The thing about risk compensation is that you're bound to say that, and you're almost certainly wrong. The fact that you wear a helmet says you have already decided that there are some foreseeable accidents in which it will mitigate your injury, and since this attitude is embedded in your consciousness, you are bound to proceed more cautiously if you leave your helmet at home, ergo you ride in a way which carries a higher probability of an accident when you are wearing a helmet, assuming that your attempt at cautious riding is actually effective.
Brilliant kitchen psych. there. Fascinating.