What is not interesting is just jumping to the conclusion, and showing the results of the change without showing the process of the change.
This comes up a lot in discussions around portrayal of characters. I've been criticised at times, and had the criticism of other authors, that occasionally characters seem unbelievable because they do something, "out of character." The author's comeback is inevitably, "well, they changed! Isn't that the whole point of character growth?"
Yes and no... character growth does involve changes, but you need to bring the reader along on the ride. The reader doesn't just want to see the results of a change, they want to be there, pace by pace with the character as that character transforms.
Mark Kennedy, an artist and animator whose work I admire, wrote that the essence of humor is watching a character think. He cites the moment in classic cartoons when an animated character runs off a cliff, keeps running, slowly looks down, sees nothing underneath him, starts to look back up (legs still pumping) and then suddenly does a double take, eyes bugging out as he finally realizes he's about to fall. Only then does the character plummet downward. That moment of watching the character realize the predicament they're in, is the essence of the humor.
I would take this a step further, and say that watching a character think is the essence of drama as well.
Here's an example: imagine a supporting character shows up in one scene trying to help the hero, and shows up in the next scene trying to kill the hero, then (without any explanation), shows up in a still later scene trying to help again. Pretty wierd, right?
Now recall the moment from Buffy: The Musical Episode, when Spike, sitting alone, smoking and brooding, sings, "I hope she dies, I'm free if that bitch dies," then, tossing his cigarette away and standing up, immediately follows this with, "I better help her out."
Not only is that moment hilarious (called it, Kennedy) but it takes you into Spike's mind. You see the conflicting desires that rage in his heart, but what tells is the one that comes out on top in the end. It's a great moment of internal conflict. However, if he had acted on those words and *actually* tried to kill her, then turned around and tried to help her, that would have been wierd and deeply off-putting.
Another example is described by Kennedy in a recent post (go about halfway down to the part about the Detectorists) where he describes a quick series of shots that takes only seconds, but show the process of a character thinking and changing. A guy starts lonely because his girlfriend has moved out. While taking out the trash, he finds a positive pregnancy kit. There's a shot of his face, showing how much this rocks him. Then it cuts to a shot of a half-empty bottle. Then it cuts to him leaving a voicemail for her saying how much he loves her and wants her back.
If we hadn't been there along the way, seen the pregnancy kit, the shock, the alcohol, the implication of time passing due to how much of the bottle he's drunk, then the transformation in him would be strange to the point of being nonsensical. But we do have those things, and so you're there with the character as he transforms, you see the time it takes for him to come to this decision (the bottle's half-empty; he must have spent time thinking about it) without having to take all that time yourself (we don't have two hours of him drinking on screen, just cut to a half-empty bottle.)
All too often I see moments in movies or books where suddenly a character is behaving in a way that is very different from what I would expect, knowing them as I do. Once in a long while this can be used to great effect, to build tension (why is she doing this all of a sudden?), but that has to be used a special way: rarely and with a huge and unmistakeable change. Much more commonly it's a slight dissonance which leaves you feeling like maybe you just didn't know the character as well as you thought, and that detaches you from the character, and by extension, from the story.
The point is, when you're writing a character's transformations, don't show the change in action until you show the change in thought. Give the reader insight into the character's heart and mind as it changes. Only then will the change in action make sense.
As Kennedy says, cut to the face, and show the audience how the character is reacting.