|Porsha is not amused by tales of dogs and foxes.|
Motivation and purpose are key elements of good characterisation. Yes, we need to know who the goodies, baddies and ambiguities are, but we also need to understand what made them that way and what governs their actions.
A mindless psychopath is infinitely more fulfilling as a protag or an antag once we encounter an event that triggered their behaviour, or discover the childhood incident which was a warning sign that all was not well.
It's true of other figures too. When we understand why Mr Darcy reacts to Elizabeth Bennet the way he does, our feelings for him change - he shows complexity and vulnerability, and perhaps a little more swoonability (I'm guessing here).
This subtle reveal needs a light touch, and is best achieved without a surfeit of adverbs. Consider this slice of Flash Fiction* (which I will now hastily make up to order)...
He watched the fly crawl up the chopstick, marvelling at its instinct for survival. Seven times now, and still it found the strength to escape the water in the beaker. The fly was only millimetres from the end before he gently lifted it on to his finger, and then flicked it back to the bottom of the beaker. "Nice try," he smiled. His other hand, palm upwards, held the glistening insect wings he had pulled off at the start of the experiment.
I don't know about you, but that guy makes my flesh creep. However, I also want to know what makes him tick. Maybe if I can appreciate what made him turn out like this I can overcome my revulsion and keep on reading.
Motivation and purpose add layers of depth to your characters. Knowing what drives them, and perhaps what they're running away from, can suggest actions and reactions you might never otherwise have considered. It can be the catalyst for the magical moment when your characters come to life and - as I've discovered twice in my novels - start arguing for their rights or suggest plot ideas.
So, do you know what makes your characters tick, and how to get that across to your readers?