It's very simple. You can use one of two methods:
MM's--get paid for what they DO.
ET's--get paid for what they KNOW.
EM's--just get paid.
Or, ask a nuke to add 2+2 and see the answers you get:
ET--will give you an answer of 4.00000000000 EE +0 on his TI graphing calculator
EM--will give you an answer of 4 using pencil and paper.
MM--will give you an answer of 4, pointing at fingers and toes (sometimes).
ELT--will give you an answer of 10, based on 2+2=4, which is close enough to 5, and then rounds up to 10, or simply asks, "What do you WANT it to be?"