The next generation of technology interfaces is taking us beyond the inherent limitations of swipes, taps, and clicks with the more nuanced and natural signals of human speech. The design techniques and metaphors of graphical user interfaces (GUIs) simply don’t apply in this new era of voice interaction. The new wave of voice user interface (VUI) design has to be based on conversation—the communication system we learned first and know best.Conversation is a highly complex but systematic medium, with defining principles far more subtle and compelling than grade-school admonishments like “Never start a sentence with ‘And’,” or “Don’t interrupt.” When we interact with other humans, we take the complexity of conversation for granted; it’s already second nature. But when we set out to design a spoken dialog with a device, not understanding the true, inner workings of conversation will result in a frustrating user experience. And because voice is such a personal marker of an individual’s social identity, the stakes are especially high: users of poorly designed VUIs report feeling “foolish,” “silly,” and manipulated by technology, and so they avoid repeat usage. But it doesn’t have to be this way.Here are six rules based on principles of everyday conversation that will not only keep a dialog on track, but will help VUI designers navigate this new era of effortless, human-centered UIs.