The brain releases dopamine as a "reward"; it's a feel-good chemical that contributes to positive reinforcement of various behaviors. People with ADHD have limited dopamine response, which can express as a lack of motivation relative to others.
I thought dopamine was both the anticipatory neurotransmitters and the reward. But the reward neurotransmitters are different, they're your endorphins, endogenous opioids.
If dopamine only happened once you received a reward, it would not cause you to get you to actually act before hand.
It's still hacking the brain if you make the perfect Skinner box and take all their life savings and then some