I remember visiting the Caverns of Sonora in Texas. At the lowest point, the tour guide turns off the light for the group to experience what the cavern is like - dark, with the occasional drip of water. The odd thing was that the group I was with was pretty quiet until the lights went out... and then they went berserk with chatter. It didn't seem to be out of a sense of disquiet in the dark though, but had more a sort of "teacher's not looking" feel to it.

I have had similar experiences while exploring caverns in the Ardennes in Belgium. This was actually late eighties, so not as prevalent with smartphones.

The tour guide said all the guides had a running bet which group could stand the longest being in total darkness without using watches/torches/lighters to create some resemblance of light. "Never had a single group last over 5 minutes".

They probably also had that "bet" to be able to give their groups a reason not to immediately turn on a light in the dark. It's very distracting and ruins the experience.

On a smaller scale I see inexperienced campers seem to be dependent on using a flashlight for EVERYTHING when the sun goes down, even when just sitting doing nothing, or performing a task (like walking in a field) that could be done by moonlight.

We have to train this instinct out of ourselves.

It's also just reinforced by biology. Use a flashlight once or twice and until your night vision recovers if you need to do something else your eyes aren't ready to so you need to use the light again... repeat all night.

Red lights work rather well in cases like that.

True but that's not a standard feature for cheap lights or headlamps.

At Mammoth Cave in Kentucky they turn off the lights on every tour. On one tour, my guide turned off the lights and seemed to lose track of time. He started talking about different things, meandering into other topics, without turning the lights back on. It lasted 9 minutes, according to my watch.

The first couple minutes were nothing special, and I was still fully aware of the group of people around me. After a few minutes I noticed a faint light. I don't know if it was a distant tour light around the corner, or if I was hallucinating. I spent a couple minutes looking and trying to figure it out. Around that point I became really uncomfortable, and my heart rate increased as it went on.

My natural reaction would be to close my eyes - if they're closed then surely I'll be immune from the effects of darkness. But this actually increased my anxiety. When it's pitch black there's no visible difference between having your eyes open or closed. It feels like your eyelids aren't working, like the muscle movements are not happening.

It caused a retreat into my own mind. Despite there being twenty people nearby, I felt like they weren't real. It didn't help that the group was quiet, with only occasional shuffles and murmurs coming from them. I started to think they could all walk off, leaving only me and the rambling tour guide. I had a strong urge to light up my watch or phone, but I didn't want to be "that guy". My eyes felt like they ceased to exist.

By the last couple minutes I stopped pondering and noticing things, and started waiting for the guide to turn the lights back on. I think the rest of the group was going through the same thing, judging by their silence. I was surprised at how quickly things returned to normal after they came back on. I had felt like I was near a breaking point of some sort, but within seconds I was fine.

>The coolest part was when they turned the lights off and locked the door.

I'm slightly concerned that the door has a lock in the first place.

Was it locked from the inside or outside? I can see the latter being consistent with Microsoft's style. :)

Probably both. Locks are to keep honest employees from having sex in your anechoic chamber.

>Was it locked from the inside or outside?

I maintain this is a legitimate question.