Children are naturally curious, and it's very sad to see a child who is so burnt-out on forced education that when presented with something inherently fascinating (like a butterfly on a flower) he won't even bother to look--just remains deep inside his own world. Schools are limited in their ability to allow a child to discover, so education becomes "canned"--predigested and predetermined, not allowing space for the child to find anything out on his own. It sometimes becomes just a guessing game to find out what the teacher has in her mind. We pretend we're doing experiments when really we are just doing demonstrations.
Self-determination theory holds that intrinsic motivation is much more powerful than extrinsic; in other words, doing something that is meaningful to you will have more lasting effects on your life than doing something to satisfy an external pressure put upon you (see "The school that puts kids in charge of their own education" in the side bar). Discovery is central to intrinsically-motivated learning. I think we are too quick to classify activities as "too easy for you" or "too hard for you" -- too easy or too hard for what? What if he wasn't trying to put that puzzle together the way most people would, but had a completely different end in mind? We need to get away from giving the impression that the world has already been completely explored, and now "you can just sit down and learn everything that has already been figured out for you." That is a dead-end--no wonder kids are bored.
If discovery though play is the prime learning modality for your child from early-on, he will maintain a love of learning even when things get difficult. Below are two pictures of my guys a couple years ago; one is discovering how markers can draw (yes, on the wall too) and the other is thinking about the patterns that are made by circles of dots when you draw lines between the dots in different configurations. He crafted a chart from these, and went on to larger numbers of dots before he discovered the rule behind the patterns. All on his own. Not because he's smart, but because he's curious.
