One way that happy couples are alike? Synchronized alarm clocks -- and bedtimes. A study published this month in the journal Sleep revealed that how couples sleep together is influenced by how satisfied they are with their marriage. The 46 participating couples reported that those who shared a bed were simultaneously awake or asleep in it about 75 percent of the time. When wives felt higher satisfaction in their marriages, that number rose, as they synced their sleep patterns even more closely with their husbands'.