. Swain (book)

Writing the Perfect Scene by

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H. Duke
H. Duke writes fantasy, horror, and more. Her works include the weird west / urban fantasy serial mashup, Jeremiah Jones Cowboy Sorcerer and the Christmas horror collection, Things on the Shelf: Three Tales of Christmas Terror, as well as the forthcoming Pagewalker series. She wrote the first season of Jeremiah Jones Cowboy Sorcerer while living in Arizona with her husband, Giru, and a shiny black dog named Jupiter. To see what she's up to now, visit her website.

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