How can you tell if your child is finding internal satisfaction? I look for signs of contentment, happy, alert, periods of calm and the ability to concentrate. Generally I feel children innately look for activities that bring them satisfaction. Doing purposeful work, bringing pleasure to others, beautifying the environment. 

There is also the need of a child to exercise - achieve a level of metal and physical exertion during the day. The need for fresh air, outdoors, the longing to connect with nature and the world around them. The desire to connect with other beings, perhaps animals and other people. Achieving all of these brings internal satisfaction. 

Otis is singing while is he working. There is something about that too that makes me think this work is satisfying.