Question: How do you know what’s inside someone’s brain?

Jason Ellis answered on 7 Nov 2018:

Hi Ale251 – Well, the way I do it is I put 7 sensors on an individuals’ head, 1 by each eye, 3 on the chin and 1 behind each ear…sounds like a lot of work and it is!! What this does is measures the electrical activity in the brain and is called Electroencephalography (EEG). What we can see from EEG is the speed and frequency that the brain is working at and we know that a certain speed and frequency is associated with being awake whilst other patterns in speed and frequency can tell us what stage of sleep someone is in and whether they are dreaming or not. It is pretty cool to watch!