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December 29, 2010 3:31 AM   Subscribe

What exactly is happening in my brain that creates the very real feeling that I am covered in spiders when I am not, in fact, covered in spiders?

I have inherited a mild fear of spiders from my Mother.1 For a short time after thinking about, talking about, or seeing a spider or spiders, I experience sporadic and localised sensations of spiders on my arms, legs, neck - any exposed skin, really.2 I know these sensations to be false, but will almost always investigate them. On occasion, I will move to another area or shake off (much like a wet dog). This sensation occurs less frequently with other crawling insects. I am not afraid of most crawling insects. The sensation does not occur at all with wasps although I am terrified of wasps.3

I know that many others experience similar feelings when directing thought to insects, small reptiles, &c. I have always assumed that the feeling was universal, but I was talking about it with some people today and one of them had no idea what I was talking about. I have a friend who feels it most acutely when discussing snakes despite having never seen a snake in real life. Even cartoon snakes evoke frantic leg and arm rubbing, &c. I suspect such feelings offer some evolutionary advantage, and that's nice if you want to talk about that, but my real questions:
What exactly is happening in my brain that creates the very real feeling that I am covered in spiders when I am not, in fact, covered in spiders?4

How does it work?

Is this brain subroutine responsible for other imaginary sensations? If so, how can I use this subroutine to my advantage?

The sensation is usually bookended by a shiver and is not merely limited to areas of my body with hair, nor is it limited to parts of my body that I can't see. I do not find it debilitating or even annoying, so I don't need advice on overcoming my fears.

1 I don't mind spiders existing or hanging out in the same room as me, but the moment they get too close there's a rush of blood that switches my brain to autopilot and they meet the blunt end of the nearest thing I can grab.

2 It's that feeling you're feeling RIGHT NOW!

3 Fun stories about wasps:
One time in my early teens I was sitting at the bus stop and something landed on my collar. I brushed it off my collar into my shirt. It was a wasp. It responded to my act of perceived aggression with sustained stinging IN MY NAVEL. I panicked. I literally ripped my shirt open and squashed the fucker's head between my thumb and forefinger but the rest of the wasp KEPT STINGING, and now I had halved its length, it was more difficult to extract from my navel. At this point I was barely conscious, but apparently I ran away, leaving my wallet, cellphone, and schoolbag at the bus stop.

Another time a group of us were putting our shoes back on after kicking a ball around at lunchtime. About 50 metres away, the school caretaker was spraying a wasp nest with a hose. This resulted in their being lots of confused and angry wasps, and one confused and angry 15 year old (me), who received 22 stings to the rest of the group's 3.

Last year, in the middle of winter, some months since I last saw a wasp, I was sitting at the back of a crowded bus at about 7 in the morning. A wasp flew in through a window near the front of the bus, came straight down the aisle, stung me on the arm, and left though a window near the back.

Earlier this year, we were fishing from rocks and I was attacked by a little bastard wasp (my name for the little bastard wasps who eschew yellow stripes for assassin black and whose head, abdomen, and thorax seem to be completely independent entities). I flailed around a bit, lost a $60 lure down a crack, and ran away, breaking my ankle in the process.
4 One time I was covered in spiders. This is more traumatic to recount than the wasp attacks though I remain only mildly afraid of spiders. Is it relevant that I am verbose when discussing wasp attacks and unable to even articulate a summary of the time I was covered in spiders?
posted by doublehappy to Science & Nature (9 answers total) 7 users marked this as a favorite
This is fascinating! I hope you have a response from an informed expert on phobic reactions. From my very limited knowledge (A-Level Psychology!) it is a tik of the nervous system which has adopted false/overblown responses to the stimulus you are scared of via your screwed up brain! Because your response is irrational in proportion to the danger, your brain cannot distinguish between perceiving a spider that is in the room/in your mind and a spider that is on your body... At least that's what it feels like to me.

NB. I didn't read the entire textbook chapter on phobias because it had a huge picture of a spider. I also cannot bring myself to watch documentaries or read articles on phobias because they will inevitably involve images of the little nasties.

Plus the thing that is oh-so-freaky about them is a that 8 is a helluva lot of legs, which will tingle - hence, tingly feelings! Charlie Brooker calls them "mobile nightmare units".

Ugh, I'm so arachnophobic that I can't bear to type the word too much.

I'm gonna go now...
posted by dumdidumdum at 4:27 AM on December 29, 2010

One time I was covered in spiders. This is more traumatic to recount than the wasp attacks though I remain only mildly afraid of spiders.

The fact that the experience itself was traumatic might be key.

I have had numerous instances of being covered in various crawlies, including cockroaches, daddy longlegs, and wood ticks, but never experienced the sensation you speak of until I had to combat a bedbug infestation, which was a profoundly traumatic experience. Now I feel that crawly sensation, and I HAVE to make sure it's not a bedbug, even if there is no way it could possibly be one.

It had never occurred to me to be afraid of bedbugs, or really any bugs, before, but now those things give me the howling goddamn fantods.
posted by louche mustachio at 4:45 AM on December 29, 2010

True: this is called "formication" and it is a version of "delusional parasitosis," common especially among detoxing opiate addicts!
posted by spitbull at 4:48 AM on December 29, 2010 [2 favorites]

Here is a great website on delusional parasitosis hosted at UC Davis, with a lot of scientific information on the syndrome, which is quite common.
posted by spitbull at 4:50 AM on December 29, 2010 [1 favorite]

I would guess that you're having little skin sensations all the time, but when creepy-crawlies are on your mind, you're more likely to notice and react to those sensations. Other times, those skin sensations come and go without you even being conscious of them. This summer I had a lot of centipedes in my house (OH THE HUMANITY), and for about a month I was jumping at every tiny sign of movement out of the corner of my eyes. Now that it's winter, I'm back to my blissful obliviousness.
posted by overeducated_alligator at 5:01 AM on December 29, 2010 [1 favorite]

I think overeducated_alligator has it. When I have nothing better to pay attention to, I notice all kinds of itches and such. When something worthwhile is occupying my attention, those itches "disappear".

Have you correlated this at all with caffeine intake? When I'm overcaffeinated (like, driving from St. Louis to New Hampshire levels of overcaffeination), I swear I can feel my hair and fingernails growing. Same sort of sensation.
posted by notsnot at 5:13 AM on December 29, 2010

I lived in a trailer in the middle of a pine forest for a year. Pine straw is a really fine breeding place for really big cockroaches, and twice I woke up with a cockroach crawling on me. For years afterward I would wake up screaming, sure that there were roaches somewhere on my body. In fact, I just recently stopped.

It's a traumatic event - it's really no wonder you have this sensation.
posted by Evangeline at 5:51 AM on December 29, 2010

I often have a bit of delusional parasitosis after I've been traveling, because I am afraid of bedbugs, so I interpret all the ordinary skin sensations as OMG BEDBUGS CRAWLING ON ME. Then eventually I don't find any bedbugs, so I interpret the exact same skin sensations as "Meh, just skin sensations, no bedbugs here."

So my bet is that you can reprogram your cognitive centers to parse those feelings as "Meh, skin sensations" rather than OMG SPIDERS, but because this is a long-standing fear for you it will probably take some work.
posted by Sidhedevil at 12:56 PM on December 29, 2010

This story pertains to your third question.

And, based on your other questions and issues - good luck with reading it. (No spiders, but...)
posted by peagood at 8:57 PM on December 29, 2010

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