Let's look at some examples:
- Visual scenes: The more time you spend looking at a landscape, an interior space, or a painting, the better you are able to predict it. At first you aren't able to predict the spatial relationships between elements, but after some time it becomes easy.
- Logic and word puzzles: After expending a certain amount of mental energy, uncertainty is reduced, and the puzzles disappear.
- People: At first, strangers can be unpredictable. The more you interact with a person, the better you understand him or her. It becomes easier it is to predict his or her behavior. (Most people's personalities are moving targets, though, so it isn't possible to reach a state of completely accurate prediction.)
- TV shows: The more you watch a certain show, the better you are able to predict subtle interactions between characters and high-level plot elements.
- Sports and music: Learning new motor behaviors (like new sports, new pieces of music, and new musical instruments) requires a lot of attention. It takes effort to coordinate muscle movements into desired patterns. Over time, though, repetitive training produces smooth, synchronized motions with little effort.
- Cooking: The more brain-time you invest, the better you understand how ingredients interact, and the better you can predict what things will taste like.
- Investments: At first you have no idea how stable various markets are. Over time, your uncertainty is reduced, and you can make well-informed decisions based on past experience.
Even though most of our brain structures function in parallel, the whole attention system is a serial mechanism. Think about it. You can only focus on one discrete thought at a time. Try looking at a complex scene or object. You are able to look at the whole thing at once, but you can't attend to more than one component at a time. Right now I'm looking at a house plant in my living room, and I can't simultaneously think "plant" and "leaf." I have to focus on either a small part or the whole thing. It's complicated because you can think of similar sets of objects at a time ("all the books on my bookshelf"), but you're still limited to a single discrete thought.
Imagine your attention system constantly switching among various thoughts. It spends some time working on a crossword puzzle, switches for a half second to think about what to have for lunch, switches back to the puzzle, switches to the sound coming from the radio for a bit, switches back to the puzzle... Every time attention shifts, it starts applying mental force to a new mental object, moving it a little bit across the spectrum from unpredictable to predictable.
The point here is that we all have a similar (within an order of magnitude) amount of mental energy available to us per unit time. Since birth we have all expended a similar amount of this energy on something. So everyone must have some kind of hidden talent related to those things that occupy most of his or her thoughts.
(The whole idea of "useful" mental work is another story. Utility can be defined in a variety of ways. A common one might be something along the lines of "the good of the many." If a person's goals are aligned with the utilitarian viewpoint, he or she would spend his or her mental energy on problems that benefit the most people. If the reward hypothesis is correct, we spend our mental energy on those things that we expect [based on previous experience] will bring us the most rewards. This gets into the whole area of motivation, which is beyond the scope of this article. To attain the highest level of utility, however it is defined, it is probably necessary to spend time thinking of ways to improve one's own thinking abilities, or metalearning.)