When I was in elementary school, up until age 8 or so, I believed you couldn't consciously think a lie. You could unknowingly think something that was untrue, like if a little kid believed in Santa they could think of Santa as though he was real. You could think "I'll imagine that the sky is yellow". But you couldn't just think "Two plus two is five" unless you honestly believed it or caged it in somehow.

I wasn't clear on what would happen if you tried, but I was sure it was bad.