A 16th-century physician wrote that many laborers dozed off exhausted at the start of each night; sexual intercourse with their wives typically occurring in the "watching period", after a recuperative first sleep. Anthropologists find that isolated societies without electric light sleep in a variety of patterns; seldom do they resemble our modern habit of sleeping in one single eight-hour bout. Much has been written about dream interpretation, from biblical times to Freud, but sleep itself was historically seen as a passive state of not-awake.