What is Constructive?

I recently started reading Why We Do What We Do by Edward L. Deci.  Page 18 contained a couple of paragraphs that had me wondering.

Harlow placed monkeys, one at a time, in a cage that contained a kind of puzzle.  They would figure out how to open it; then how to close it up again. And they would repeat their actions many times. There were no tangible rewards for the behavior, and yet these naturally inquisitive monkeys were focused and determined. What's more, they seemed to be enjoying themselves. Harlow used the term intrinsic motivation to explain why the monkeys had spent many hours working on the puzzles, where the only possible "reward" seemed to be activity itself.

Although it's important not to go too far with animal-human comparisons, the spontaneous, though clearly constructive, behavior of those monkeys inspires one to think about the similar behaviors in young children.

As soon as I read the last sentence I asked the question of this post's title, "What is clearly constructive behavior?"  A quick Google search defined constructive as, "Serving a useful purpose; tending to build up."  Obviously the author has a different definition of constructive in mind than myself or Google.  I would not consider wasting hours on a puzzle very constructive.

If what he means is that the activity was, "seemingly enjoyable" to the monkeys I would not have anything to disagree on.  However, constructive?  I don't think so.

This is something I find myself questioning quite often.  Can I create enjoyable activities that are also constructive.  To me the answer is an easy yes.  Reading, working out, eating good food, getting enough sleep.  These are all quite enjoyable and constructive to me.  

It also gives me a simple check on how I spend my days.  If I am engaging in activity that is neither enjoyable or constructive I immediately move on.  If it's enjoyable but not constructive, I see if I can make it constructive or find another activity that is equally enjoyable and constructive.  The same goes for activities that are constructive, but not enjoyable.  By finding the sweet spot where both exist concurrently, I am able to constantly live a life of improvement without sacrificing my own happiness.