"Our results suggest [...] these results lay the foundation for future research"
Its the classic do an easy little study, and suggest that the potential for results might point to further studies. Now you have something to tell your research coordinator next time they get in your hair.
Note that the 35,178 in this comment is actually a list, aka in python: [35, 178], and not the number 35,178 -- which would of course be a large enough sample size to make some observations.
The statistics in this paper are... not robust IMHO.
They do so many comparisons between the groups and never mention any multiple comparisons correction.
Interesting idea, I am not convinced right now - but let's see if it reproduces.
I believe it's spelled Goa'uld :) Who knows, but the very fact that a parasite can co-opt our sense of smell to make cat urine smell not as bad, is saying something.
I also assume that’s what mrfusion meant, but there is also Sabine Baring-Gould who wrote (among other works) “The Book of Were-Wolves”, which is clearly relevant to the topic of mysterious healing powers:
"we found that infected men had lower facial fluctuating asymmetry whereas infected women had lower body mass, lower body mass index, a tendency for lower facial fluctuating asymmetry, higher self-perceived attractiveness, and a higher number of sexual partners than non-infected ones. Then, we found that infected men and women were rated as more attractive and healthier than non-infected ones."
From a quick skim, it looks like they don't present anything which would distinguish which way the causal arrow points. Do the parasites make their hosts more attractive so they are more likely to be passed on, or do more attractive people have more sex that gives them opportunities to be infected?
Seriously, has the bar sunk this low? I was certain the authors would express caution in interpreting causality, but alas: "Our results suggest that some sexually transmitted parasites, such as T. gondii, may produce changes in the appearance and behavior of the human host".
Perhaps it's because I don't frequent the literature, but I interpret that as "T Gondii. may [provided by our level of statistical certainty in MANCOVA] produce changes". Otherwise, what's the point of performing a statistical analysis? Moreover what's the value of any assertion if it can be guarded by an unbounded-uncertainty keyword "may".
I think that's a classic case of reading between the lines and making implications where one shouldn't. If I'm using words that state uncertainty, it is because I am not certain, but only say it is a possibility. A research result that shows there is a correlation is already interesting without establishing or confirming causation. Their wording is exactly saying that. Without that paper we wouldn't even know there is a correlation!
How else would you like them to state that without being overly verbose?
> How else would you like them to state that without being overly verbose?
"Our results suggest that some sexually transmitted parasites, such as T. gondii, may be correlated with appearance and behavior of the human host."
I appreciate your viewpoint. I would counter it by saying that there are two sources of uncertainty here: choice of model & sampling variance. It's my opinion that in scientific writing, one should be precise with which source of uncertainty they are guarding. If I'm allowed to group these together, why can't I make a similar statement of causation of any old spurious correlation - when obviously my model is bad?
Considering this example again - isn't it arbitrary that the authors get to choose which hypothesis (among many, like attractive people being predisposed to own cats) they get to claim "may" be demonstrated?
> "Our results suggest that some sexually transmitted parasites, such as T. gondii, may be correlated with appearance and behavior of the human host."
But that is a different statement. They say that they found correlation and there may be causation. You say there may be correlation, a much weaker claim.
> Considering this example again - isn't it arbitrary that the authors get to choose which hypothesis (among many, like attractive people being predisposed to own cats) they get to claim "may" be demonstrated?
Of course it is arbitrary. But that was their hypothesis and you have to start with some hypothesis, no? They gathered data to establish correlation between the infection and attractiveness. They didn't gather data for anything else, so I think it's pretty reasonable to say we found correlation and further research might be interesting to see if there is causation.
Literally the next sentence says "Taken together, these results lay the foundation for future research".
If you go beyond the abstract and into the actual article, they are pretty careful to just list possibilities for the observed correlation. They certainly could have stated that it might just be spurious correlation there, but I don't blame them too much. These articles are supposed to be concise and not verbose and especially the abstract is supposed to be as concise and short as possible.
I agree with your general premise and the linked article though. It should be a given to consider that and ideally also state it in the article.
I was directly quoting the article and am not a domain expert. It is interesting to see some commenters here state that it isn't an STD. It appears this is an open question.
> Do the parasites make their hosts more attractive so they are more likely to be passed on, or do more attractive people have more sex that gives them opportunities to be infected?
T. Gondii reproduces in felines, and is transmitted initially through their feces to other hosts. Humans catch it most often through infected food (meat, vegetables) or liquids (water, milk). Humans cannot transmit T. Gondii to other humans, unless pregnancies, organ transplants or cannibalism are involved.
So, regardless of how attractive an host is, he won't have more or less opportunities to be infected with T. Gondii than anyone else. This is not a STD.
Unless there is some sort of correlation between attractiveness and eating poorly corked meat.
How about correlation between attractiveness and owning cats? Attractiveness and having a larger number of partners, which increases odds of exposure to cats / T. Gondii? These hypotheses seem plausible enough that I believe the authors are wrong in claiming causality.
Unless people are hooking up in barns I don't think frequenting partners that own cats would be correlated. House cats generally eat kibble, not infected mice.
Even then you'd have to infect yourself with the cat while getting together, as humans don't transfer to each other.
Personally I don't think there's any causation here at all with attractiveness directly.
It may be correlated with more outdoorsy people, those people are probably more attractive on average.
I wasn't implying that either, indicated by "as humans don't transfer to each other."
I painted a scenario where your environment would occur, and dispute it by saying those cats in that environment generally aren't infected
Unless those attractive people are hanging out in barns or patios with outside cats.
Now that could be the case if you go at it from an outdoors perspective, outdoorsy people may be more attractive on average, and they may encounter infected cats more on average.
Most cat owners I know have inside only cats, as do I. I do know of 3 cats that roam my neighborhood, they could be from quite far away as outdoor cats have a large range.
I guess anecdotes from you or I isn't really telling if an indoor or outdoor majority of cat ownership is "unrealistic". Maybe we need a study :p
Do outside cat owners generally let their cats inside their home?
Doesn’t matter, they’re domestic cats and you already explained a circumstance where they could expose visitors and owners. Half the year here is a hospitable climate for outdoor recreation and cat survival. Half of it isn’t. I have seen these cats for multiple years so unless they have an outdoor cat house (something I have never seen in my life) then I suspect they come inside.
The ratio of cat owners with outdoor cats is irrelevant. They exist and they are common. That’s enough to sink your assertions.
I don’t understand why you keep mentioning hooking up, that seems irrelevant since it’s been clarified this is not an STD. The parent comment was saying people who own cats could be more attractive on average, and people who own cats are more likely to get toxoplasmosis.
> Attractiveness and having a larger number of partners, which increases odds of exposure to cats
Hooking up was simply an example of why the person would be at the other person's environment.
Replace it with getting together if you're getting hung up on it. Whether or not the humans met up to have sex, talk, stand on their head, or whatever is irrelevant.
The point was house cats generally don't eat infected mice, if you're hanging out in barns or on the patio with outside cats, sure maybe.
Just want to note that kibble is not the best of foods for cats, especially not as the only food: it tends to cause urinary blockages which are a veterinary emergency.
I think the research is still incomplete on human to human transmission looking at some of the commenter's research article links.
It looks like it CAN spread via sex.
I think the point of the article disagrees with you? Like, to my reading, the hypothesis is that T. Gondii should be under selective pressure to support its host mating, because that aids its spread.
From the background paragraph:
> However, if parasites diminish a host’s health and attractiveness to such an extent that finding a mate becomes almost impossible, the parasite would decrease its odds of reproducing and passing to the next generation. There is evidence that Toxoplasma gondii (T. gondii) manipulates phenotypic characteristics of its intermediate hosts to increase its spread.
And the conclusions paragraph:
> Our results suggest that some sexually transmitted parasites, such as T. gondii, may produce changes in the appearance and behavior of the human host, either as a by-product of the infection or as the result of the manipulation of the parasite to increase its spread to new hosts. Taken together, these results lay the foundation for future research on the manipulation of the human host by sexually transmitted pathogens and parasites.
It's hard to read that as anything other than the authors classifiying T. gondii as a "sexually transmitted parasite".
I don't know how to reconcile that with what you're saying. Am I missing something?
Contrary to what you wrote about T. gondii definitively not being sexually transmitted between humans, the article links to several studies which postulate exactly that. The paragraph is:
> Since reports that T. gondii can be a sexually transmitted parasite in humans are relatively recent (e.g., Flegr, Klapilová & Kaňková, 2014; Hlaváčová et al., 2020; Kaňková, Hlaváčová & Flegr, 2020; Tong et al., 2021), many questions and hypotheses still need to be properly formulated and tested in further studies.
The basis for this theory is that T. gondii cysts have been found in human ejaculate, which means it could for example be transmitted through oral sex. There does not appear to be any conclusive proof that this has happened, but apparently these are viable cysts which, if swallowed in any other context, would result in infection, so it's plausible.
This non-"pregnancies, organ transplants or cannibalism" route is the basis for a lot of this article's theorising about T. gondii benefiting from raising its host's likelihood of having sex.
Our results suggest that some sexually transmitted parasites, such as T. gondii, may produce changes in the appearance and behavior of the human host, either as a by-product of the infection or as the result of the manipulation of the parasite to increase its spread to new hosts. Taken together, these results lay the foundation for future research on the manipulation of the human host by sexually transmitted pathogens and parasites.
Agreed. I think it’s far more likely that the lifestyle differences between more and less attractive individuals is causing increased exposure. Not to mention they performed a LOT of tests without correcting for multiple comparisons (as far as I could tell by skimming). Overall pretty disappointing.
Being infected with toxoplasma is know to increase reckless behaviour. Having sex with lots of people can be seen as reckless behaviour. Using that argument the conclusion is somewhat reasonable.
Another one I have thought about is HPV virus(or other sexualy transmitted illnesses) and your desire to have sex. There should be a strong evolutionary pressure for the virus to increase your sex drive. If it does, I don't know.
Recklessness in men, is, by its very nature, sexy[0]. Whether toxoplasma became genetically lucky (i.e., trait that is immediately genetically stable after a few mutations) or if evolutionary pressure created this effect (i.e., many generations where this trait grows over time) may be impossible to ever know.
Edit:
Downvotes, again? Added a reference. A scientific claim about evolutionary psychology can have merit even if it doesn't fit your personal hopes for the human race. Furthermore, in what world do the downvoters live where women are more likely to causally sleep with the cautious inconspicuous male vs the reckless bad-boy.
The referenced study is weird[0]. It uses smoking and drinking as a proxy for recklessness in men, but doesn't seem to take into account at all whether the women who were evaluating the men smoked or drank themselves. It's like it forgot it was specifically about smoking and drinking, not recklessness.
Smoking and drinking women young women (<30) would intuitively find smoking and drinking men more attractive for a short term thing, and find that behavior less acceptable for the long term as they probably find it less acceptable for themselves in the long term. Somebody else did this analysis with smokers, but didn't treat the women as fungible[1]. They found the heightened attraction to smokers was limited to smokers.
IMO, we don't really need explanation for why reckless (i.e. brave, risky decisionmaking) people have more short-term relationships. They're more willing to proposition people (brave), and more willing to sleep with people who they will ultimately decide they actually don't like (risky decisionmaking.) This is by definition, as valid if not more than the use smoking and drinking as a definitive sign or recklessness.
I'm not saying that people who smoke and drink are more likely to make brave and risky decisions when it comes to interactions with potential sexual partners, but both sets of behaviors can be called "reckless."
> in what world [are] women are more likely to causally sleep with the cautious inconspicuous male vs the reckless bad-boy.
The world in which the cautious inconspicuous male approached her, and the reckless bad boy didn't. Reckless behavior in women is also attractive, but it isn't due to conforming to some chad stereotype; it's due to the fact that if a woman makes bad decisions, sleeping with you might be one of them.
Even suggesting that facial assymetry in adults, which takes decades to develop, is reduced by a parasite, is an extremely extraordinary claim, that requires far more evidence than this.
What plausible mechanism is there for the body to even detect asymmetry and then change it? Your brain can't make your ear move lower.
Well, I for one believe and amuse myself with the findings of this paper. It reminds us that nature is not a divinity of perfection working in our favor (if anybody had any doubt at this point, that is).
It is clear that parasites do change our genome and how we express our genes in order to further transmit themselves. It would not be surprising that good looks, lower body fat, etc increases sexual contact and therefor transmission.
Man that's some fucked up shit. I'd bet you'll see Kardash-clone ladies putting catshit flakes on their cereal to get, "lean'd." I think it's important to note the apostrophe, "d."
75 comments
[ 3.1 ms ] story [ 145 ms ] threadThere's no space after the comma and the commenter is putting two values in a single variable which normal holds an integer
"Our results suggest [...] these results lay the foundation for future research"
Its the classic do an easy little study, and suggest that the potential for results might point to further studies. Now you have something to tell your research coordinator next time they get in your hair.
Interesting idea, I am not convinced right now - but let's see if it reproduces.
https://en.m.wikisource.org/wiki/The_Book_of_Were-Wolves
More sexual mates is riskier, living athletic/outdoorsy/"active" lives is also more risky than being a couch potato...
I don't think we're breaking new ground in saying the risk-averse tend to be less sexually attractive.
That is expressing caution.
How else would you like them to state that without being overly verbose?
"Our results suggest that some sexually transmitted parasites, such as T. gondii, may be correlated with appearance and behavior of the human host."
I appreciate your viewpoint. I would counter it by saying that there are two sources of uncertainty here: choice of model & sampling variance. It's my opinion that in scientific writing, one should be precise with which source of uncertainty they are guarding. If I'm allowed to group these together, why can't I make a similar statement of causation of any old spurious correlation - when obviously my model is bad?
Considering this example again - isn't it arbitrary that the authors get to choose which hypothesis (among many, like attractive people being predisposed to own cats) they get to claim "may" be demonstrated?
Similar line of discussion: https://statmodeling.stat.columbia.edu/2015/04/04/thinking-p...
But that is a different statement. They say that they found correlation and there may be causation. You say there may be correlation, a much weaker claim.
> Considering this example again - isn't it arbitrary that the authors get to choose which hypothesis (among many, like attractive people being predisposed to own cats) they get to claim "may" be demonstrated?
Of course it is arbitrary. But that was their hypothesis and you have to start with some hypothesis, no? They gathered data to establish correlation between the infection and attractiveness. They didn't gather data for anything else, so I think it's pretty reasonable to say we found correlation and further research might be interesting to see if there is causation.
Literally the next sentence says "Taken together, these results lay the foundation for future research".
If you go beyond the abstract and into the actual article, they are pretty careful to just list possibilities for the observed correlation. They certainly could have stated that it might just be spurious correlation there, but I don't blame them too much. These articles are supposed to be concise and not verbose and especially the abstract is supposed to be as concise and short as possible.
I agree with your general premise and the linked article though. It should be a given to consider that and ideally also state it in the article.
https://academic.oup.com/aje/article/190/3/386/5905708 https://pubmed.ncbi.nlm.nih.gov/24986706/
T. Gondii reproduces in felines, and is transmitted initially through their feces to other hosts. Humans catch it most often through infected food (meat, vegetables) or liquids (water, milk). Humans cannot transmit T. Gondii to other humans, unless pregnancies, organ transplants or cannibalism are involved.
So, regardless of how attractive an host is, he won't have more or less opportunities to be infected with T. Gondii than anyone else. This is not a STD.
Unless there is some sort of correlation between attractiveness and eating poorly corked meat.
Even then you'd have to infect yourself with the cat while getting together, as humans don't transfer to each other.
Personally I don't think there's any causation here at all with attractiveness directly.
It may be correlated with more outdoorsy people, those people are probably more attractive on average.
I painted a scenario where your environment would occur, and dispute it by saying those cats in that environment generally aren't infected
Unless those attractive people are hanging out in barns or patios with outside cats.
Now that could be the case if you go at it from an outdoors perspective, outdoorsy people may be more attractive on average, and they may encounter infected cats more on average.
Your characterization of cat ownership is unrealistic.
I guess anecdotes from you or I isn't really telling if an indoor or outdoor majority of cat ownership is "unrealistic". Maybe we need a study :p
Do outside cat owners generally let their cats inside their home?
The ratio of cat owners with outdoor cats is irrelevant. They exist and they are common. That’s enough to sink your assertions.
> The ratio of cat owners with outdoor cats is irrelevant.
It's extremely relevant when talking about a large enough scale of infection to support the attractiveness causation hypothesis posed by GP.
> I have seen these cats for multiple years so unless they have an outdoor cat house (something I have never seen in my life)
Outdoor cats generally stay underneath the house / porches, cars, etc. during cold or especially hot weather.
> That’s enough to sink your assertions.
I'm disputing the above proposed hypothesis on the grounds I don't think it's common enough occurrence and we're lacking information.
Hooking up was simply an example of why the person would be at the other person's environment.
Replace it with getting together if you're getting hung up on it. Whether or not the humans met up to have sex, talk, stand on their head, or whatever is irrelevant.
The point was house cats generally don't eat infected mice, if you're hanging out in barns or on the patio with outside cats, sure maybe.
(phew.. I'm male)
> organ transplants
(none needed yet)
> or cannibalism are involved.
(oh, NO!!!!!)
From the background paragraph:
> However, if parasites diminish a host’s health and attractiveness to such an extent that finding a mate becomes almost impossible, the parasite would decrease its odds of reproducing and passing to the next generation. There is evidence that Toxoplasma gondii (T. gondii) manipulates phenotypic characteristics of its intermediate hosts to increase its spread.
And the conclusions paragraph:
> Our results suggest that some sexually transmitted parasites, such as T. gondii, may produce changes in the appearance and behavior of the human host, either as a by-product of the infection or as the result of the manipulation of the parasite to increase its spread to new hosts. Taken together, these results lay the foundation for future research on the manipulation of the human host by sexually transmitted pathogens and parasites.
It's hard to read that as anything other than the authors classifiying T. gondii as a "sexually transmitted parasite".
I don't know how to reconcile that with what you're saying. Am I missing something?
> Since reports that T. gondii can be a sexually transmitted parasite in humans are relatively recent (e.g., Flegr, Klapilová & Kaňková, 2014; Hlaváčová et al., 2020; Kaňková, Hlaváčová & Flegr, 2020; Tong et al., 2021), many questions and hypotheses still need to be properly formulated and tested in further studies.
The basis for this theory is that T. gondii cysts have been found in human ejaculate, which means it could for example be transmitted through oral sex. There does not appear to be any conclusive proof that this has happened, but apparently these are viable cysts which, if swallowed in any other context, would result in infection, so it's plausible.
This non-"pregnancies, organ transplants or cannibalism" route is the basis for a lot of this article's theorising about T. gondii benefiting from raising its host's likelihood of having sex.
Our results suggest that some sexually transmitted parasites, such as T. gondii, may produce changes in the appearance and behavior of the human host, either as a by-product of the infection or as the result of the manipulation of the parasite to increase its spread to new hosts. Taken together, these results lay the foundation for future research on the manipulation of the human host by sexually transmitted pathogens and parasites.
Another one I have thought about is HPV virus(or other sexualy transmitted illnesses) and your desire to have sex. There should be a strong evolutionary pressure for the virus to increase your sex drive. If it does, I don't know.
Edit: Downvotes, again? Added a reference. A scientific claim about evolutionary psychology can have merit even if it doesn't fit your personal hopes for the human race. Furthermore, in what world do the downvoters live where women are more likely to causally sleep with the cautious inconspicuous male vs the reckless bad-boy.
[0] https://www.thetimes.co.uk/article/reckless-men-are-more-lik...
For something to be of its very nature it has to be part of that thing.
No reference in the world can make one thing in to another.
Smoking and drinking women young women (<30) would intuitively find smoking and drinking men more attractive for a short term thing, and find that behavior less acceptable for the long term as they probably find it less acceptable for themselves in the long term. Somebody else did this analysis with smokers, but didn't treat the women as fungible[1]. They found the heightened attraction to smokers was limited to smokers.
IMO, we don't really need explanation for why reckless (i.e. brave, risky decisionmaking) people have more short-term relationships. They're more willing to proposition people (brave), and more willing to sleep with people who they will ultimately decide they actually don't like (risky decisionmaking.) This is by definition, as valid if not more than the use smoking and drinking as a definitive sign or recklessness.
I'm not saying that people who smoke and drink are more likely to make brave and risky decisions when it comes to interactions with potential sexual partners, but both sets of behaviors can be called "reckless."
> in what world [are] women are more likely to causally sleep with the cautious inconspicuous male vs the reckless bad-boy.
The world in which the cautious inconspicuous male approached her, and the reckless bad boy didn't. Reckless behavior in women is also attractive, but it isn't due to conforming to some chad stereotype; it's due to the fact that if a woman makes bad decisions, sleeping with you might be one of them.
[0] https://journals.sagepub.com/doi/full/10.1177/14747049166316...
[1] https://www.researchgate.net/publication/263849372_Can_cigar...
This parasite alters sexual behavior in rats, could this be altering people's behavior not just their appearance as well?!
What plausible mechanism is there for the body to even detect asymmetry and then change it? Your brain can't make your ear move lower.
New sexual strategies are need I suppose.