way to think about it is the change of activation pattern which is a second sigma prime is the activation pattern and sigma prime prime is how much those change in some measure the Hessian is a border one over the has seen itself without the Hessian you don't care about the Hessians movement while you carry we are worried about is a gradient moving a lot because that means your feature scheme is moving a lot you want to ensure the feature scheme does not move so you need about the size of the movement of the feature