For example, if you meet someone and you handshake. When the other person presents his hand, you automatically shake his. It is something you have learned and that now, you don't have to think to do it anymore. It is automatic.
What If I present my hand for a handshake, but instead of only shaking it, I grab it and put it in my face. You will be confused because this isn't usually what you do when you handshake! This is an interruption of an automatic behavior.
Are you into hypnosis?