Well, at a guess I'd say that we would use our own for an example. We can use machines to see where different neurons fire across a human brain, so we can quantify and measure thoughts in a way. This would give us a way to measure the electric currents and use an allegorical chart to measure it against a healthy human brain.

Not an AI expert, and I'm sure there are holes in the logic somewhere but these are my first thoughts on it.