Creeping On Little Cat Feet . . .

by wjw on March 19, 2012

Okay, kinda scared now . . .

Turns out that cats can alter our brains.   I mean literally restructure them. I mean, change our freaking behavior.

Well, not cats actually.  A parasite that lives in cats, Toxoplasma gondii.

It’s long been known that Toxoplasma can physically alter the brains of rats, to make them sexually attracted to the smell of cat urine.  It also eliminated the fear response, which means they lose their fear of predators.  This makes them want to hang around cats, who of course eat them, thus eating the parasite.  When the cat excretes the eggs of the parasite, rats or other animals may eat the feces, and start the cycle all over again.  Yum.

Somewhere between 10 and 20 percent of North Americans are infected with Toxoplasma.  And 40 percent or more of Europeans (who eat more raw meat and are thus more likely to be exposed to the parasite). In the developing world, it’s more like 90% in some places.


It’s long been assumed that Toxo doesn’t affect humans, because we’re not a part of its life cycle.  Turns out we were wrong.

Czech scientist Jaroslav Flegl has been studying Toxo for over twenty years, though his lack of English skills and his position at underfunded Charles University in Prague has resulted in his works not being known in the West till fairly recently.  Now his findings are being confirmed by researchers elsewhere.


Here’s what Toxo will do to you.

It will make you less afraid of, say, walking in front of cars, or being caught in a firefight.  (A couple of Turkish studies suggest that Toxo may be responsible for thousands of car accidents each year.)

Toxo will slow your reaction time.  (It really wants that big, furry predator to get you.)

Compared with uninfected people of the same sex, infected men were more likely to wear rumpled old clothes; infected women tended to be more meticulously attired, many showing up for the study in expensive, designer-brand clothing. Infected men tended to have fewer friends, while infected women tended to have more. And when it came to downing the mystery fluid, reports Flegr, “the infected males were much more hesitant than uninfected men. They wanted to know why they had to do it. Would it harm them?” In contrast, the infected women were the most trusting of all subjects. “They just did what they were told,” he says.

Why men and women reacted so differently to the parasite still mystified him. After consulting the psychological literature, he started to suspect that heightened anxiety might be the common denominator underlying their responses. When under emotional strain, he read, women seek solace through social bonding and nurturing. In the lingo of psychologists, they’re inclined to “tend and befriend.” Anxious men, on the other hand, typically respond by withdrawing and becoming hostile or antisocial. Perhaps he was looking at flip sides of the same coin.

Toxo can give you a form of schizophrenia where your brain literally shrinks.  (Nearly all tested schizophrenics with brain shrinkage were infected with Toxo.) (And it turns out that schizophrenia was an extremely rare disease until people began living with cats in their homes.)

It may increase testosterone production in human males, which may make them more attractive to women, which may result in the parasite being transmitted sexually.  (It’s not known whether Toxo can be transmitted sexually between humans, though it can by animals.)

I don’t know if there’s been a study done on crazy cat ladies yet, but it wouldn’t surprise me if . . . well, you can finish that sentence, I’m sure.

(It’s eating our brains!!!  Our brains!!!)

Is there a cure?  Why no, of course not.  Once your brain gets eaten, it stays eaten.

Once your behavior is changed, it will stay changed.

No free will with Toxo.  Assuming of course that you can have free will without it.


I’m going to go hide in the closet now.  But I know that my cat will be just outside, waiting for me when I come out.

Pat Mathews March 19, 2012 at 11:33 am

Crazy cat LADIES? After the description (also given in a humorous Analog short story many, many months ago) of how it makes you guys more geek and us women more sleek?

And doesn’t it really sound like Fandom there?

Pat, willing to let those furry predators catch me and make me love them, if they’d only wait for their breakfast until, say, after 6am!

Stacy March 19, 2012 at 12:37 pm

So that’s how Bitsy will finally be free of those pesky Asimovian protocols? I never completely trusted that cat avatar.

Lektu March 19, 2012 at 12:54 pm

“(And it turns out that schizophrenia was an extremely rare disease until people began living with cats in their homes.)”

Do we really have studies about the incidence of schizophrenia 7,000 years ago? Or, for that matter, reliable studies about incidence of schizophrenia just 200 or 300 years ago?

Rebecc March 19, 2012 at 1:58 pm

Yeah, this one is pretty damn freaky. On the other hand… Holy Whoa, Story Ideas.

DensityDuck March 19, 2012 at 5:42 pm

Yes; remember how they created an actual objective definition for “autistic disorder” and suddenly there was an “autism epidemic”

wjw March 19, 2012 at 11:32 pm

Pat, Crazy Cat Lady is a reference to the Simpsons. Sorry if that didn’t come across.

There is even a Crazy Cat Lady Action Figure:

Lektu, we do have a medical literature stretching back 4000 years to ancient Egypt. All the physicians tended to use the same texts, so there were a lot of copies.

How well they described schizophrenia, I don’t know. But the article sez that the incidence of schizophrenia went up in the mid 18th century, and that was when city folks invited cats into their homes.

Sean Craven March 20, 2012 at 1:49 am

This messed with me a bit, because I can think of particular people I know… Dude. Let’s place this in the proper perspective.

This is the first one we’ve been informed of.

Tori March 20, 2012 at 3:20 am

This parasite was a topic in my Biology of Infectious Organisms course. It’s also the parasite that’s the reason pregnant women shouldn’t clean catboxes, and it’s infecting otters on the west coast as well from city water run-off. Technically it gets taken up by bivalve filter feeders and then the otters eat the shellfish and become infected. No bueno! The parasitologists I work with/for study some crazy behavior-modifying organisms. If for whatever reason you want to research parasites, I can introduce you to some very knowledgeable specialists. They would be thrilled to meet with a researching author as opposed to the usual “delusional parasitosis” crowd that hunts them down. -.-;

wjw March 20, 2012 at 4:59 am


Wait, I can stop panicking. I don’t hang out with sea otters much.

Thanks for the offer, Tori. If I decide to do a story about parasites, I’ll know who to call. Though I’d have a hard time topping MLN Hanover’s series, where parasites really go to town on people.

Ralf The Dog. March 20, 2012 at 5:23 am

It sounds a little bit like Nodding Syndrome on turbo.

(Would be a good excuse for an FMRI study to find what parts of the brain are effected, followed by, a postmortem examination of the brain after the next fatality.)

Re: MLN Hanover’s series, I will check it out, when my reading list gets a bit smaller. If I remember, Robert A. Heinlein also did one that was later turned into porn, “Invasion of the booby snatchers.”

David W. Goldman March 20, 2012 at 6:16 am

I shall not resist referring you all to my 2008 Analog story, “Invasion of the Pattern Snatchers”:

Ralf The Dog. March 21, 2012 at 1:41 am

David, cool story.

Lektu March 22, 2012 at 12:59 am

Yes, I know about egyptian medical papyri. I wouldn’t be surprised to find medical texts among the copious sumerian “literature” (so to speak), which is older still. But descriptions of maladies in ancient texts are so vague that in many cases it is very hard to relate them to modern ones. When the Bible and other ancient texts talk about leprosy, in many cases they are not refering to M. leprae, but just about any disfiguring skin disease; descriptions of the bubonic plague’s symptoms do not exactly match modern Y. pestis outbreaks (though the relation between the old and new strands was recently proved, ISTR), and as recently as the 15th and 16th centuries, the “sweating sickness” hit England hard (and, to a lesser extent, also continental Europe), and we are far from knowing what caused it.
And that’s *physical* diseases. Let’s not enter the realm of mental diseases. I wouldn’t trust any attribution of schizophrenia older that the late 19th.
But, anyway, what I find surprising is that fact you quote about city people not allowing the cats into their houses until the mid 18th century. Could you please point to a source for this datum? (I’m really curious about it.)

Lektu March 22, 2012 at 1:10 am

OK, sorry. I see that it is a quote of the Atlantic piece: “In fact, he says, schizophrenia did not rise in prevalence until the latter half of the 18th century, when for the first time people in Paris and London started keeping cats as pets.”
Dogs have been considered something more than just domesticated beasts for at least 14,000 years (there’s these Natufian burials of humans and dogs together) and more likely 30,000+ years (shared human-dog burials 32,000 years old were reported just last year). Cats were domesticated more recently, but at least 9,500 years ago. It is very hard to believe that they were universally considered as non-pets for 90% of that time.

Pat Mathews March 22, 2012 at 4:02 am

In that case, ancient Egypt must have been riddled with it! And quite soon, cats spread into the Roman Empire, where they were quite useful for pest control. Were Roman streets ever swept? Even the alleys of the Subura? Hmmmm… was schizophrenia known in either culture? Some of the Roman emperors seem to have been barking mad in one way or another.

Lektu March 22, 2012 at 12:14 pm

Pat, that’s exactly my point: surely there were schizophrenic people in Egypt and the Roman Empire. But we cannot establish any reliable statistics, because contemporary descriptions lump together anything that seems like madness (from simple eccentricity to schizophrenia to any one of several physical diseases with mental symptoms). We have a bunch of competing theories about the cause of Napoleon’s death, and that was less than 200 years ago and his remains are preserved and have been studied. Prognosis of ancient people’s mental diseases seems like voodoo to me.

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