Every kind of emotion in a novel can fit on a graph. There is the climactic curve, which should increase steadily to each climactic point in the novel, fall and then begin building again for the next climax, like the 1812 Overture. And the G/I curve, which Kurt Vonnegut introduces below (which, combined with some beta reading I've been doing got me thinking on the subject).
Those are macro-curves, which detail an entire story, but each character should have their own emotional curves within scenes. For instance, in the first draft of Aetherstorm, I had Konrad running in fear of his life. He accidentally stumbled into a party and ended up fighting a sort of swashbuckling duel with one of the guests, complete with witty repartee. It was a great scene, but it stood out like a sore thumb, because people who are fleeing in panic don't suddenly collect their wits, pass some urbane banter and finish their opponent with urbane wit.
Which made me think of how emotions, and character development intertwine in the greater picture. Some emotions, such as fear, play out in a curve within one sequence and then after a few minutes, hours or days, the emotion is forgotten. Other emotions get reinforced by ongoing experience. The writer becomes more and more frustrated over time as he continues to face rejection (not speaking from personal experience or anything :P ). The grieving father who turns to alcohol only drives himself further into depression. If there is nothing inciting the emotion to change it will carry-on in a fairly smooth and predictable manner, only jumping erratically when something significant to that emotion comes along. Grieving father finds out it was all a mistake and his son is alive after all, or the writer catches his big break.
I think it's these bigger emotional curves that define characters and character development and having predictable emotional curves is what defines a character we can all fall in love with.
Maybe that's all obvious to some people, and maybe it's been said before, but that's what I learned about writing this week.