Pardon the sensationalist headline of that article:

Mark says that "one thing that might explain the higher numbers here—in case people question my methods—is that I used a tarantula." Apparently, people seemed pretty eager about hitting a spider. "If you take that out it goes to 2.8% which is closer to the other turtle vs. snake studies I ended up finding."

It is still quite a surprisingly high number. At least compared to a 2008 study using the Psychopathy Checklist, which discovered that 1.2 percent of the US population were potential psychopaths. 1.2 vs 2.8 is a huge difference.

I was not aware of the other turtle and snake studies.

Note that with turtle this is the lower bound on percentage of evil; a perfectly amoral person that could e.g. kill for modest and unimportant sum of money or any other reason would still have no incentive to steer to drive over a turtle; and a significant percentage of people would simply fail to notice the turtle entirely.

This gives interesting prior for mental model of other people. Even at couple percent, psychopathy is much more common than notable intelligence or many other situations considered 'rare' or 'unlikely'. It appears to me that due to the politeness and the necessary good-until-proven-evil strategy, many people act as if they have an incredibly low prior for psychopathy, which permits easy exploitation by psychopaths. There may also be signaling reasons for pretending to have very low prior for psychopathy as one of the groups of people with high prior for psychopathy is psychopaths themselves; pretending easily becomes too natural, though.

Perhaps adjusting the priors could improve personal safety and robustness with regards to various forms of exploitation, whenever the priors are set incorrectly.

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Wait, a test using a turtle to determine if someone has decent, normal human reactions? Really?


"You're driving in the desert, and on the shoulder of the road ahead you see a turtle..."

Oh, I thought you meant that turtle.

"Urgh, someone posted some research without posting a link to the original paper. I better go find it...'s a youtube video."

The approx 2% figure is interesting to me. This seems to be about the right frequency to be related to the small minority of jerks who will haze strangers for sexist and/or racist motivations.

This might be related to the differences in the perception of the prevalence of racism between minorities and mainstream members of society. If one stands out in a crowd, then one can be more easily "marked" by individuals seeking to victimize someone vulnerable. This is something that I seem to have observed over the years, though I have not taken the time to gather hard data.

Basically, if one has a noticeable and salient difference, one will tend to attract more than one's share of attention from "jerks." Though such events are uncommon, they will happen often enough that the possibility always lurks in the back of one's mind. This results in a noticeable cognitive difference between minorities and mainstream persons.

Considering he deliberately chose creatures he -expected- people to run over, I don't think this experiment shows what the quote says it shows. Your response implies you already suspect reasons why somebody would run over snakes and spiders, and the turtle-squashing percentage was apparently 1%, which comes in less than the expected number, if we presume psychopaths want to run over turtles. But now I'm curious about the frequency of people with visceral reactions to turtles.

I agree. Snakes are a poor choice of animal for a psychopathy test.

If I see a snake anywhere near my house, a friend/relative's house, or in a nearby park, then I will go out of my way to grab a shovel or something and kill it. I will not risk some child or someone I know getting bitten by one, and I'm not skilled enough to distinguish which ones are poisonous or potentially harmful to humans so they all go.

A better title would be "5% of people go out of their way to kill dangerous scary animals, 1% are psychopaths as usual."


And at least one person considers snakes and the time to kill them less valuable than the time it takes to identify dangerous snakes and not kill harmless or beneficial snakes.

Replace 'snake' with 'human' and '[venomous] or potentially harmful to me' with 'kittens' and 'rabid', you might realize that the ick factor of reptiles is more important to you than the actual danger.


I squash bugs for the hell of it sometimes. Squashing things can be satisfying. I guess that means I'm a psychopath (really should be sadist, right?) too?

It certainly feels like I empathize with people at times, and my goals are quite altruistic. But I don't empathize much with bugs. I'm a little skeptical they feel anything that I would classify as pain. How much nervous tissue do they have, really?

Could you put me in a situation where I had the same kind of lack of empathy for larger creatures or even humans? Possibly. I don't have strong inhibitions against this mindset, but that may be because I don't have strong inhibitions against "forbidden thoughts" in general. For example, I don't revile pedophiles like you're supposed to in US culture. (Although this may not be a very high bar relative to LW.)

Note also that this is my alt account, soon to be deleted. Maybe other reasonable, friendly people without alt accounts would also squash bugs but are afraid of explaining themselves for fear of being labeled sadists.

Squashing things can be satisfying.

Yeah, but when I'm in such a mood I usually use plastic glasses.

When I was in my early teens, I knew lots of people my age who would torture lizards just for the fun of it.

This is no more a scientific experiment than what they do on Myth Busters. You should not be making any conclusions whatsoever from it, let alone anything about mental health of general population.

I agree that's not terribly strong evidence, but it's evidence nevertheless.

I wonder if some of the influence was from the family trip in The Great Santini?

I really, really want to repeat this test with something furry. Anybody know of an affordable toy mammal that might withstand getting hit by an SUV repeatedly?

I once hit some sort of large bird on the highway when it flew directly into my lane from a cluster of bushes off the shoulder. It was so close to me when it entered my lane that all that registered was "white, flying." There was no way I could have avoided hitting it, but I had to pull off the road to bawl over it for a few minutes. I don't expect people to react the same way I did, but I definitely expect them to not intentionally kill roadside wildlife.

EDIT: It would also be a great idea to run a test with a fake cat. People have all sorts of reasons for discounting the suffering of animals, but it would be very, very difficult to justify killing something that is somewhat likely to be someone's beloved pet. It would also be more visible than a tarantula, snake, or turtle, which might prevent the number of hits from being deflated as the result of a certain percentage of drivers not seeing the dummy at all.

Leaving people to believe they just killed a cat, maybe to regret it later, isn't being kind to the people.

As with the original experiment, the "cat" would be far enough onto the shoulder that it would only be hit if the driver intentionally swerved off of the road. For safety reasons (and to reduce confounds), I'd set it up on a straightaway with wide lanes.

Frankly, if someone is going to regret making the decision to deliberately harm an animal, I'd rather they have their change of heart after "killing" a dummy and not the real thing.

Does this mean that a lot of the road kill I see is actually deliberate? Because, as a distance runner, that would kinda piss me off. Forget about the animals: why would you go out of your way to create a mess that other people have to deal with? Is there any other explanation for this behavior? (Maybe they were just trying to scare the animals away? Or trying to kill them before they made it into the road, reasoning it would be safer?)

Inferring rates of psychopathy from someone's desire to kill small animals seems subject to a variety of confounding factors - most notably, many people feel little or no empathy for (some) animals, not because they are incapable of feeling empathy, but because of their model of animals does not feel pain (because they aren't conscious, and I don't feel pain when I'm unconscious!)

Our society is unusually empathetic towards animals; remember, setting a cat on fire was a popular form of entertainment in the middle ages! Not to mention cock-fighting, bear-baiting, and that thing where they put a bunch of rats in a pit with a dog and place bets on how long they'll last ... whatever that was called.

An example would, of course, be this commenter