Question: What is it about the positive and negative voltage across a human head that gives you insights into how children learn, and how does an electronic cap measure this voltage?

Tim Fosker answered on 21 Jun 2011:

Hi @snakeman

A cap of receptors measures the voltage across the head in the same way you measure the voltage of a car battery. The electrical ‘potential difference’ is measured between one receptor on the head (called the reference) and every other receptor on the head.

Lots of experiments have shown that the change in positive and negative voltage at different times after something has been observed or a task has been performed reflect different mental processes. For example if you listen to a sequence of sounds with a odd sound occurring very rarely you will be able to spot it and press a button 600 milliseconds after it starts (if you are very fast, most people would be much slower than this), but your brain has already detected the difference between 100-200 ms after the sound began. A change in the voltage of your brain activity for the rare sound as compared with the sound that was presented all the time reflects this.

I hope that made sense? Thanks for the question.