Reality Checks- Why do they work?

I never really thought about it but it just struck me. If lucid dreams replicate reality so well, why can I breath through my pinched nose or put my finger through my palm?

You know you are dreaming and that everything around you is just a thought. You un-attach yourself from the preconceptions you have made to things in reality.

Because your real body is breathing, not your dream body. You can't do anything in a dream to stop or change your breathing.

that makes sense I guess
can anyone explain the finger through the palm rc, or the lightswitch one

The breathing one is the only one I would trust. The lightswitch one only works because lightswitches usually dont work in dreams idk why. I guess the finger through palm one only works if you think it will work.

Some say that the light switch one works because it is difficult to alter how light scatters. Where you are sitting, look around the room. See how different parts of the same object look different because of the amount of light hitting them? I haven't had enough experience LDing to say for sure that it is difficult to change light, but it is apparently hard enough to use as a RC.

yap. breathing with your nose n mouth closed always was my number one RC. ^^ hes 100% safe, i think.

The breathing reality check works because when you control your breathing in a dream, you control the breathing of your actual body. Holding your breath in a dream means you hold your breath in reality.

A few reality checks work like this; by using elements of human physiology that are still relayed during dreaming. Quite a few reality checks however (such as the finger-through-palm one) work by expectation.

The light switch one is different; I've had a light switch fail despite me expecting it to work, and being extremely surprised when it didn't (though I easily changed the lighting level myself by thinking it, disproving yet another myth). I think it's been suggested that this is due to a part of the brain being deactivated during sleep.

The breathing test is ideal for a RC as it will always work as it's supposed to (unless you actually can't breathe but then you have bigger problems!).