The most critical aspect of any VUI is the user experience. When we speak to someone for the first time, we expect him or her to understand us. For each unique person we encounter, we do not need to be trained on what to say, when to speak, and how to talk—we simply assume the other person speaks the same language in the same manner. These underlying communication processes are embedded in our language and our culture. As long as both parties follow the implied communication rules, any person can effectively communicate with any other person. A good VUI must follow the same underlying communication guidelines—making technology transparent to subscribers by creating a seamless and natural interaction between voice and data.