I’m much better at controlling myself now than I was when I was a kid. I’m more organized and less impulsive. Why is that? What happened in my brain to make this happen?

A study published yesterday in Current Biology could have a clue. Scientists studied the changes that happen in the brain as kids become adults. During this process is where they, hopefully, also become much more well-behaved. In a sense, scientists analyzed the physical changes that occur as “executive function” — the set of skills associated with greater discipline and focus — develops. Executive function skills are crucial; they play a role in everything from drug use to how much education a person completes.

The University of Pennsylvania team analyzed the brain scans of 882 people ages 8 to 22. (Their brains were imaged as part of a separate study of brain development.) By comparing the scans of younger brains with those of older brains, they saw two big changes. First, as the brains aged, different parts became segregated into “modules” that work more closely together.

But even though the brain was segregated into specialized modules, it wasn’t becoming fragmented. The brain overall was becoming more integrated because the connections between the modules were getting stronger.

These findings provide more insight into how the brain becomes more complex. It could be potentially helpful for diagnosis: now that we know how a normal brain develops, it’s easier to see if a brain isn’t developing the way it should. Next, the scientists are studying whether this new information can be applied to help predict which children are likely to develop psychiatric disorders.