Most people don’t realize there’s an entire sleep lab that studies what happens when mothers and babies sleep together. At the Mother–Baby Behavioral Sleep Lab at Notre Dame, Dr. James McKenna has spent decades uncovering what our culture often ignores: Co-sleeping is biologically normal—and deeply protective. Here’s what the research shows: Mother–infant pairs sleeping in close proximity show synchronized patterns in breathing, heart rate, arousals, and temperature—fostering better regulation.