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Michael: Earlier this month, a study announced that acetaminophen -- the painkiller found in medicines like Tylenol -- can make you less sensitive to the pain of others. So there have been a lot of headlines recently saying things like, “Tylenol Changes Your Personality!” But it’s a little too soon to be making those kinds of grand pronouncements.

The study did find that acetaminophen reduces empathy for pain, but this was just a first, exploratory study -- and one with sample sizes that were pretty limited. The researchers were studying a theory called "the simulation theory of empathy." The idea is that part of how we relate to others is by projecting our own mental state onto them -- essentially, we use our own experiences and emotions to understand and predict the behavior of others.

According to this theory, in order to feel empathy for other people’s pain, we need to activate some of the same mental processes we use to experience pain ourselves. There’s been some evidence for this theory from neuroimaging studies, which have shown that there’s overlap in the brain regions people activate when they experience pain and when they empathize with someone else’s pain. So the new study’s authors were curious if painkillers could reduce not only your own pain, but also your ability to empathize with the pain of others.

And the study found that they kind of do! In two separate experiments -- one with 80 participants, one with 114 -- people were asked to rate other people’s pain after finding out about it in different ways -- for example, through stories about other people dealing with painful things, like a death in the family. The subjects who had been given acetaminophen rated those experiences as less painful than those who had been given a placebo. This seems to support that simulation theory of empathy, but scientists still don’t know how acetaminophen could be reducing empathy in the brain. It’s easy to see why these findings seem so dramatic -- the study points out that almost a quarter of American adults use acetaminophen on a weekly basis, and if it’s affecting our ability to recognize the pain of others, who knows how it’s affecting our social interactions?

Still, this is just one paper, with about 200 subjects across two experiments -- and all of them were college students in introductory psych classes. So the results will need to be replicated in a larger, more diverse population, and it’s going to take a lot more research to understand how, exactly, acetaminophen affects the brain chemistry of empathy. And it’s definitely not proof that taking Tylenol changes your whole personality.

But other recent news could change the face of transportation. Last week, a startup called Hyperloop One ran the first successful test of a hyperloop propulsion system on a full-sized test track. Hyperloops -- originally proposed by Elon Musk -- still mostly conceptual. If they work, we’ll have a new type of transportation that can travel really fast, using magnetic levitation and vacuum tubes.

Hyperloop capsules would use magnets to hover slightly above the track, which would eliminate friction from rolling wheels. And the vacuum tubes would help get rid of a lot of that wind resistance. This would allow the vehicle to reach speeds of over 1100 kilometers per hour -- so passengers could travel from San Francisco to Los Angeles in about 35 minutes. There are a lot of companies working on this technology, and on May 11, Hyperloop One sent a test vehicle down a track just outside Las Vegas, at speeds of up to 480 kilometers an hour.

They were testing their propulsion system in what they called a propulsion open-air test. The propulsion system they were testing involves a linear electric motor, which uses electromagnetic forces to propel the test vehicle. But this test wasn’t a perfect one, because open air testing can’t replicate the partial vacuum you’d find in a real hyperloop tube. The actual hyperloop will need fewer motors across the same length of track, and should be able to get the vehicle moving at even higher speeds, once they’ve designed a more aerodynamic capsule.

And another thing they still need to design? The brakes. They had to send their test vehicle zooming straight into a pile of sand to get it to stop during this round of testing. So it’s pretty cool that the test went so well, but it’s going to be a while before we’re all riding around in hyperloops.

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