Sensory Deprivation

Ideally, our senses shouldn’t lie to us. We build mental representations of the objective world – beliefs – from the information our senses feed us, so if that information doesn’t accurately reflect what’s out there, the fidelity of our mental models is compromised from the beginning.

I used to explore caves with a group of amateur spelunkers. One time I split off from the group and went far enough down a side branch that I could no longer see their lights or hear them. I turned off my headlamp and sat perfectly still.

Above ground, we never experience complete darkness. Even with the shades drawn on a moonless night, there’s always some residual light passing through our eyelids. And even on a still night in the country with no crickets chirping, it’s never perfectly quiet, either. There’s always some ambient sound, however faint.

The first thing I was aware of was the sound of my breathing. I muted it as much as I was able, and then I could dimly hear my heart beating. Denied external stimulation, my body turned to listening to itself. Behind those barely-audible sounds was steady background noise – faint but unmistakable, like the hiss from a distant fan, joined by (or fusing into) ringing in my ears. Sitting in a chamber hundreds of feet below the surface and insulated by millions of cubic feet of limestone, I knew that noise wasn’t really there, but I heard it anyway.

The darkness didn’t last long, either. Within a minute or two I was seeing what would technically be called hallucinations. Not discrete objects, but my own private aurora borealis – amorphous floating blobs and faintly-colored shimmering, swirling auras. After about fifteen minutes of this phantom audiovisual show, I began to feel uncomfortable and headed back to join the others.

Moral: you can’t see nothing. You can’t hear nothing. Your brain won’t allow it.

It’s our senses’ job to let us know what’s going on out there. When absolutely nothing’s going on, they freak out and make things up. They tell us there’s something there when there isn’t.

That doesn’t mean that when there really is something there, they always file accurate reports about it. But that’s another story.