How we stumbled upon the rat play vocalizations: A recollection

Over a quarter of a century later, most rodent researchers know that specific types of rat Ultrasonic Vocalizations (USVs) appear to index distinct affective states endowed with arousal, value, and motivational force. Few know the story, however, of how we accidentally stumbled upon 50 kilohertz (50 kHz) USVs in the context of rat play by turning the wrong dial on a bat detector, which I recollect here. The tale of that mistake highlights the critical roles of serendipity, preparation, openness, persistence, and a supportive environment in scientific discovery.