What are reward prediction errors?

Reward prediction errors are when your brain surprises you with something better or worse than it expected.

Imagine you're playing a game where every time you press a button, you get some candy. At first, you don’t know how much candy you’ll get, sometimes 1 piece, sometimes 2, sometimes even 3! Your brain is trying to guess how many pieces of candy you'll get each time. A reward prediction error happens when the actual number of candies doesn’t match what your brain thought.

Think of it like a cat waiting by the door for food. If the cat expects a small treat and gets a big plate of food, it’s super happy, that's a big reward prediction error in a good way. But if the cat expected a big meal and only got a tiny snack, it might be confused or even a little sad, that's a reward prediction error in a not-so-good way.

Your brain uses these surprises to learn what to expect next time. It’s like when you try a new ice cream flavor, if it tastes better than the last one, your brain pays more attention to that flavor for next time!