2014 Prius Dome Lights

Hello, I'm a newbie as I just purchased (well, leased) my 2014 Prius 3 three weeks ago. I love it, although it's a bit of a learning curve considering my last car was 13 years old and didn't even have power locks/windows!

Anyway I accidentally left one of the interior/dome lights on the 2nd night after I got it. My neighbor told me. It was on for 6 hours but my battery was fine. Nothing happened. I have no idea how it got turned on. I must have bumped it I guess.

Today when I was driving to work I had my headlights on. I noticed as I was driving that the dome lights were on. I've been pretty vigilient making sure all my lights have been off when I leave the car due to that initial incident. I have no idea if the lights had been on since the night before or if the headlights made them turn on or what. The dome light switch position is set to off. I turned the lights off but I am worried my battery will suddenly die now. If I left them on last night then they were on for 10 hours.

Basically I'm wondering...do they turn on with the headlights? Is there some setting I'm overlooking? How did both get turned on? I never touch them. Either they're somehow coming on automatically or I'm an idiot and somehow accidentally turned both on.