I recently read the article "The Business of Happiness" by Nancy Cook in the excellent Fast Company magazine.
The article explains how the anticipation of a pleasurable experience feels as good as finishing an onerous task (like a marathon or an exam). They discovered that a meaningful experience such as volunteering often makes people happier than moments of pure pleasure.
Unknowingly, it seems that we have being trying to apply these concepts while raising our children. Kids like to feel happiness through meaningful experience - helping Dad finish an almost impossible job, for example, organizing the garage, or mowing the lawn. Helping mom fix a closet. These are volunteering kind of experiences that will make them feel happy and proud about "helping mom and dad", rather than just a moment of pleasure, like giving them money to buy some candy or an iTunes app.
The article goes on to mention that studies have found that happiness for young people is about excitement and that happiness for adults is about peacefulness. When "selling" an idea, a house rule, it is much better done through this kind of process - believe me, we've tried them all. Playing with a young child in order to get him to fix the bed together before leaving to school is better than yelling at him "go do your bed or else you will be late for school!!!!". It is also generally faster and you make sure it's done.
Playing some music, singing and dancing silly old songs while fixing the dishes is a more playful, joyful and fun way of making them do the dishes, rather than fighting over who did the dishes yesterday and whose turn it is today. All of them will rather have fun at the kitchen with whoever is making this playful time, than go somewhere else.
Happiness is in our hearts; make somebody else happy and you will be happy too!