I remain convinced that you can never quite know all the things a child is learning at a given moment or through a given activity, as learning is an unspoken and unseen process of the brain, but some of the pointed out benefits of simple wooden blocks include manual dexterity (the skill and control of the hands) and eye convergence. Lots of science and problem-solving can be learned as you get to experiment with the rules of gravity, balance, and physics. Creativity and imagination are a high point as you are transformed into a mini-architect.
But of course, there I am trying to break everything down again and figure it all out.
Nonetheless, he enjoys playing with blocks just as before, and is up to building 15+ high towers now. He gets quite frustrated when he doesn't balance them right and they tumble to the ground. But here he is, extremely thrilled with himself that he finally built a stable tower. Once he got it stable he kept changing the top, adding more rectangles and then some triangles or semi-circles, until he had emptied the bin of blocks he had out.
"And they said, Go to, let us build us a city and a tower, whose top may reach unto heaven; and let us make us a name, lest we be scattered abroad upon the face of the whole earth."
Hunter is 3 years, 3 months old