August 1, 2008

A mysterious phenomenon.

The air conditioner in my office is horribly loud, but I only notice when it cycles off. It goes off and I realize that I couldn't stand it. But if I couldn't stand it, why didn't I notice when it was on? And I also have the feeling that time reverses a bit: I seem to start hearing the noise a split second before it goes off. And I don't mean just once. I mean every time, thousands of times. I become aware of the noise and then it goes off. That's an illusion, of course, but I've experienced it so often that I know it's a very specific phenomenon, and I wonder how many other things there are that we perceive out of order like that.

21 comments:

Roman said...

Sounds a lot like the neural processes that trigger deja vu. The noise doesn't register until it's stopped, which stimulates the brain, making you conscious of the noise only after it has stopped. Kinda cool.
Strangely, once I read that, my A/C started bugging the crap out of me.

Simon said...

I believe there's a whole chapter in Scott Adams' book The Dilbert Future that talks about things like that.

blake said...

I have that with a refrigerator.

You tune it out, because it's necessary and you can't function if you're focused on it.

It's like being hit in the head with a hammer constantly: It feels so good when it stops.

calrablat said...

I've heard that deja vu happens when one half of the brain processes something sooner than the other half, so I imagine it could be the same phenomenon. For example, the right half of your brain registers that the AC just went off while the left half is still hearing it.

Revenant said...

It isn't necessarily an illusion. With most air conditioners, the compressor shuts off a little while before the fan does. This helps prevent condensation and mold, if I recall correctly. So it could be that the sound of that, or the change in the sound from the AC, calls your attention to it shortly before the fan shuts off.

raptros-v76 said...

Noises like air conditioners drove me to wear headphones when sitting around. They do help.

Eric Muller said...

I had this weird feeling you were going to post this.

EnigmatiCore said...

Shrooms magnify this effect.

Roy Lofquist said...

I live in Florida. I just leave the air conditioner off. I don't have many friends and I go through a lot of towels but at least it's quiet.

rhhardin said...

I notice the same thing when the crickets stop chirping.

Ann Althouse said...

Roman, great point. I wonder if there is research on this. It's such a distinct and weird thing. I know I'm not imagining the perception.

Calrabat, very interesting! Why would the brain be so defective?

Revenant: I like to explore this alternative, but why would I notice the signal and suddenly become annoyed by what I was otherwise ignoring? It's only the sudden silence that makes me retrospectively annoyed. Even if I could hear some click, there's no reason why it would make me feel annoyed by the noise. Well, maybe there's an idea like: Oh, good, the noise is about to end. I would have had to have -- without realizing it -- learned that the click precedes the end of the noise. Or I guess you're saying that there is a reduction in noise that is significant and then the complete cessation.

Daryl said...

And I also have the feeling that time reverses a bit: I seem to start hearing the noise a split second before it goes off.

That's because different parts of your mind are arriving at conclusions at different times.

You recognize that there has been a change in sound faster than you recognize what the particular change is.

But the human mind just isn't built to take into account in-brain delays. The world is complicated enough just trying to understand what's going on outside our brain.

It is a fallacy that the sensory input we experience is being generated in the world around us in the exact same instant as we experience it. But it is a comforting fallacy--it makes life easier.

amba said...

If I'm across the room from my laptop and the screen suddenly dims to save energy, I notice the event out of the corner of my eye as a bright flash of light.

I don't know why that feels related, but it does.

Revenant said...

Revenant: I like to explore this alternative, but why would I notice the signal and suddenly become annoyed by what I was otherwise ignoring?

The brain starts to ignore any pattern of sensory input it receives -- it starts being treated as "background", basically. For example, I have a ceiling fan that makes an annoying buzzing noise on its lowest setting. After a while I stop noticing it, but if something draws my attention to it I start being annoyed by it again because now my brain is consciously assessing it again. My guess is that the slight change in sound draws your attention to the annoying noise, causing you to be annoyed all over again. Before that the noise was constant, and your brain had been ignoring it.

The deja vu idea could explain it too, though, especially if you were situated so that the sound of the AC shutting off reached one ear before the other (e.g. if the sound was to the right or left). The ears communicate to separate hemispheres of the brain, and time lag between hemispheres is thought to be the reason for that "deja vu" feeling.

Or you could be imagining it. :)

rhhardin said...

I don't have an A/C myself, just (for the incredibly humid and hot days) a fexible duct I run up the basement stairs and point at my computer chair, which not only prevents mildew in the basement but cools me pleasantly down.

Sometimes the dog will park in front of it too.

Trooper York said...

I think it was internet explorer that did it.

Corky Boyd said...

This isn't your mind playing tricks. Had the same thing happen with one of mine. When it shut down it sounded like a "Jake Brake" of a diesel truck. Very unpleasant!

The compressor is about to fail.

Biff said...

I worked in an office with very loud air conditioning and a lot of humming electronic gadgets. I found that noise canceling headphones made a big difference in my mood and my ability to concentrate for long periods of time.

Anyway, the reaction to an absence of noise reminds me of when I was a kid, and my dad would be in front of the television, snoring loudly enough to be heard around the neighborhood, but if someone would turn off the tv, he'd jolt awake and say, "Hey! I was watching that!" As some of the other commenters suggest, a lot of the brain's activity is geared towards measuring changes, rather than constants. (Did something just move in the tall grass?)

I remember some experiments in undergraduate neuroscience lab, where it was possible to measure brain activity in critters like grasshoppers and flies. If you moved an object in their visual fields, their brain activity would skyrocket during even the slightest movement, but it would drop to baseline almost as soon as the object was stationary.

Amba's comment suggests a phenomenon similar to that experienced when you pass your arm under a stream of very hot or very cold water. The brain's initial interpretation of whether the water is hot or cold is often ambiguous or even incorrect. The important thing is the immediate, reflexive response to remove the arm from an area of potentially dangerous temperature change. There'll be time later to figure out whether it's hot or cold!

James said...

Mr Slothrop had a similar experience with rockets.

Synova said...

I think that dreams do that too.

Like when I was napping once and a "bang" woke me up and I remembered dreaming of blowing up a balloon bigger and bigger and then it popped.

Obviously I couldn't have been dreaming anything that would lead to needing a "bang" at the end of it.

But my brain still put the "bang" into some context even if it was after the fact.

woccam said...

Benjamin Libet in 1979 "made the hypothesis of a mechanism of referral of conscious awareness of
sensory stimuli backwards in time, and obtained experimental results that he considered
supportive of this hypothesis." This remains controversial.