The University of Canterbury’s Origins of New Zealand English project, which Hay was first involved with as a postdoctoral fellow, showed that it took only one generation for a unique dialect of English to emerge. New Zealand’s first speakers of English arrived with a variety of dialects, but their children were heard speaking with what was disparagingly called a 'colonial twang'. New Zealand English has since been the site of a lot of linguistic theory – it is the only variety for which recordings are available that cover its entire history, allowing a unique insight into how dialects and accents develop and how sounds change over time.
Now Director of the New Zealand Institute of Language, Brain and Behaviour, Hay’s research straddles sociophonetics, laboratory phonology and morphology. Much of her work explores how our past experience with words and sounds affects how we produce and perceive speech. Her work has shown that that the way we speak and listen is highly context-sensitive, and can be affected by subtle environmental factors such as where we are sitting, or what else is in the room.