Dogs prefer more than just the reward

From Pacific Standard: “New research by … the University of Agricultural Sciences, Sweden, investigates whether dogs enjoy the experience of solving a problem in order to obtain a reward, or if it is just the reward itself that makes them happy. … The results show that when dogs solved the problem and earned a reward, they wagged their tails more and were more eager to repeat the experience than if they were just given a reward. The study also found that food was a preferred reward over time with another dog and petting from a familiar human.”