Puzzled by Puzzles

It has been interesting to watch Quinn try to figure out puzzles. He is very good at removing pieces of course, and will now attempt to push them back in. He usually still needs quite a bit of help rotating the piece in the right direction.(unless its a circle!)
I've been told and have read that puzzles are an incredibly imporant learning tool....equal to books, even.....so needless to say, we are big puzzle fans here. I like the old wooden ones....I buy most of them on Ebay.
Here he is with one of his truck puzzles. He knows to turn it over and stick his finger in the hole to get the piece out....

Out comes the piece...

But getting it back in is a little harder....