Well-timed rewards and praise are the basis of most training.
But not all learning is accompanied by rewards, is it?
For humans, domestic animals, and even wild animals, powerful aversive experiences also educate.
A fox may get a ripped muzzle, a cow a shock from an electric fence, a horse a mouth full of nettles, a young man a police arrest or black eye.
Live and learn. Such is life.
This mornings edition of The Daily Mail has a nice visual example in an article entitled, Pecking order: Jackal is nipped on the nose after trying to snatch hungry vulture's scrap of meat.
See the whole array of pictures at the link, but the money shot is below: aversive training in the wild.
A bite on the nose: lesson learned!