A friend of mine spends 20 to 30 minutes a day solving Sudoku puzzles. He says it improves his speed of mental processing and makes him, well, smarter.

Hold that thought.

Ask people which factor contributes the most to success and most will choose intelligence, even though science says you also have to be lucky: Right place, right time. Right person, right time. Right idea, right market, right audience at the right time. 

Yet even though there are ways to "create" your own luck, you can't control luck.

But you can control, to some degree, how smart you are. 

Let's Define "Smart."

While there are a number of different forms of intelligence, let's focus on two. Crystallized intelligence is accumulated knowledge: facts, figures. Think "educated."

Of course we all know people who are "book smart" but not necessarily smart smart. That's where fluid intelligence comes into play: The ability to learn and retain new information and then use it to solve a problem, to learn a new skill, to recall existing memories and modify them with new knowledge. Think "applied intelligence."

Becoming more educated is, while not easy, certainly simple.

Improving fluid intelligence is harder, which is one reason why brain games--crossword puzzles, Sudoku, brain training apps, etc.--are fairly popular.  

But do they make you smarter? Do they improve fluid intelligence? 

Basically, No.

A 2007 study published in Behavioral and Brain Sciences assessed the impact of brain training games on fluid intelligence. After participants played Tetris--yes, Tetris--for several weeks, cortical thickness and cortical activity increased. 

Both are signs of an increase in neural connections and learned expertise. In simple terms, their brains bulked up and got smarter.

But after those first few weeks, cortical thickness and activity started to decrease, eventually returning to pre-Tetris mastery pursuit levels--even though their skill levels remained high. Participants didn't lose brain power.

Instead, their brains became so efficient at playing Tetris those increased neural connections were no longer necessary. Using more mental energy was no longer necessary. As with most things, once they kinda figured it out, it got easy.

Unfortunately, no matter how much work it took to learn new information or gain new skills,  "easy" doesn't help improve fluid intelligence. Once knowledge or skill is in your pocket, you certainly benefit from the increase in crystallized intelligence.

But your fluid intelligence soon returns to a more baseline level. 

That's the problem with brain training games. Solving Sudoku puzzles, and only solving Sudoku puzzles, won't improve my friend's fluid intelligence in any other areas. 

It only makes him better at solving Sudoku puzzles.

Learning how to use a new inventory management system will improve your fluid intelligence, until you've mastered it. Setting up Quickbooks for a new business will improve your fluid intelligence, until you've mastered the accounting process basics.

Once you achieve a level of comfort, your brain no longer has to work as hard, and all that new mental muscle gained starts to atrophy.

So what can you do?

Stay Uncomfortable.

Easy: Once you've mastered a new game, a new process, a new skill, a new anything--move on to something new.

At work. At home. Anywhere. Just keep challenging yourself.

Not only will you pocket a constant flow of new information and skill, your brain will stay "bulked up" and forging new neural connections, making it easier to keep learning and growing.

And then there's this: The more you know, the more you can leverage the power of associative learning--the process of relating something new to something you already know.

Not in a Pavlov's dog kind of way, but by learning the relationship between seemingly unrelated things. In simple terms, whenever you say, "Oh, that makes sense: This is basically like that," you're using associative learning. 

The more you learn, the more likely you will be able to associate "old" knowledge to new things. Which means you only have to learn differences or nuances. And you'll be able to apply greater context, which also helps with memory storage and retrieval, to the new information you learn.

All of which makes learning even easier, which research shows will result in your being able to learn even more quickly--and retain a lot more.

So if you like brain training games, master one and then move on to another. And another.

Better yet, keep pushing yourself to learn new things about your business, your customers, your industry, etc.

Not only will that help you become more successful, you'll also get to improve your crystallized intelligence and fluid intelligence--which will surely help you become even more successful.

Where win-wins are concerned, that's a tough one to beat.