Question: When you say 'what is going on in their brain', do you mean what is happening physically, or emotionally/mentally?

Rebecca Dewey answered on 15 Jun 2015:

We can measure what’s going on in the brain in different ways. We measure the electrical activity caused by brain cells sending messages, or we can measure the amount of blood flowing to the area. The idea with this second one is that if a part of the brain starts working, it will demand more blood (more oxygen, more energy) to support its work. So I measure what’s happening physically at the very moment they are there in front of me. However, you can also look at changes that are caused long-term, like certain areas of the brain getting smaller or larger as they are used or developed. We can also look at the connections between areas of the brain and look at how thick and strong they are.