This dissertation challenges the standard view that fifteenth-century poets wrote irregular meters in artless imitation of Chaucer. On the contrary, I argue that Chaucer’s followers deliberately misread his meter in order to challenge his authority as a laureate. Rather than reproduce that meter, they reformed it, creating three distinct meters that vied for dominance in the first decades of the fifteenth century. In my analysis of 40,655 decasyllables written by poets other than Chaucer, I show that the fifteenth century was not the metrical wasteland so often depicted by editors and critics but an age of radical experimentation, nuance, and prosodic cunning. In Chapter One I present evidence against the two standard explanations for a fifteenth-century metrical collapse: cultural depression and linguistic instability. Chapter Two outlines an alternative framework to the statistical and linguistic methods that have come to dominate metrical studies. In their place I propose an interdisciplinary approach that combines the two techniques with cognitive science, using a reader-oriented, brain-based model of metrical competence to reframe irregular rhythms as problems that readers solve. Chapter Three applies this framework to Chaucer’s meter to show that the poets who inherited his long line exploited its soft structure in order to build competing meters; in that chapter I also argue that Chaucer did not write in iambic pentameter, as is generally assumed, but in a “footless” decasyllabic line modeled on the Italian endecasillibo. Chapter Four explores metrical reception; by probing scribal responses to Chaucer’s meter we can gain insight into how fifteenth-century readers heard it. Chapters Five through Seven investigate three specific acts of reception by poets: those of John Walton, Thomas Hoccleve, and John Lydgate. I conclude the dissertation by tracing the influence of Hoccleve and Lydgate on the later fifteenth-century poets George Ashby, Osbern Bokenham, and John Metham, and by identifying the eclipse of fifteenth-century meter with the Tudor poets Stephen Hawes and Alexander Barclay, who replaced a misreading of Chaucer’s meter with a misreading of Lydgate’s, inadvertently returning sixteenth-century poets to an alternating decasyllable reminiscent of Chaucer’s own meter. / text