RACHEL MARTIN, HOST:
As the planet gets hotter, students around the world are dealing with more sweltering days and warmer nights. Does this have any effect on how well they learn? Shankar Vedantam, the host of the Hidden Brain podcast, joins us regularly on this program. He is here with us now to ponder this very question. Hi, Shankar.
SHANKAR VEDANTAM, BYLINE: Hi, Rachel.
MARTIN: All right. Heat and learning - explain the connection.
VEDANTAM: Well, researchers have long studied how temperature extremes can affect learning and human behavior, Rachel. Anyone who's shivered or sweltered through a lecture knows that we humans are like Goldilocks. We don't like it too hot, and we don't like it too cold. In a new analysis of about 10 million U.S. students over 15 years, Jisung Park at UCLA and his colleagues find that climate change may indeed be affecting learning and test scores. Here he is.
JISUNG PARK: Students who experience a hotter than average year - let's say a year with five more days - school days above 90 degrees Fahrenheit - appeared to experience reduced learning. A 1 degree Fahrenheit hotter than average year - it looks like it reduces learning on average by around 1%. But for underrepresented minorities, we're talking more like 2% or 3%.
MARTIN: So how do we know that reduced learning is caused by the heat and not something else?
VEDANTAM: That's a good question, Rachel, because it's really raising the question of, how do you tell correlation from causation? The researchers did a number of things to disentangle these two things. They compared students from the same school in different years. Some years were hotter. Some years were cooler. They also compared how students did on a standardized test, the PSAT, against their own performance on the same test in a different year when it was hotter or cooler. Students often take the PSAT more than once.
Finally, they found that schools and communities were less affected by hot weather if they had air conditioning. So this might explain why students in poor communities were disproportionately affected by the warmer weather. Here's Park again.
PARK: When we look at schools that have and do not have AC, schools that appear to have more AC or have added more AC over time, we find that school air conditioning appears to help, right? The effect of heat on learning is much smaller in schools that report having adequate air conditioning.
MARTIN: So this is really a story about infrastructure, right? I mean, the schools that can afford air conditioning, their kids are going to learn better than the kids who are going to schools without it.
VEDANTAM: That is what the study is suggesting, Rachel. And, in fact, in the context of the COVID-19 pandemic, there's an additional wrinkle. If students are staying home during the academic year on account of the pandemic, a lack of air conditioning at home could also be a factor.
There are a couple of really interesting twists to the story that I should mention. It looks like schools in northern states seem to be more affected by hot weather, and this is possibly because many of those schools don't have AC already because they haven't anticipated that the planet is warming or that there are going to be a lot of hot days. The second thing is that if climate change is driving this, having more air conditioning that relies on fossil fuels for energy could help students learn better, but it could also inadvertently make the underlying problem worse.
MARTIN: NPR's Shankar Vedantam, the host of the Hidden Brain podcast. Shankar, thank you.
VEDANTAM: Thank you, Rachel.
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