Comments on: Nature is stupidly clever

Nature is stupidly clever

orthogonality — Fri, 10 Jun 2005 07:18:54 -0800

"Creatures are out there that can control brains." [pdf]

The women "spent more money on clothes and were consistently rated as more attractive", but were "less trustworthy and had more relationships with men". The men become "less well groomed undesirable loners who were more willing to fight". All "are at greater risk of being involved in car accidents". Why? Something has its tentacles in their brains. They probably got it from that cuddly old species, the domestic cat, which the parasite infects by making infected rats "almost taunt" the cats into eating them.

Parasites in the brain alter their host's behavior. It's not just video game fiction. Various multi-host parasites make their living by making their hosts less ambulatory and less willing to explore, by castrating them and making them less cautious of predators, or by forcing their hosts to stay out all night so as to be eaten in the morning. These parasites offer yet another example of how stupidly clever evolution can be, and raise questions about how free "free will" really is.

By: orthogonality

orthogonality — Fri, 10 Jun 2005 07:27:49 -0800

This isn't a call-out of kenko's thread, but a defense: the implausibility of the hoax isn't that creatures exist that target and control other creatures' brains, only that they'd need something as grossly obvious as a grasping tentacles to do so. Blind evolution routinely exceeds the imagination of even intelligent (video game) designers.

By: jperkins

jperkins — Fri, 10 Jun 2005 07:38:12 -0800

That's the freakiest shit I've read in a long while....

By: dougny

dougny — Fri, 10 Jun 2005 07:44:58 -0800

So, parasites are eating my brain? That is some disturbing shit.

By: keswick

keswick — Fri, 10 Jun 2005 07:46:54 -0800

Midichlorians?

By: Pressed Rat

Pressed Rat — Fri, 10 Jun 2005 07:49:08 -0800

"Interestingly, for those who draw glib conclusions about national stereotypes, the number of people infected in France is much higher than in the UK. " Too funny by half.

By: brownpau

brownpau — Fri, 10 Jun 2005 07:51:00 -0800

Interesting stuff, thanks, orthogonality. I wash my hands thoroughly after cleaning out the litter box, but I've always been paranoid about toxoplasmosis ever since I heard about it, and I still wonder whether the creeping infection is laying hold on my brain. I think I already have the "loner" and "poor reaction time" symptoms. On preview: dougny, from what I'm reading, the brain-eating only happens when your immune system is compromised. Otherwise, I suppose there's an uneasy truce going on in cat owners' heads.

By: delmoi

delmoi — Fri, 10 Jun 2005 07:56:16 -0800

facinating. I wonder if there could be a theraputic (or malicious) use of these types of things and genetic engeneering. Imagine a tuned bug that can release anti-depressants only when it detects you're under stress. Or something that releases appitite suppressants untill Leptin and Insulin levels indicate you've lost enough weight. When you're done they'd have a 'kill' switch. Take a pill and remove it from your brain, if you'd like.

By: orthogonality

orthogonality — Fri, 10 Jun 2005 07:59:19 -0800

delmoi writes "Imagine a tuned bug that can release anti-depressants only when it detects you're under stress." Apparently, there's (mentioned in link five of the post) a parasite that releases opioids-- of all things --, into host hamsters; but I couldn't find a specific article or paper on that to link to.

By: mowglisambo

mowglisambo — Fri, 10 Jun 2005 08:04:54 -0800

If 50% of the American population is infected (and it's probably been like this for awhile), I sort of don't see what the big deal is. I mean it's an unpleasant thing to contemplate, but no less pleasant than the idea that my mind is controlled by neurotransmitters completely against my free will (*gasp*). Also, the study doesn't appear to pick apart cause and effect-- maybe people with those personality atributes aremore likely to get infected in the first place (being a loner and/or vamping yourself up doesn't seem to have a homologue in being less intimidated around predators. Not to mention the fact that there's no evidence humans are sensitive to cat pheromones-- as Sapolsky points out, part of what makes Toxoplasma so interesting is its specificity.) And I suppose its not worth mentioning, but saying that certain parasites "know" more about the brain is gratuitous at best. That's like saying electrons know more about physics than we do.

By: Doohickie

Doohickie — Fri, 10 Jun 2005 08:10:07 -0800

One startling fact to emerge from research is the great differences in levels of infection. In France and Germany, for example, about 80%-90% of people are infected — nearly twice that in Britain or America. Sorry, I ain't buyin'. They say this parasite makes men more likely to fight. If this is true, and the French & Germans have a much higher infection rate, why aren't their asses in Iraq?

By: Doohickie

Doohickie — Fri, 10 Jun 2005 08:10:30 -0800

*wondering if quonsar has a cat...*

By: brownpau

brownpau — Fri, 10 Jun 2005 08:11:17 -0800

"You see, their young enter through the ears and wrap themselves around the cerebral cortex. This has the effect of rendering the victim extremely susceptible to suggestion. Later as they grow follows madness... and death. These are pets, of course. Not quite... domesticated."

By: trondant

trondant — Fri, 10 Jun 2005 08:14:42 -0800

If 50% of the American population is infected 51%.

By: TimothyMason

TimothyMason — Fri, 10 Jun 2005 08:19:06 -0800

If this is true, and the French & Germans have a much higher infection rate, why aren't their asses in Iraq? Because the bug does not make you militaristic; it makes you an aggressive loner. Come over here and I'll show you. Me & my French cats.

By: caution live frogs

caution live frogs — Fri, 10 Jun 2005 08:22:23 -0800

delmoi wrote "Or something that releases appitite suppressants untill Leptin and Insulin levels indicate you've lost enough weight." Unfortunately humans don't respond to leptin. Rats do. Give a rat leptin, it stops eating. The people who found this thought they finally had the weight-loss magic bullet. Turns out it is the magic fat-reducing bullet - just not for people. Reading a leptin paper in 1999 did generate the question that has driven my PhD thesis ever since, though. So some good came out of it. (For me anyway.) And brownpau... KHAAAAAAAAN!!

By: Derive the Hamiltonian of...

Derive the Hamiltonian of... — Fri, 10 Jun 2005 08:23:55 -0800

It was a relief to read in the first article that cats are the only species that Toxoplasma gondii can reproduce in. Presumably, if you are infected, the parasites in your body will eventually die, and you can prevent reinfection by staying away from cats. I would agree with the researcher interviewed in the BBC article; it seems likely that the parasite also has subtle affects on humans (like the ones posited in the other articles) even when it isn't growing huge, destructive cysts in the brain due to a weak immune system. I don't see why Toxoplasma gondii wouldn't deploy the same method it uses to make infected rats easy cat meals on an infected human brain, and surely there would be some effect. A chemical/manipulation that removes a rat's instinctual fear of cat scent does what to humans? I've always disdained cats as pets in favor of large dogs on the grounds that I can identify with large dogs more and dogs are generally more social and interactive, and now I feel doubly vindicated.

By: Citizen Premier

Citizen Premier — Fri, 10 Jun 2005 08:29:48 -0800

Zombie snails are the coolest, although it's probably not as much of a challenge for a parasite to control a snail 'brain.' By the way, does Scientific American really want you scanning their articles and posting them online for free? I've wanted to share stuff from them before, but since I can't find them online I assume they don't want to share it.

By: terrapin

terrapin — Fri, 10 Jun 2005 08:30:09 -0800

I, for one, welcome our brain-controlling feline friends.

By: milovoo

milovoo — Fri, 10 Jun 2005 08:30:46 -0800

There is a Carl Zimmer book that covers this pretty well if you feel like reading more about it.

By: Derive the Hamiltonian of...

Derive the Hamiltonian of... — Fri, 10 Jun 2005 08:31:03 -0800

Oh wait, I was totally wrong. Toxoplasma only reproduces sexually in cats, but does reproduce asexually in just about anything else . So, once you have it, it might be there to stay. I forgot about the whole sexual vs. asexual reproduction deal.

By: Gimpson

Gimpson — Fri, 10 Jun 2005 08:33:35 -0800

There was a kind of cool segment on parasites featuring affecting behavior in this TAL from 2003. Carl Zimmer is the interviewee in the segment.

By: cmacleod

cmacleod — Fri, 10 Jun 2005 08:37:06 -0800

I wonder if that Amoeba I have been diagnosed as having in my intestine will cause me to lose my sanity. ... wait.

By: Armitage Shanks

Armitage Shanks — Fri, 10 Jun 2005 08:46:22 -0800

I've always disdained cats as pets in favor of large dogs on the grounds that I can identify with large dogs more and dogs are generally more social and interactive, and now I feel doubly vindicated. It's certainly fortunate that the gigantic turds they drop by the billions are disease-free. Anything dangerous carried in dogshit would wipe out every major city in about two days.

By: caddis

caddis — Fri, 10 Jun 2005 08:48:20 -0800

Excellent post from so many different angles.

By: goodnewsfortheinsane

goodnewsfortheinsane — Fri, 10 Jun 2005 08:52:56 -0800

Which episode, Gimpson? Your link takes me to TAL's front page.

By: Smart Dalek

Smart Dalek — Fri, 10 Jun 2005 08:53:55 -0800

By: languagehat

languagehat — Fri, 10 Jun 2005 08:56:25 -0800

This reminds me of one of the best (and darkest) science fiction stories of the '70s, James Tiptree, Jr.'s "A Momentary Taste of Being." Talk about "questions about how free 'free will' really is"...

By: mokey

mokey — Fri, 10 Jun 2005 09:00:35 -0800

This is shocking. Absolutely shocking.

By: Civil_Disobedient

Civil_Disobedient — Fri, 10 Jun 2005 09:07:06 -0800

So, once you have it, it might be there to stay From the article:

"Once you are infected you cannot get rid of this parasite and the numbers of them slowly grow over the years," she said.

That's, uh, bad news. but saying that certain parasites "know" more about the brain is gratuitous at best. That's like saying electrons know more about physics than we do. I'm more fascinated by the evolutionary effects--it's not that the parasites are "thinking" to themselves, "Gee, if this rat stays up all night, they'll be more tired and susceptible to being eaten by a cat in the morning." It's just that by process of natural selection, those parasites that adversely affect the social behavior of the rats are the ones that get eaten by cats, thus facilitating their reproduction. It's absolutely amazing, and thoroughly scary stuff. And trondant: Ha!

By: Faint of Butt

Faint of Butt — Fri, 10 Jun 2005 09:07:49 -0800

Excellent post, orthogonality. Fascinating topic and well-constructed. And the reference to the brain-eating video game mollusc thread was clever and topical, and not at all out of line. Well done.

By: BrotherCaine

BrotherCaine — Fri, 10 Jun 2005 09:30:26 -0800

I think it's episode 274 from 'This American Life'. Does this parasite harm cats at all, or is it actually helpful for them? oh and Brownpau, KHAAAAN!

By: Extopalopaketle

Extopalopaketle — Fri, 10 Jun 2005 09:37:32 -0800

The men become "less well groomed undesirable loners who were more willing to fight". All "are at greater risk of being involved in car accidents" Great. I am a motorcycle-riding, metrosexual, socialite male. With a cat. Let the transformations begin.

By: Derive the Hamiltonian of...

Derive the Hamiltonian of... — Fri, 10 Jun 2005 09:50:11 -0800

Civil_Disobedient: Thanks, I didn't read the second page of the Times article for some reason, or I would have caught that. This really is an excellent FPP in that the linked articles as a whole create a detailed overview of the topic, whereas any one of the articles alone has only part of the story. Armitage_Shanks: When I have the domicile and financial means to own a large dog, I will certainly pick up any monstrous turds it leaves around the neighborhood and my yard, or make my kids do it. Cleaning litter boxes is no picnic either, with or without the possibility of parasitic infection.

By: PhatLobley

PhatLobley — Fri, 10 Jun 2005 09:50:14 -0800

Great post. I'm scared out of my parasite-eaten mind.

By: Mr_Zero

Mr_Zero — Fri, 10 Jun 2005 09:57:18 -0800

Here is part of an article from Phoenix last year. This guy had a brain parasite that apparently blocked his "I shouldn't do that, it will be bad" response. I can not find the whole article but here is the first bit. The Maricopa County Medical Examiner's Office has ruled that last week's death of a top Phoenix official in a car accident was a suicide. City Finance Director Kevin Keogh died of "multiple traumatic injuries" suffered in the Dec. 8 accident, the office said. Scottsdale police have said that Keogh, 55, climbed out the window and onto the top of his moving car while it traveled down Camelback Road, then jumped from the hood. He was pronounced dead If I remember right he contracted the parasite while in Mexico. I believe he was a respected member of the city and and in charge of the light rail project.

By: jokeefe

jokeefe — Fri, 10 Jun 2005 10:02:46 -0800

Oh, WTF. So being deadly allergic to cats finally pays off. Good thing I never let one of the evil mind-controlling parasites in here. Or that there toxoplasmosis thingee either. *bah-dum* Here all week, etc.

By: jokeefe

jokeefe — Fri, 10 Jun 2005 10:12:20 -0800

Oh, and languagehat, a tangential shoutout once again to Tiptree; The Screwfly Solution remains the single most frightening story I have ever read (mileage will vary according to gender).

By: peacay

peacay — Fri, 10 Jun 2005 10:21:28 -0800

I'm not giving up pussy.

By: orthogonality

orthogonality — Fri, 10 Jun 2005 10:29:15 -0800

It's the baroque, apparently "unnecessary" complication of Dicrocoelium dendriticum's life-cycle that really gets me. Its life-cycle involves parasitizing first snails, then ants, then sheep, and so it's developed a way to disrupt the host ant's behavior such that the ant is more likely to be eaten by a sheep, by directly altering the brain. It's a life-cycle that makes little "sense" if animals are "intelligently designed" by a Creator, and that demonstrates the ability of evolution to find the oddest damned ways for creatures to "make a living", while at the same time demonstrating that an ant's behavior (and by extension our own) is a "merely" physical manifestation of a physical brain. The whole story is a triumph of materialism (in the sense of belief only in moving matter, not in the sense of wanting to acquire lots of wealth) over superstition and spirituality.

By: sonofsamiam

sonofsamiam — Fri, 10 Jun 2005 10:39:59 -0800

Memetic spread is the propagation of some replicable pattern of physical activity from host to host. These guys have more pattern-integrity, but apparently a weaker and less refined influence on the host. They seem largely substrate-dependent, but it's possible that we are just not used to looking at phenomena that possess integrity across different substrates. It would be cool if replicators could be found in other inter-human networks: maybe certain pheremonal patterns could trigger the release of similar patterns in the people around. Or the micromovements of eyelids and posture that we typically only catch unconsciously. Conjecture: in any sufficiently rich system of communication, "parasitic" replicators will spontaneously appear. On preview: sorry for all that, the worm in my brain needs to be placated with some more coffee. On preview 2: The whole story is a triumph of materialism [...] over superstition and spirituality. That seems like a huge jump. There's no metaphysic that could be compatible with this?! Not the one popular with US christians these days, but it's a big world.

By: freebird

freebird — Fri, 10 Jun 2005 10:45:02 -0800

Aside from the whole horrific-brain-eating-behavior-controlling-plague thing, which is certainly fascinating, I love the symbiosis. The cats carry a parasite which infects rats which makes them easier prey which spreads the parasite to other cats...that is totally cool. Great post. OP: I am totally on board with strict Darwinian "materialist" evolution. Having said that, if you're going to have an intelligent architect, it's clear from everything else that they'd need to have a sense of humor and enjoy baroque, rube-goldberg constructions. Why not this? Or - this could be the thing that got some sub-creator in trouble, like the giant pink tree that got the midgets fired in Time Bandits!

By: Asparagirl

Asparagirl — Fri, 10 Jun 2005 10:50:18 -0800

The women "spent more money on clothes and were consistently rated as more attractive", but were "less trustworthy and had more relationships with men". Eartha Kitt as Catwoman, anyone? Mrrrow!

By: caddis

caddis — Fri, 10 Jun 2005 10:51:14 -0800

By: ereshkigal45

ereshkigal45 — Fri, 10 Jun 2005 11:19:55 -0800

jokeefe: Thanks for posting about The Screwfly Solution. I had never read that. Absolutely chilling.

By: ori

ori — Fri, 10 Jun 2005 11:25:39 -0800

I really wish I hadn't read this. I'm never petting a cat again.

By: grapefruitmoon

grapefruitmoon — Fri, 10 Jun 2005 11:32:00 -0800

Fascinating post. I wonder if infection with the parasite has been linked to the high traffic of kitten war...

By: Civil_Disobedient

Civil_Disobedient — Fri, 10 Jun 2005 12:11:34 -0800

maybe certain pheremonal patterns could trigger the release of similar patterns in the people around. Or the micromovements of eyelids and posture that we typically only catch unconsciously. I think the implications of this are huge--are our brains so similarly wired to our lesser-mammalian friends that the method of infection and (consequentially) reproduction are the same? The parasite must feed off a particular area of the brain that is common in mammals and produces the same chemicals that bait these critters. The only way the parasite would be successful is if the social response pattern to infection was identical from host to host.

By: zoogleplex

zoogleplex — Fri, 10 Jun 2005 12:12:21 -0800

No wonder my brain doesn't work as well as it used to. I just thought I was getting old. And no wonder I respond like an automaton when my cats make the "I'm hungry" meow. Here's your Pounce, O Puissant Fuzzball Overlords...

By: davy

davy — Fri, 10 Jun 2005 12:18:54 -0800

I'm pretty sure I've had toxoplasmosis since at least my early teenhood. Do y'all think I might be symptomatic?

By: occhiblu

occhiblu — Fri, 10 Jun 2005 12:23:57 -0800

Not to spoil all the fun, but most toxoplasmosis infections come from undercooked meat or unwashed fruits and vegetables. Which hasn't stopped me from staring warily at my cat all morning, but still... Just avoiding cats doesn't eliminate your risk.

By: meehawl

meehawl — Fri, 10 Jun 2005 12:59:59 -0800

If 50% of the American population is infected (and it's probably been like this for awhile) The whole toxo thing has been around for a while, and the CDC has been tracking it for ages and it's nothing like ~50%. Mostly, it's a function of how rare people like their meat. The cat infection route is minor, but significant.

We found an overall T. gondii IgG antibody prevalence of 15.8% among persons 12–49 years of age in 1999–2000, indicating that approximately 1 in 6 persons in this age group was infected with T. gondii ... Predicting future trends in T. gondii prevalence in the United States is difficult because we do not have a national estimate of what proportion of T. gondii infections are attributable to undercooked meat exposure or to cat feces, soil, or water exposure. A large European case-control study that examined these factors showed that undercooked meat accounted for the largest portion of risk for T. gondii infection (30%–63%, depending on location).

The whole "slut theory" funding drive really kicked off with Flegr's 1999 classic of operationalised psychology, Changes in the personality profile of young women with latent toxoplasmosis. Personally, I was most impressed with The Sun's research on the cat connection a couple of years back...

Famous moggy owners include stunning Hollywood star Demi Moore, 40, who is having a passionate affair with Ashton Kutcher, 25, and pop babe Dannii Minogue, though there is no suggestion they have the bug.

By: meehawl

meehawl — Fri, 10 Jun 2005 13:01:24 -0800

Hey the first CDC link crapped out. This is it.

By: Specklet

Specklet — Fri, 10 Jun 2005 13:29:38 -0800

This is off the charts weird.

By: arse_hat

arse_hat — Fri, 10 Jun 2005 13:45:55 -0800

My cats are making me less appealing and more confrontational? FUCK YOU! *scratches arse*

By: jokeefe

jokeefe — Fri, 10 Jun 2005 14:02:19 -0800

Ah, ereshkigal45, I was going to say 'glad you liked it', but that hardly seems to fit. The Screwfly Solution remains the only piece of literature I can think of where the gender of the author absolutely changes its effect-- what I mean by that: the first time I read the story (and once I recovered a bit and stopped shuddering) I immediately flipped to the anthology's table of contents, Who the hell wrote that? only to be confronted with the name James Tiptree Jr. I didn't know at the time that of course this was the pseudonym of Alice Sheldon... I was terribly dismayed to think that this story was written by a man. It makes a huge difference, yes? Written by a man, it's a vicious misogynist fantasy; by a woman, an articulation of our deepest and oldest fears.

By: caddis

caddis — Fri, 10 Jun 2005 14:50:49 -0800

Candy is dandy, but liquor is quicker [Ogden Nash] yet cats are forever.

By: gsb

gsb — Fri, 10 Jun 2005 14:51:30 -0800

Nice post. I like the way this narrative has worked, the kinda scary cat toxic parasite creepyness. Now go watch this.

By: melissa may

melissa may — Fri, 10 Jun 2005 16:34:31 -0800

Why do I feel like orthogonality just called me a ho? Well, I don't care -- it's still a great post. Now do one on lytico-bodig and make my life complete. In the meanwhile, I'm off to kiss my cats, and a few sailors if I can find some.

By: caddis

caddis — Fri, 10 Jun 2005 17:46:53 -0800

Well, now that we have gotten towards the end of the comments, I have to say that this is the best post I have seen so far this year! It creatively responds to kenko's post, it is very interesting in its own right, the intelligent design dig was great, its overall creativity is off the scale, and there were several more levels to its subtlety. This post should be put into a wiki on how to make a great mefi post.

By: zardoz

zardoz — Fri, 10 Jun 2005 17:49:35 -0800

This reminds me of Greg Bear's Vitals, a strange and very unsettling "techno-thriller".

By: joelf

joelf — Fri, 10 Jun 2005 18:27:24 -0800

WE MUST TRAVEL TO THE BRAIN SLUG PLANET AND WALK AROUND WITHOUT HATS.

By: orthogonality

orthogonality — Fri, 10 Jun 2005 18:33:34 -0800

caddis writes "I have to say that this is the best post I have seen so far this year!" Thanks!

By: Gyan

Gyan — Fri, 10 Jun 2005 19:26:28 -0800

Isn't this some sort of normative posturing? Does the brain as an organism really "know" that toxoplasma gondii is not "supposed to be there"? Serotonin, dopamine, anadamide, toxoplasma are all molecules. Heck, if nothing is done about this, maybe in a few million years, TG may become the latest inculcated neurotransmitter.

By: Vulpyne

Vulpyne — Fri, 10 Jun 2005 19:45:18 -0800

jokeefe: "I was terribly dismayed to think that this story was written by a man. It makes a huge difference, yes? Written by a man, it's a vicious misogynist fantasy; by a woman, an articulation of our deepest and oldest fears." I'm not sure why you think the gender makes a difference. It didn't seem like the tone of the story was hostile to women. Being turned into a monster that is forced to kill the ones you love seems fairly far from a "misogynist fantasy" to me. (I know that I'd choose death first.) Anyway, I think you may have been reading too much into the story. It's just a creepy fiction. In conclusion, thanks for posting the story. I enjoyed reading it.

By: blahblahblah

blahblahblah — Fri, 10 Jun 2005 20:01:17 -0800

Hey wait -- there's good news! From meehawl's link: "The subjects with latent toxoplasmosis had higher intelligence, lower guilt proneness, and possibly also higher ergic tension." So infected women become brilliant, slutty, and want back rubs. Sounds like a Robert Heinlein novel.

By: wobh

wobh — Fri, 10 Jun 2005 20:36:54 -0800

Is there another parasite that causes "cat lady" syndrome?

By: OmieWise

OmieWise — Fri, 10 Jun 2005 20:58:58 -0800

Very nice post, orthogonality. I've known about some of this for some years, as E. Fuller Torrey has been a big proponent of linking schizophrenia to toxoplasmosis and cat-ownership. I happen to think Torrey is an ass and a stooge for pharmaceutical companies, and that almost all the research on the biological origins of schizophrenia is sloppy, self-serving and inconclusive (or disconfirming). And the toxo links are all really about the same research (his research, and his guy in Geneva), so are unconvincing in that regard. Put into context of the other links about parasitology, however, they paint a chilling picture that does make for an excellent post. And despite my scepticism about evolutionary psychology, I'm not petting a cat anytime soon. Thanks.

By: arse_hat

arse_hat — Fri, 10 Jun 2005 21:09:01 -0800

" linking schizophrenia to toxoplasmosis and cat-ownership" I think that may be right but the tiny little Oompa Band on my windowsill is telling me otherwise.

By: dhruva

dhruva — Fri, 10 Jun 2005 21:49:16 -0800

Great post! and trondant, that made me laugh out loud.

By: heavy water

heavy water — Fri, 10 Jun 2005 22:03:07 -0800

There's one huge caveat to this line of research that should nip most people's paranoia in the bud: effect size. There's a reason the sample sizes needed to detect this effect are in the hundreds. The effect is very small. Headlines screaming that the human race is about to suffer devastation at the hands of a brain-eating parasite make for a good story, but the reality is that we're talking about changes of fractions of a point on personality scales that might have means of, say, 20 or 30. The reason there isn't a huge toxoplasma-associated characterological difference between French and Americans in the traits discussed by the researchers (e.g., sociability, aggression, etc.) is that the disease is a minor blip in the grand scheme of things. The concept of effect size is, unfortunately, almost always overlooked by both science journalists and media consumers. Saying that there's a significant effect tells you nothing about how big the effect is. By way of analogy, it's been shown that students with last names beginning with letters earlier in the alphabet (e.g., A, B, or C) perform (highly) significantly better on the SAT than students later in the alphabet. Reason to change your kids' last names? No, because the size of the effect is tiny: about a point or so. No reason at all to panic. Bottom line: pretend the toxoplasma results had been reported in headlines reading "feline disease changes extraversion scores by one or two percent" and you'll feel much more comfortable.

By: orthogonality

orthogonality — Fri, 10 Jun 2005 22:03:46 -0800

Gyan writes "Isn't this some sort of normative posturing? Does the brain as an organism really 'know' that toxoplasma gondii is not 'supposed to be there'?" This is where Richard Dawkins's stance of taking a "gene's eye view" is useful. (My paraphrase, Dawkins would phrase it more elegantly.) T. gondii's genes are replicated only if T. gondii is successful. Therefore, T. gondii's genes make T. gondii do things that cause the production of more T. gondii (and thus T. gondii genes). T. gondii and its genes are working for its genes' benefit, not its host's benefit. Similar, your brain (or a cat's brain) is, ultimately, made up of human (or cat) genes, genes that have had millions of years to "learn" to do things, and work in concert, for their benefit. Evolution pretty much requires that any organism be as good as possible (within a network of possibly conflicting constraints) at producing more of its genes. Why? Because the organism competes against others of its own species -- any organism that is even a little less precise will leave fewer copies of its genome. So every organism is a highly calibrated machine, a machine for producing more of the genes that make up the organism. Like any highly complicated machine made up of many many tiny subsystems (think of far less complicated machines, like cars or computers or hi-fidelity stereo systems, none anywhere near as complicated as the simplest one-celled organism), that calibration must be very precise. Think of tuning a car, or adjusting a hi-fi stereo: even minor deviations from calibration can produce substantial performance problems. Therefore, anything that makes the organism do things contrary to what its genes "want" it to do -- for example T. gondii -- is in all likelihood going to make the organism perform worse, not better. This is simply an expression of a simple idea, that there are far more ways to be wrong than right, that out a universe of possible configurations, only a very few combinations will work in any particular environment. Imagine a Beethoven symphony: even though there can be many different interpretations of a particular symphony, each note must be correctly played by the designated instrument -- there are far more ways of producing something that is not that symphony than there are of producing that symphony, let alone producing it masterfully and in high fidelity. So, no, it's not normative posturing: T. gondii is monkey-wrench thrown into a precisely machined jet engine. designed to disrupt it -- and indeed, it acts to get rats eaten so it can complete its life cycle. (That said, there are examples of commensal life forms, and rare but vitally important cases where mutualism has become a cornerstone of life: chloroplasts, the part of plants that turn sun light into food, and mitochondria, the part of animals that turn oxygen into energy, are both thought to have originally been separate life forms, that probably began mutualism after being parasites or more likely prey. Now mitochondria are so ingrained in us (literally, with hundreds in each cell) that while they maintain separate DNA, important sections of their DNA, vital to their functioning, are now contained not in them, but in our own nuclear DNA.)

By: Gyan

Gyan — Fri, 10 Jun 2005 22:42:02 -0800

orthogonality : "T. gondii's genes make T. gondii do things that cause the production of more T. gondii (and thus T. gondii genes). T. gondii and its genes are working for its genes' benefit, not its host's benefit." Evolution is not teleological, including, with respect to survival. Evolution is a tautological retrospective narrative that frames the multi-dimensional cascade of events in terms of intentional devices, but that's only to sound comforting to us. The underlying driver of change is (putatively) mathematically-rigid non-intentional laws, not instincts and goals. any organism that is even a little less precise will leave fewer copies of its genome. Many mutations aren't even harmful, just non-significant. There's no particular pressure to weed them out, either. even minor deviations from calibration can produce substantial performance problems. There's shock-absorption and workarounds as well. This is simply an expression of a simple idea, that there are far more ways to be wrong than right, that out a universe of possible configurations, only a very few combinations will work in any particular environment. There's no clear answer as to what constitutes life or consciousness, so arguing that things must progress as they have been, assumes favoring a certain framework. We just don't have the evolutionaryily long-term experience to falsify such notions, even if our intuitions indicate otherwise.

By: hojoki

hojoki — Sat, 11 Jun 2005 02:48:28 -0800

This is extremely interesting and disturbing stuff. It makes me wonder about ancient Egypt's fascination with felines and if that civilization both rose to greatness and crumbled because of their kitties. Glad I'm allergic.

By: Tarrama

Tarrama — Sat, 11 Jun 2005 05:05:23 -0800

CATS: You have no chance to survive make your time. Ha Ha Ha Ha ....

By: lia

lia — Sat, 11 Jun 2005 07:19:37 -0800

74 comments on a thread about parasites affecting behavior and no one's mentioned the Star Trek: TNG episode Conspiracy? Where have all the old MeFi nerds gone?

By: davy

davy — Sat, 11 Jun 2005 09:29:52 -0800

Being turned into a monster that is forced to kill the ones you love Would it be so bad if they deserved it?

By: OmieWise

OmieWise — Sat, 11 Jun 2005 11:22:34 -0800

heavy water writes "There's one huge caveat to this line of research that should nip most people's paranoia in the bud: effect size." hw-thanks for the words of sense about this. Just to clarify a bit about what I wrote before-Torrey, who runs the institute this research comes out of, has been jonesing for years to determine a biological cause for schizophrenia, and has changed his explanation of that cause as each set of data has proved inconclusive. He needs things like effect size to help him in his quest. I'm not suggesting that a life spent researching the biology of mental illness is in any way a bad idea, but Torrey's brand of research has always struck me as more of an obsession backed by pharma cash. His association with the pharmaceutical trade group cum "consumer's organization" NAMI has never endeared him to me either.

By: troutfishing

troutfishing — Sun, 12 Jun 2005 14:58:45 -0800

I'm not antisocial. Get away from me, all of you. Or you'll get a knuckle sandwich.

By: purephase

purephase — Sun, 12 Jun 2005 20:33:57 -0800

Too bad there wasn't more information on indoor cat infections. The following (from Fox no less): Outdoor cats that interact with other animals are particularly susceptible to the infection, but can, like humans, be checked for it and treated with medications if necessary... Seems to indicate that indoor cats are less-susceptible and that (the study) points to rats at the prime-carrier. I have never found a dead rat, my cat is an extreme indoor cat (she's terrified of the open door) so maybe (and here's wishful thinking) I am alright. I still bathe, so here's to hoping! ;)

By: milovoo

milovoo — Wed, 15 Jun 2005 09:29:22 -0800

In the "see also" for interesting parasite-caused behavior, it's worth checking out the snail parasite [Leucochloridium paradoxum] that causes the snail to develop a large pulsating bird-attracting tentacle to distribute it's eggs. Another interesting parasite is the crustacean Sacculina that infects crabs and causes the males to engage in false birthing behavior to distribute it's eggs. IIRC, this creature is also notable for retaining the smallest amount of original tissue during it's molting / infesting phase. I would be willing to bet that there are many more subtle parasite-influenced behaviors out there that we have not discovered yet.