To this day, exactly where curiosity originates continues to confound science. Psychologists have gotten a much better handle on classifying aspects of curiosity, though. The big question remains; does it come from within us, or is it a response to our outside world?
One camp in psychology believes that curiosity is an internal drive that originates within us, much like hunger or thirst. This drive theory of curiosity sees curiosity as a naturally-occurring urge that must be satisfied in a very similar manner to how we satisfy our hunger by eating. When our curiosity becomes aroused, we look to new or old interests to satisfy the urge.
The drive theory helps explain curiosity-seeking behavior. It shows us why we actively look for and engage in crossword puzzles or take up a musical instrument. Not only are these activities inherently superfluous, they also contain the risk of failure. Viewed as food for our curiosity, however, they make much more sense.
What drive theory doesn't explain is how object-specific curiosity may be. This is where incongruity theory comes in. This theory is based on the idea that our curiosity is motivated when we're presented with something that doesn't fit into our understanding of the world. We tend to view the universe as predictable and orderly; under incongruity theory, when this order is challenged, our curiosity is aroused. Imagine that while you're reading this article, a pencil on your desk spontaneously moves two inches to the left. This doesn't really fit into our worldview -- pencils aren't supposed to move on their own. Can you imagine not looking around the desk in an attempt to explain why the pencil moved?
In this case, our curiosity was aroused by an external event and we were moved to understand it, which supports incongruity theory.
That said, neither drive theory nor incongruity theory can fully explain curiosity. Each one has trouble fully accounting for one aspect or another, which means that curiosity remains a mystery to us. This doesn't mean we haven't arrived at some real conclusions about it, though. The debate over whether curiosity originates inside us or is a reaction to things we encounter in life has little to do with how the concept is classified.