Dave Snowden is all freaked out about how parasites can influence the behavior of their infected hosts—even humans and human cultures. According to Proceedings of the National Academy of Sciences, (nicely summarized by LiveScience on MSNBC) a unicellular organism “precisely alters fear.” Toxoplasma gondii causes rats to be attracted to—rather than fear—the smell of cats because T. gondii’s life cycle requires both animals. The rats get it by eating cat feces and the cats get it back by eating the rats. Changing the behavior of the rats presumably facilitates both transfers. It does not otherwise endanger their survival because it leaves their other instinctual fears alone.
Here’s the thing: up to 80% of humans are also infected by T. gondii at one point or other in their lives. There can be serious physiological consequences, but apparently psychological ones, too.
As explained in Neurophilosophy
Nicky Boulter, a research fellow at the Institute for Biotechnology of Infectious Diseases, at the University of Technology in Sydney, Australia, summarizes the findings: Infected men have lower IQs, achieve a lower level of education and have shorter attention spans. They are also more likely to break rules and take risks, be more independent, more anti-social, suspicious, jealous and morose, and are deemed less attractive to women. On the other hand, infected women tend to be more outgoing, friendly, more promiscuous, and are considered more attractive to men compared with non-infected controls.
Many parasites alter the behavior of their hosts. For example, the aggressive behavior of rabid animals, for example, is not a simple side effect of infection either, but the best way for the virus to spread—through saliva when the animals bite others.
For more than you ever wanted to know, see Parasite Rex: Inside the Bizarre World of Nature’s Most Dangerous Creatures by Carl Zimmer (see his blog, The Loom).
Dave wonders what would happen if religious fanatics (or management consultants) ever got hold of the technology. (This already features in science fiction, such as Vernor Vinge’s Rainbow’s End.) You can certainly wonder what has gotten into American conservatives who want to block new vaccines that can slow the spread of the human papillomavirus, which is spread by sexual activity and causes some 1.8 million cases of cancer per year in the US alone.
But don’t worry Dave, we’re not nearly as smart as parasites.
Zimmer writes about all kinds of parasites: viral, protozoan, etc. Others write about memes as idea viruses that certainly affect individual and collective cognition.
I used to have this idea about capitalism that money essentially behaves as a virus, infecting a host economy, multiplying, and then swarming back out to find new hosts through overseas investment or capital flight. Money certainly changes people’s behavior in ways that spread the “disease.”