Asking questions is a deeply human experience. All human languages have a way of posing questions, including those that can be answered with yes or no, known as polar questions. The meaning of these utterances feels as undebatable as their conceptual primacy. One interlocutor describes a possible scenario in a form that requests a response, and the second interlocutor, by answering yes or no, tells them to the best of their knowledge if that is the case or not. As such, the formal meaning of polar questions, the “code” that returns "did you vote" if you enter "you voted", seems nothing other than a primitive logical operation that is conceivably identical across languages.

However intuitive it seems, a singular core meaning is at odds with the observed empirical complexity. Polar questions may encode nuanced meaning components such as bias and usage restrictions, and have diverse expressions in the morphosyntax and intonation. Languages do not behave in a uniform manner in these respects, either. While the sporadic research on languages beyond the few most widely studied languages have confirmed some components of our understanding of polar question meaning, they have also introduced a staggering range of novel nuances, clusterings between them, and unexpected structural correlates. How can languages create such rich and varying paradigms of nuances and form-meaning correspondences out of a simple shared logical operation?