You know what they say...

It's so hot I can't think, but it's OK because I saved this. Oh, and did I mention it's hot? Also, near-death experiences: you and me at 1 pm ET. And 7 other things worth your time.

I’ve been holding onto this one for a slow, hot day. That day was yesterday (and the day before, and the day before that).

Bottom line upfront: Do your coworkers seem a little slow on the uptake? Is your boss a little sluggish? Are your employees having a hard time doing things they'd normally accomplish?

And if you’re not working—say, you’re retired, unemployed, funemployed, or independently wealthy—have you noticed recently that the average brainpower of the average folks you run into has, well, fallen a bit below average?

There could be a simple reason, according to Harvard scientists: It's that it’s so hot in America right now that people are becoming stupid.

This is not just a joke; temperatures have soared over the last 4 to 5 days in many parts of the US. It was 89 degrees Fahrenheit yesterday in NYC with insane-level humidity; plus 86 in Boston, 83 in Chicago.

And if it hasn’t been that hot where you are lately—well, just wait.

Back to Harvard—specifically, the T.H. Chan School of Public Health, which reported on a scientific study concluding that, all else being equal, smart people become dumber when the temperature soars.

About 13% dumber, if we want to quickly put a number on it.

Here’s the data, published in the journal PLOS Medicine. Researchers tracked 44 college students in the Boston area during a 2016 heatwave (along with the period just before and just after the heatwave).

The students were all roughly the same age, attended the same college, and lived near each other.

The only identifiable difference was that about two dozen of the students lived in an air-conditioned dormitory that had been built in the 1990s. The remainder lived in a series of buildings that were about 50 years older and did not have air conditioning.

Each morning, just after they woke up, all the students were required to take two cognition tests on their smartphones:

  • One test was designed "to evaluate cognitive speed and inhibitory control," which is basically the ability to focus, according to a Harvard press release.

  • The other test "consisted of basic arithmetic questions and was used to assess cognitive speed and working memory."

During the heatwave, students who lived in buildings without air conditioning did 13.4% worse on the first test, and 13.3% worse on the second test, compared to the lucky kids living in the air-conditioned buildings.

Apparently stupidity sticks, because the biggest measurable difference in cognitive function between the students living with and without air conditioning was observed in the days right after the heatwave, "when outdoor temperatures began to subside but indoor temperatures remained elevated in the dormitories without air conditioning."

The researchers say all of this is important because climate change is going to precipitate more and more heatwaves around the world in years to come.

"Most of the research on the health effects of heat has been done in vulnerable populations, such as the elderly," said Jose Guillermo Cedeño-Laurent, a research fellow at Harvard’s Chan School and lead author of the study.

The problem with that focus, he said, is that it suggests the problem might not be that big a deal for the general population. Not so, they surmise after their study.

Of course, you probably don't need Harvard scientists to tell you that. Just look around and observe. And don’t blame yourself; don’t blame them.

Blame the weather. As they say, it’s not the heat; it’s the stupidity.

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Great turnout already for my upcoming interview at 1 pm ET with Dr. Bruce Greyson, author of After: A Doctor Explores What Near-Death Experiences Reveal about Life and Beyond.

We still have a few slots left, so if you’d like to participate, please sign up here. I sent calendar invitations to a bunch of people last night (if you’d signed up as of last night and didn’t receive one, email me). I’ll send the last batch out today at 12 pm ET.

(Paid members are guaranteed to be able to participate; free members can join on a space-available basis.) Check your notifications for the Zoom link!

Mistake yesterday: The woman whose twin sister fought off a crocodile was named Georgia. The attack took place in Mexico. (I’d said it happened in Georgia; you can see why I made the mistake, but it was still wrong. Also, it was hot when I wrote it.)

7 other things worth your time

Thanks for reading. Photo credit: Pixabay. I found this study and first wrote about it a while back on Want to see all my mistakes? Click here