My Favorite Brain Parasite
Teddy Warner
| Dec 2025
| 5-7 mins
I’ve been on a bit of a toxoplasmosis (my favorite brain parasite) kick as of late and I think provides an interesting resolve to this. If you’ve ever seen one of those funny videos where a mouse chases after a cat you’ve probably seen toxoplasmosis at play - the parasite rewires the ‘fear cortex’ of the mouse to ‘sexual arousal’ - making them attracted to cat scent instead of scared of it.
The CDC claims that roughly 22% of Americans have chronic toxoplasmosis (which is nuts), and studies show that it roughly doubles traffic accident risk in humans, and I’d assume this is due to a similar rewiring of fear response we see in mice.1 2 One autopsy study found 59.5% of traffic fatality drivers tested positive which is just insane. 3
Imagine I started selling toxoplasmosis in pill form that would make you ~2x more risk tolerant (and thus a better entrepreneur!), would you take it? Overwhelmingly people say no when I ask this, that they feel comfortable with the general risk tolerance they have now. Presumably the potential tail end loss (dying from increased life-threatening, physical risk or the parasite itself) doesn’t equate to the upside of risk tolerance, even though taking the pill would almost certainly make them better entrepreneurs. I think segregating risk into a “bad” and “good” is probably the right idea, but the two are undoubtedly intertwined, and risk tolerance decreases as a whole.
As for more time for more ventures, this is almost certainly true, but I doubt it coxes more people into starting ventures, it simply allows those who do so a higher chance of success (and in turn a lower need for risk tolerance), as odds are you get something right over 100 years.
If you’re already the type of person willing to start ventures, having 1000 years dramatically improves your odds. Yet, given we probably can’t expect “good” risk tolerance to remain the same, while “bad” risk tolerance is plummets in a 1000-year lifespan society, i think it follows that the percentage of people willing to start ventures in the first place drops quite substantially. Footnotes
Enter your email to receive the occasional update.