> but this study says nothing about the quality or intensity of the early birds vs. night owls. Yes it does. Sleep length was fixed at 8 hours, and they acquir

> but this study says nothing about the quality or intensity of the early birds vs. night owls. Yes it does. Sleep length was fixed at 8 hours, and they acquired polysomnographic recordings of both nights spent at the lab and scored the sleep quality. ==> No statistical difference. They controlled most controllable parameters. Read the paper and the supporting materials.