But I don't understand why the Lizard Brain only works in some instances and not others.

When I was a kid, I used to climb my father's ham radio tower, and it didn't bother me a bit. But I've never leaned out of high windows, and don't even like looking down from one. But from 30,000 ft, the ground just looks like a really good map, and with a good book I can stifle my thoughts that there is NOTHING holding the plane up but air.

Why some times and not others?

Sue