No, Dummy, Scientists Didn't Find A Stupidity Virus
Some rather alarming media accounts yesterday proclaimed the discovery of a virus that makes people stupid – though as far as I can tell, no actual scientist used the word stupid, which is not precise enough to qualify as a scientific term.
The announcement that spawned the headlines actually appeared in the scientific literature on October 27. The paper, published in the Proceedings of the National Academy of Sciences (PNAS) got little attention then, mostly because the scientists didn’t think to call it a stupidity virus.
What the Johns Hopkins University scientists found was that in a small sample of 90 people, some 43% harbored a virus called chlorovirus ATCV-1 in their throats. Though we’re all colonized by viruses and bacteria that don’t make us sick, this was of interest for two reasons. First, it was previously known to infect algae, and viruses aren’t thought to jump easily from one kingdom of life to the other. And secondly, they found a very small correlation between infection and performance on a couple of cognitive tests. Infected subjects appeared to be slower at processing visual information.
In another part of the study, the scientists showed that mice deliberately infected with the virus were slower to solve certain puzzles – thus lending some backing to their interpretation that the virus is having some effect on certain mental abilities.
Purdue University virologist David Sanders said he would need to see this replicated before he’d believe the claim. One possible problem is the possibility that samples from the patients might have been contaminated with the algae virus. Contamination wrongly led scientists a few years ago to link a virus called XMRV to chronic fatigue syndrome. “That was a total disaster,” he said.
He also raised questions about the peer review behind the paper. The journal, PNAS, allows authors to choose their own reviewers in some cases. “Something is wrong here…I don’t know how the experiments happened,” he said. “This is a whole bunch of random data stitched together with little real basis for making any conclusions.”
It’s provocative, and perhaps worth a follow up study, but unlikely to have implications for human stupidity. What’s fascinating is that if confirmed, the findings hint that some of those seemingly harmless viruses or bacteria that live with us could have a subtle influence on us after all. We’re already getting data suggesting that your intestinal bacteria influence your tendency to store excess fat.
There are also hints that a common parasitic infection called toxoplasmosis could change people’s personalities or put them at higher risk of mental illness. The parasite is acquired from contaminated food, water, soil or from scooping the litter used by an infected cat – hence a spate of recent headlines along the lines of “Is your cat making you crazy.”
There are other infectious agents that can cause mental illness – syphilis and rabies, to name two. But those are pretty obvious diseases. There’s something about stealthy agents influencing us that seems to cause a lot of angst.
But what made this algae virus news go viral was the decision on the part of someone to frame it as a “stupidity virus”. Here’s Wired, for example:
Researchers at the John Hopkins Medical School and the University of Nebraska have discovered a virus that infects our brains and “makes us more stupid.”
What’s misleading here is the story never reveals who is being quoted saying “makes us more stupid.” The implication is that it’s the scientists or someone in authority. But there’s no such phrase in the paper or the press release from Johns Hopkins University, nor does the story seem to include an interview.
The source may have been Newsweek with its story, “American Researchers Discover Stupidity Virus.” It says:
American scientists have located a virus that attacks human DNA, which may cause those infected to be less intelligent, impairing brain activity, learning and memory.
This is not exactly what the study said. For one thing, as Sanders pointed out, the virus doesn’t attack human DNA and the researchers never make that claim in the paper.
Why would the researchers even think to look for an effect on cognitive traits? The paper said that since the cohort being tested was taking part in a cognitive study, the scientists had a bunch of cognitive data available.
Because the individuals in the study cohort were also participating in a study of cognitive functioning (15), we examined the association between detection of ATCV-1 DNA and performance on a battery of cognitive tests.
They found statistically significant but very small difference on several of the tests – including measures of visual information processing speed and attention. I couldn’t find the word “stupid” in any form, and the only time I could find the word “intelligence” was when the researchers admitted that infected and uninfected scored the same on a test called the Wechsler Adult Intelligence Scale.
It may be there was no real hypothesis being tested but that the study is what scientists call a fishing expedition. Those can be useful for generating hypotheses to be tested but any correlations they turn up need to be confirmed.
Studies of this type can lead to spurious correlations through a problem called the multiple testing effect or the look elsewhere effect, depending on the field. If scientists are fishing through a large number of possible correlations, they increase their odds of finding some kind of pattern. Think about how unlikely it is to get 7 heads in a row if you flip a coin seven times. Now think about how likely it would be to get seven heads in a row eventually if you tossed the coin 1000 times. If you have a group of people with the infection and without, and you test them on enough things, some differences will inevitably turn up by chance.
Studies of this type can lead to spurious correlations through a problem called the multiple testing effect or the look elsewhere effect, depending on the field. If scientists are fishing through a large number of possible correlations, they increase their odds of finding some kind of pattern. Think about how unlikely it is to get 7 heads in a row if you flip a coin seven times. Now think about how likely it would be to get seven heads in a row eventually if you tossed the coin 1000 times. If you have a group of people with the infection and without, and you test them on enough things, some differences will inevitably turn up by chance.
That may not be the case here. It’s possible that this common virus is having a deleterious effect. Scientists should follow up this with a bigger study. The fact that some huge portion of the population (at least in Baltimore) carries this virus is surprising. There seems to be little understanding of how one acquires it – or avoids it. Nor does anyone seem to know how long it’s been tagging along with people or how it ever got from algae to people. It’s worth a closer look.
