Sleep talking might sound funny, but it’s often a sign of something deeper. It starts with a mumble. Maybe a laugh. Sometimes even a full-blown rant. But the person lying next to you has no idea they ...

You wake up to your partner telling you that you had an entire conversation with someone named Bob last night, or your roommate mentions you were giving what sounded like a presentation in your sleep.

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory. She reports on topics from maths and history to society and animals. Katie has a PhD in maths, ...