Toddlers are distractible. Their minds flit constantly here and there, and they have a terrible time concentrating on even the most stimulating project. They might be fascinated by a colorful new toy, but only until the next best toy comes along. This can be maddening for parents or teachers, who often try to rein in a toddler's impulsivity.

But should we really be trying to teach self-control? Psychologists are beginning to raise these questions, and some are even suggesting that it may be detrimental to the developing brain to push it toward maturity too soon. University of Pennsylvania neuropsychologist Sharon Thompson-Schill and her colleagues study a region of the brain called the prefrontal cortex, or PFC, the part of the brain that filters out irrelevant information and allows us to focus. It is also the last part of the brain to mature and become fully functional. It lags behind the rest of the brain until about age four.

In the most recent issue of Current Directions in Psychological Science, a journal of the Association for Psychological Science, Thompson-Schill and colleagues speculate that an immature PFC may not be a deficit at all, but rather an advantage in the first years of life. Here's an example: It has to do with guessing. Say you are naïve about the game of football, but you are playing a guessing game: Will the offensive team pass or run the ball? You observe that the team passes the ball three out of every four plays, so you guess "pass" 75 percent of the time and "run" 25 percent of the time.

That's not smart. Smart would be saying "pass" all the time. And if you played this game with your toddler, that is likely what he or she would do. Toddlers are often better at this, because their immature brains are still operating on a brute-force competition between two alternatives: pass or run. They are not yet capable of guessing.

For toddlers, this inability is a good thing, because they can't afford to guess. They have a lot of learning to do, and much of that learning has to do with hard-and-fast rules and conventions. In fact, this rigidity may be essential to language acquisition. Learning language is an intimidating task; it requires saying the right thing in the right context, and agreeing with everyone else that these are the right things to say. It's no surprise, the psychologists note, that kids pick up languages so effortlessly compared to adults.

And it's not just language. Toddlers are mastering all sorts of social conventions that simply must be learned. They're the rules of the world. In this sense, trying to hasten the brain's development may be not only difficult by unwise.