One of the biggest frustrations when working with teenagers is the “Why did you do that?” factor. After all, by the time they’re teenagers, they often look and talk like fully functioning young adults. So we often expect them to act like that too. But when a teenager does something that seems so incredibly unreasonable, we’ll wonder, “Why did you DO that?!” Of course, we're often disappointed that they simply can't provide a good response.

The reason is because a teenager’s brain is still under construction. In fact, this period of adolescence is the second biggest period of brain development, only after those first three years where the brain is expanding at an alarming rate. So, though teenagers may look and even talk like young adults, their brains are not always caught up.

Two separate things are happening during the teenage years: 

1. Changes in brain structure – the size of different areas in the brain

2. Changes in brain function - the parts of the brain that complete different tasks. For instance, we know that teenagers may use different parts of the brain than children when performing the same task.

As children become teenagers, the brain begins to modify the networks that connect different parts of the brain. As a result, it gets rid of connections that are infrequently used. This is called “pruning of grey matter”. Essentially, use it or lose it. Through this process, the connections that are most commonly used grow, and the connections that are infrequently used disappear.

One way to visualize this is to think of a meadow between two patches of forest. As people travel from one forest to the other, they cross the meadow. In the beginning, there will be any number of small paths that can get people from one side to the other. But as people figure out the most efficient way and begin to all follow the same route, a small path will appear in the grass. This path will grow over time, and the other small paths will eventually fade away. That’s what the pruning of the brain is like.

So clearly there’s a lot going on in the brain of a young person. And we know that the prefrontal cortex (that’s the part that makes decisions and does complex thinking) is not fully formed until around age 25. When we ask teenagers, “What were you thinking?” we may find that, in fact, they really weren’t. At least not logically.

This can definitely be frustrating when working with adolescents. But it’s very important to remember. Because so often we find ourselves blaming hormones or determining that a child is stubborn or difficult. And when we can think about a teenager in the context of a brain under construction, we can be much more thoughtful about how we approach them, and how we make sense of the work.