They can understand in the same way you or me can understand how we are 'supposed' to feel when presented with a situation. Like I said, I may be completely wrong. He also mentioned a head injury when young which may explain a lot. In any case he is clearly a brilliant man. I was stunned at the plastic rendering of the vascular system. Proper, interesting tv, everything about it was class. Even showing the making of the cross, from the first chop of the axe to the end product. I even delayed homeland a night just to watch this all the way through