On August 15th, 2018 we learned about

Anglerfish’s biolumincent bacteria retain a strange potential for independence

While they sport an impressive visage complete with bulbous eyes and a mouth full of spiny teeth, an anglerfish’s most famous feature doesn’t exactly belong to the fish itself. The small glowing bulb that hangs from a stalk growing out of the female anglerfish’s forehead only lights up because it houses a colony of bioluminecent bacteria. As these bacteria light up, they attract potential prey and mates for the fish, although the exact details of how both organisms benefits haven’t been fully explored. Even after sequencing the bacteria’s DNA, it would seem that the relationship may be a bit more complicated than your average bit of symbiosis.

Most symbiotic relationships involving bacteria fall into one of two categories. In the first, a host offers a home or other benefits to the partner organism, but that partner remains free and unchanged from it’s uncoupled counterparts. The second form of bacterial symbiosis includes significant changes to the bacteria’s DNA. Thanks to services supplied by their host, they no longer need to maintain all their own bodily functions, and can be absorbed to live in a hosts own cells. A widespread example of this kind of relationship is the chloroplasts in plant cells that are essentially cyanobacteria living as organelles in plants, enabling photosynthesis.

Incomplete integration

The genome of the bioluminencent bacteria in anglerfish suggests an unusual third option that seems to operate as a half-way point between the relationships described above. The bacteria have apparently been shedding some of their genes over time, but not as many as you might expect from an organism tied so closely to a 100 million-year-old fish like the anglerfish. Instead of being completely independent or assimilated, these glowing bacteria may be hedging their bets somehow, retaining some of the genes found in their free-swimming kin found elsewhere in the ocean. For example, they’ve lost the genes to allow them to detect all food sources but one. They can’t make their own amino acids, but they do still have the genes necessary to grow the tail-like appendage called a flagellum that enables other bacteria to swim through the water.

Overall, both the fish and bacteria are still helping each other. The bacteria help attract things the fish needs, and the fish then houses and helps feed the bacteria nutrients they can no longer come up with on their own. Still, researchers are curious how this particular balance came to be, and if it’s still a work in progress that will eventually leave the bacteria more fully integrated into the anglerfish’s own body.

Source: Glowing bacteria on deep-sea fish shed light on evolution, 'third type' of symbiosis by Krishna Ramanujan, Phys.org

On August 15th, 2018 we learned about

The edge of our solar system is likely marked by light from particle collisions

My nine-year-old daughter can’t get over the fact that, as of now, we can’t detect any boundary to the universe. Sounding a bit like a mesmerized stoner, she rarely misses an opportunity to mention how much it blows her mind to try to imagine a borderless universe. So she’ll be either relieved or disappointed to learn that unlike the vast expanse of the entire universe, our solar system does have a border. What’s more, unlike the imaginary political borders humans draw on maps, our solar system’s edge is likely defined by a physical ‘wall’ of faintly-glowing hydrogen atoms.

The space filled by solar wind

This model is based on the idea that our Sun is constantly emitting not just light and heat, but charged particles as well. These high-speed protons, electrons and other ions that are blasted out of the Sun’s corona are collectively called solar wind. Solar wind isn’t emitted at a perfectly regular rate, but there’s enough of it being pushed out across the solar system that it’s almost like the Sun is inflating a large bubble from the inside.

That bubble is called the heliosphere, and seems to have a definable edge. 100 times further than the Earth is from the Sun, solar wind starts to encounter stray hydrogen atoms from outside the solar system. These neutral, interstellar atoms provide just a bit of resistance to the solar wind, and the two types of particles collide often enough to create a detectable amount of ultra-violet light. The meeting area between stray particles probably isn’t the most clear-cut boundary you might imagine, but the area where our Sun’s output meets objects from outer space should at least be directly observable.

Spotted by spacecraft

This light from the edge of the heliosphere, or heliopause, was first detected by the Voyager 1 spacecraft 30 years ago when that craft exited the solar system. Voyager 2 is seeing similar evidence, although it won’t actually cross the heliopause until 2030. The New Horizons spacecraft has started picking up traces of evidence that further support those observations, even though it’s still in the Kuiper belt.

The clearest proof of this model would be attainable when a spacecraft passes through the heliopause. Once on the other side, the ultraviolet light would immediately drop off, sitting squarely behind something like Voyager 2 as it continues to travel away from the Sun. Scientist note that this may not turn out to be the case, and that there may be an unknown source of ultraviolet light in the space beyond our solar system. However, with New Horizons backing up what has previously been found by Voyager 1 and 2, there is a strong likelihood that our Sun’s sphere of influence does a pretty good job of marking itself at the edge of the solar system.

Source: New Horizons may have seen a glow at the solar system’s edge by Lisa Grossman, Science News

On August 13th, 2018 we learned about

Conditioner makes hair manageable by coating cuticles in protective, fatty molecules

Between weekly swim lessons, ballet classes, misplaced food and the occasional lice infestation, my kids’ hair has taken a fair amount of abuse in the last few years. Since my daughter still hasn’t taken up my offer for a buzz-cut, there’s always a lot of griping about snarls and tangles when she needs to brush her hair. Aside from cutting back on exposure to heat and other activities that may dry hair out, the main tool to smooth things over has of course been hair conditioner. The white goop has seemed rather miraculous at times, removing tangles faster than even an hour of brushing. This naturally raised a few questions from my daughter— can conditioner replace brushing out snarls (no), and what exactly is conditioner doing in the first place?

Hair shaped by its outermost structures

To make sense of hair conditioner’s ability to make hair seem smoother and shinier, you need to first think about what a hair looks like on microscopic level. Hair is made up of the same class of proteins, called keratin, that make up your fingernails, rhinos’ horns and birds’ feathers. Obviously your hair doesn’t feel like these other bits of anatomy, which is largely thanks to the structure of a hair. At a hair’s core is medulla, which is then covered by a cortex, which is in turn covered by an outer, flaky-looking layer called the epicuticle. It should be noted that none of these structures are made of living cells, which means that their “health” is a non-factor in how your hair behaves. So instead of helping hair repair itself from damage, hair products like conditioner instead help patch things up from the outside.

The epicuticle is the key to a lot of your hair’s behavior and appearance. It’s a layer of overlapping flakes of protein, arranged a little like somewhat uneven shingles on a house. Ideally, your scalp produces the right amount of an oil called sebum to help coat and arrange the pieces of epicuticle so that they lay as flush along the shaft of the hair as possible, creating something like a single, uninterrupted surface. However, when your hair becomes dried out by something like heat from a blow dryer, the epicuticle flakes start to separate, turning the hair into a rough surface that is better at holding static electricity for frizzies, getting hooked on other hairs for tangles, and generally looking duller overall.

How conditioners control the epicuticles

So to make this frizzy, tangled hair play nice, conditioner’s main purpose is to get the epicuticle flakes to lay down as smoothly as possible. To start, a small amount of acid in the conditioner will break up some of the charge between each separated flake, helping them fall against each other more tightly. These are followed up by a series of lubricating ingredients that essentially coat each hair in a temporary sheath of protective oil. Ingredients like quaternary ammonium salts are attracted to the negatively-charged keratins in the epicuticle, followed by fatty alcohols like cetyl alcohol a handful of silicones to round things out. These silicones not only cap off the protective matrix of fatty molecules, but also add a fair amount of shine, as if each hair was laminated in vitamin E-infused plastic. This may sound like a lot of chemistry on your head, which it is, but it’s not really anything all that exotic or worrisome. If you’ve ever made your own salad dressing or mayonnaise, you could probably handle whipping up a batch of conditioner in your own kitchen.

So what about the aforementioned vitamin E? Or any other cool, fancy or compelling ingredients that your hair products might contain? There’s a good chance that they’re their for your nose and imagination more than your hair. Since the keratin in your hair isn’t alive, coating it with oily, fatty ingredients is really the best that you can aim for. Beyond that, ingredients that give a conditioner a nice smell, color and texture in your hand is all optional. Products that promise ‘intense deep conditioning’ or other impressive claims probably can’t do more than an application of coconut oil. For smooth, shiny hair, it’s really just a matter of getting just the right amount of grease to keep your epicuticles in line.

Bonus: So what’s shampoo doing?

Ignoring all the scents and gimmicks packed into each bottle, shampoos essentially work like any other soap out there. They’re full of “surfacant” molecules that have one hydrophillic end and one lipophillic end. As you scrub your head, the Lipophillic end of these molecules grabs dirt, oils and fats off your hair. When you rinse, the hydrophillic ends grab the passing water molecules, only to be pulled off your head and down the drain. They take the dirt and oil with them in the process, leaving your hair clean and… ready to be re-oiled by your conditioner.

Source: How does hair conditioner work? by Krystnell A. Storr , Science Line

On August 6th, 2018 we learned about

Specific levels of light pollution matter to nocturnal predatory insects

I admit that sometimes we leave our porch light later than we need to. It somehow seems friendlier to our neighbors to share a little light with the folks on our street, and only a few moths ever seem to get confused or distracted by the glow of the single bulb near our door. Of course, since we’re not the only family on the street to do this, the cumulative effect can be much greater than what we notice on our porch— scientists have been finding that humanity’s propensity to shine a light anywhere and everywhere is causing a lot of problems for animals that evolved to live under the darkness of night. The effects of light pollution aren’t always easily predictable, with some species behavior shifting dramatically depending on the exact amount of light they’re lit by.

Brighter isn’t better

While we usually associate porch lights with moths alone, half of all insect species are nocturnal, so there’s a lot of possible outcomes from growing levels of light pollution. Parasitoid wasps like Aphidius megourae, for instance, like to hunt other insects like aphids in the low light of the evening. Researchers found that the wasps actually benefited from just a small amount of light pollution, such as from a town just over the horizon. Since most humans would like to keep the plants that aphids like to eat for ourselves, this may seem like an upside to light pollution.

When light levels increased, however, the tables turned in the aphids’ favor. Brighter conditions made the wasps confused and distracted, making them incredibly ineffective hunters. This left the aphid populations unchecked, and exposed the wasps to risk of hunger and attack from other predators.

Spare some darkness for nocturnal species

Researchers worry that this relationship is just one of many possible problems faced by nocturnal insects around the world. More and more of the planet’s landmasses are being lit at night, and this is very likely stressing various ecosystems that sun-loving humans aren’t likely to notice until real problems develop. Insect populations are declining, which is quickly leading to issues with pollination and food sources of larger animals. As much as people prefer well-lit spaces, we should consider at least holding ourselves to the dim light of a nightlight if we want to help preserve these nighttime ecosystems.

Source: Night-time lighting changes how species interact by University of Exeter, Phys.org

On July 24th, 2018 we learned about

Like humans, tree shrews’ taste buds make spicy peppers palatable

Chile peppers are great, if you don’t mind the whole “sensation of pain” thing. By activating the TRPV1 receptor in an animal’s mouth, the capsaicin in the peppers “burns” and scares off most of the creatures that would otherwise enjoy munching on a colorful, crunchy source of vitamin C. Other animals, like birds with diminished TRPV1 receptors, can just eat chiles without knowing what they’re missing. The real weirdos in all this are the mammals that do experience that harmless bit of pain and then actively seek out more of it. While many humans certainly fall into this last category, the more surprising chile lovers were recently realized to be Chinese tree shrews.

Eating more peppers with less pain

Tree shrews (Tupaia belangeri chinensis) don’t normally eat chile peppers, so it’s a bit odd that this connection was ever uncovered. It started when researchers planning to use the shrews in medical experiments were looking for the animals’ preferred foods, apparently “stumbling” upon the fact that the rat-sized mammals would eat a pepper without the slightest hint of discomfort. In fact, when given the option of corn snacks with or without spicy infusions, the shrews actually preferred hotter blends over blander options. This was in direct contrast mice in the same facility who notably recoiled from any food with spicy capsaicinoids in it.

Aside from the shrews’ overall interest in eating peppers, this gap in the two critters’ reactions wasn’t completely surprising. Despite their name, these tree shrews aren’t rodents, being more closely related to primates like us than to mice, which is why they were of interest to the laboratory in the first place. That said, the real difference in how each animal experienced capsaicin came down to only a single amino acid missing from the shrews’ TRPV1 receptors, making it slightly more difficult for the spice-triggering molecule to do its job. Essentially, the shrews could still taste the spiciness, but just less of it per bite.

Partnering with a spicy plant

Of course, this would be of little use if the shrews never needed to eat something spicy. Without peppers in their natural diet, it’s assumed that the shrews evolved their taste for capsaicin by eating Piper boehmeriaefolium. These plants also produce capsaicinoids, and the shrews may be the only creature evolved to eat them. This has essentially forced the two organisms into a partnership, where the shrews have access to a food source nobody else has the tongue to tackle, while the plants rely on the shrews to scatter their seeds. It’s unclear if this leads to the enjoyment capsaicin-loving humans get from eating spicy food, but the shrews did show a preference for foods that burn like their favorite P. boehmeriaefolium plants they grew up with.

Source: Hot Take: Tree Shrews Love Chili Peppers by Mindy Weisberger, Live Science

On July 24th, 2018 we learned about

The Andromeda galaxy’s past and future growth is fueled by collisions with its cosmic kin

The Earth is currently flying around the Sun at around 70,000 miles-per-hour. The Sun is dragging our solar system through the Milky Way galaxy at around 450,000 miles-per-hour. The Milky Way, though composed of 150 to 250 billion different stars, is moving through a cluster of galaxies known as the Local Group at around 250,000 miles-per-hour. While there’s enough open space in space to allow our solar system room to maneuver, it seems like massive galaxies flying around would likely lead to some kind of collision. As it turns out, intuition is actually correct in this case, as researchers have calculated that nearby galaxies have recently crashed into each other in the not too distant past, and more collisions are expected in the future.

Andromeda’s acquisitions

The largest galaxy in the Local Group is Andromeda, which is estimated to be home to around a trillion stars. It wasn’t always that big though, as astronomers believe it has a long history of colliding with, and consuming, smaller galaxies in its path. Two billion years ago, it likely gobbled up what would have been the third-largest galaxy in the Local Group, the blandly-named M32 galaxy. Based on the age of the stars M32 stars still clustered together in Andromeda, researchers believe this collision was substantial. The jump in Andromeda’s celestial population was probably 20 times greater than any acquisitions in the past.

The simulations that lead to those figures match up well with other research teams’ observations, who also determined that Andromeda experienced a major collision between 1.8 and 3 billion years ago. The one major surprise in all this is how these collisions haven’t reshaped Andromeda more dramatically. Researchers expected that sucking up so many new stars would force Andromeda to adopt a smoother oval shape, but somehow the galaxy has retained a spiral, suggesting we don’t fully understand how these shapes are formed.

Milky Way Merger

If any humans are still around in four billion years, we may be able to find out more about that process from front row seats here on Earth. Andromeda’s next acquisition has been calculated to be our very own Milky Way galaxy. The Milky Way is the second-largest galaxy in the local group, and also a spiral galaxy, so the merger of these two massive galaxies should be quite impressive. As far as we know, it would be the largest restructuring the Milky Way has ever experienced, and will take around two billion years to complete.

If you have a distant relative still on this planet somehow, they’ll have plenty to watch, but not directly experience. The night sky will start to fill with stars from Andromeda’s core, and new stars will start popping up as various forms of mass merge together. Our solar system probably won’t be subject to any violent collisions though, instead being pushed towards the outer edge of the resulting “Milkomeda” galaxy. Granted, our own Sun will likely prevent this from being much of a concern as it should be expanding into an Earth-consuming red giant in the middle of all this, but at least the view from our solar system’s gas giants will be impressive.

Source: The Milky Way Had a Big Sibling Long Ago — And Andromeda Ate It by Mike Wall, Space.com

On July 23rd, 2018 we learned about

Echolocating bats squeak softer when they’re flying in stealth mode

One of the best things a nocturnal animal can do to hide its location is to stay quiet. For example, the cats soft feet and owls’ fringed feathers allow these predators to approach their prey in near silence, keeping their approach hidden for as long as possible. Of course this strategy is a lot to expect from bats though, as echolocating species depend on making sound to not only find their prey, but navigate around obstacles in the dark as well. Nonetheless, difficult doesn’t mean impossible, as some bats have been found to purposely reduce their sound “footprint” in order to better mask their locations.

Modulating volume to trick moths

Barbastelle bats (Barbastella barbastellus) like to hunt a variety of insects, including tiger moths. After generations of being eaten by bats, these moths have evolved hearing ranges that let them detect and even interfere with bats’ echolocation calls, making it harder for the bats to surprise their targeted prey. To compensate, barbastelle bats have learned to turn down the volume on their echolocation squeaks as they approach a moth. To figure out exactly how much effort the bats put into this strategy, researchers attached a microphone over a bait-moth in the forest, allowing them to record exactly what prey would hear as a bat attacks.

Since the relative loudness of sound greatly increases with distance, the bats have to be very careful in how they modulate their voices. To keep the moths in the dark concerning the bat’s approach, the bats lower the volume of each squeak just the right amount to make the sound stay consistent to the listening moth. So the moth can certainly hear the bat’s echolocation, but it won’t sound like it’s getting any closer. The bat isn’t hiding its presence, but it does hide its location well enough to get the drop on its prey.

Navigating without being noticed

Hiding an attack on a moth is one thing, but what about bats that want to hide from other bats? This is apparently a concern of hoary bats (Lasiurus cinereus) migrating for mating season, who want to go and find potential mates without attracting unwanted conflict from rival suitors. Obviously, these bats are quite well attuned to the sound of their own species, which is probably why the bats revert to navigating with what researchers are calling ‘micro-calls.’

These super-soft squeaks are three orders of magnitude quieter than most echolocation, making the bats’ voices nearly inaudible. The catch is that these quiet bats are also nearly flying blind, as their echolocation is only able to report on their immediate surroundings. In an experiment, mist nets were set up on a bat migration routes in norther California, and the bats only seemed to notice the nets at the last second. Despite a few full-strength squeaks to assist with evasive maneuvers, many of the bats still collided with the net, indicating that flying in “stealth mode” carries a degree of risk for the incognito bat.

Conservation concerns

While there hopefully aren’t too many nets set up on the bats’ migration routes, there are wind turbines. The bats relying on micro-calls are much less likely to avoid the spinning blades of the turbines, thanks to their reduced range of “visibility.” They’re also less likely to be detected by conservationists, who have generally relied on the sound of full-throated echolocation to determine where to build turbines in the first place. Knowing that those checks may have missed these very quiet bats will hopefully shape future conservation studies, possibly driving the adoption of alternate methods of bat detection. Just don’t tell the moths about it.

Source: Bats go quiet during fall mating season by Wake Forest University, Phys.org

On July 23rd, 2018 we learned about

The invention of trapeze, and the tights that went with it

“Maybe someone needed a better way to swing in the branches of a tree?”

That’s probably not a concern most people worry about, but then again, it’s hard to tie something like a trapeze to any practical purpose. Even after a week at circus camp, my nine-year-old was clearly stretching to figure out what could have inspired the design of such a simple but specific device.

“They didn’t have airplanes then, so was part of a blimp?”

To be fair, the origin story of the trapeze isn’t necessarily intuitive. A young man named Jules, who had grown up learning to climb and tumble in his father’s gymnasium, saw ropes hanging over the accompanying swimming pool. He placed a cross bar between two ropes, supposedly to use as a chin-up bar. Apparently it didn’t take long for other uses of a swinging bar to be found, because within a year this acrobat had put together a performance in his home town of Toulouse, France.

Within three years of that first performance in 1856, Jules had not only moved past his would-be career as a lawyer to work in the Cirque Napoleon in Paris, but he had a second act figured out as well. On November 12th, he swung from one trapeze to another for the first time, gripping audiences’ attention as never before. While the swimming pool was traded for a set of mattresses, more trapezes were added to the performance, allowing Jules to do back-to-back somersaults between five different swings.

“Was his name Mr. Trapeze?”

No- the name trapeze probably came from the Latin trapezium, referring to an “irregular quadrilateral,” like a trapezoid. That’s not to say that young Jules’ name was really forgotten though, since his last name was Leotard.

To safely swing and climb among the ropes and bars of his trapezes, Jules Leotard created a form-fitting body suit out of wool. While it was probably quite hot to wear, the elastic nature of wool allowed him to move without being hindered or snagged on any equipment. It also helped Mr. Leotard hold the attention of many audience members, as the tight outfit revealed his physique in a way unheard of at the time. The combined spectacle of the trapeze and costuming helped make Leotard quite successful, earning him plenty of money and notoriety, including the song the “The Daring Young Man On The Flying Trapeze.”

Leotard’s body suit wasn’t referred to as a ‘leotard’ until around ten years after he died in 1870. As eye-popping as the garment was when it was first created, it’s now fairly standard for athletes and dancers around the world. That’s not to say that Jule’s first passion has died out though- as recently as 2013, performer Han Ho Song performed five consecutive somersaults off a trapeze in Stuttgart, Germany. The key difference is that he updated Leotard’s trick from 1859, making all five revolutions in a single jump.

Source: Trapeze origins, Vertical Wise

On July 19th, 2018 we learned about

Even with extra atmospheric carbon dioxide, plant-eating dinosaurs probably didn’t struggle with nutritional deficiencies

If a mouthful of meat has more calories than the same volume of veggies, how could the world’s biggest dinosaurs manage as herbivores? Between having relatively small mouths and a diet we presume to be based around green, leafy material, it’s hard to imagine how a 33-ton Apatosaurus could find time to do anything but eat in order to power its enormous body. To further complicate things, scientists have long believed that the higher concentration of carbon dioxide (CO2) in the Mesozoic atmosphere would have encouraged plant growth but left them with less nutritional value. Unless these animals had some amazing metabolic trick unheard of in any of their living bird and reptile relatives, the simplest explanation would be for some of these assumptions to be… wrong.

Approximating the Mesozoic atmosphere

As one of the key building blocks of plant life on Earth, CO2 availability does make a difference in how plants grow. Since it’s hard to pull nutritional data from fossilized wood or leaf impressions, scientists conducted an experiment, growing various plants in different atmospheric conditions. The plants were all picked as approximations of the species that lived millions of years ago, and included things like dawn redwoods, monkey puzzle conifers, ginkgo, ferns and horsetails. Naturally, these plants have likely changed to adapt to modern conditions on Earth in the last 65 – 250 million years, but they could hopefully offer a sense of how CO2 would affect their nutrient levels.

Growing a tree or fern in 400 to 2,000 parts per million concentrations of CO2 is only step one though. To figure out how much one of these high-carbon plants might benefit a hungry dinosaur, researchers had to next come up with a fake digestive tract, which they created by fermenting the plants in cattle rumen fluid for 72 hours. By capturing the various byproducts of this process, this technique is used to figure out how easily digestible food is for livestock, and thus could give us a sense of how easy or tough any particular plant was to extract nutrients from. Chewing and other processing strategies like gastroliths weren’t really included in the ‘simulation,’ although since different species of dinosaur ate differently, that seems like a fair omission.

Everything a growing dinosaur needs

In the end, researchers found that the extra CO2 didn’t reduce the nutritional value of these plants as much as had been previously assumed. A 33-ton sauropod was calculated to have only needed 242 pounds of monkey puzzle leaves grown in the CO2-rich Triassic air. That’s certainly a lot of food, but since it’s at the low-end for an African elephant’s daily intake, it would have certainly been possible. If that weren’t good news enough for large herbivores, researchers also found that some plants showed no loss of nutrition at all. A dinosaur eating horsetails grown at three-times modern CO2 levels would only need 112 pounds of food a day, assuming they really liked horsetails.

The overall takeaway is that herbivorous dinosaurs likely had a more nutritious salad bar than we’d ever thought. The gap between these nutrition values and earlier estimates suggest that ancient flora could have fed 20 percent more herbivores than anyone thought, possibly requiring reconsideration of dinosaur population density in general. As exciting as more giant sauropods and hadrosaurs may sound, not every animal would have benefited from these CO2-soaked leaves. Herbivorous insects rely a lot on nitrogen in the plants they eat, which was one of the few nutrients that was definitely reduced in the experimental plants. It’s too early to say at this point, but it’s possible that insect populations suffered in the way we had previously assumed dinosaurs did.

Source: The real palaeo diet: the nutritional value of dinosaur food by Susannah Lydon, The Guardian

On July 19th, 2018 we learned about

Without climate control, heat waves take a measurable toll on our cognitive abilities

On the hottest days of summer, I generally just feel like giving up. By later afternoon, temperatures in my older building easily surpass whatever’s happening outside, a factor compounded by the outdated myth that “nobody needs an air conditioner in northern California.” The net effect is a feeling of tired fogginess, making concentration on just about any task rather difficult. While this may sound like a lot of whining (it is!) scientists have actually been able to quantify the cognitive hit inflicted by seasonal spikes in heat, pointing out that they take a measurable toll on all of us.

Testing the effects of living in high temperatures

Unusually high temperatures associated with heat waves have long been known to be detrimental to human health, although most research on heat has focused on cases when it’s literally a danger to people’s lives. To investigate cognitive issues possibly experienced by everyone, researchers purposely skipped at-risk populations like infants and the elderly, working only with healthy college students. In theory, any issue that would affect a 22-year-old would probably be an issue for 30- and 40-year-olds as well. The only other criteria that mattered was whether or not each student had air-conditioning in the dormitory where they lived.

Every day of the study, test participants were asked to take a few cognitive tests when they woke up in the morning. The tests included tasks like quickly reading the names of colors with letters displayed in conflicting hues, which is a long-standing way to asses how well someone can filter relevant information in a hurry. They were also asked to do some math and memory tests, giving researchers a range of performance metrics to compare. To make sure environmental conditions were also comparable, test subjects’ rooms were outfitted with temperature, carbon dioxide, humidity and noise sensors. Physical activity and sleep were also tracked with a wearable device.

Extra time and additional errors

After five days of normal temperatures, there was a spike in the area’s heat index. Almost immediately, students living without air conditioning started showing a decrease in cognitive performance. They took 13.4 percent longer in deciphering the color words, and also had 13.3 percent more errors in their math tests. Even after the heatwave broke and the outside world returned to normal, much of that heat was retained indoors, extending the impact of overheated students’ low scores.

Anyone who has lived through unusually hot days won’t be surprised by this, but anecdotally hot homes don’t help science diagnose health problems shape policy. By measuring the significant impact heat has one people’s ability to handle cognitive tasks, this study reveals that rising global temperatures may be causing more immediate and widespread problems than people realized. It’s practical to demand air conditioning for every hot home on the planet, but we may need to further prioritize heat-shedding designs in future construction, plus look for ways to mitigate possible problems caused by people too hot to think clearly.

Source: Extreme heat and reduced cognitive performance in adults in non-air-conditioned buildings by Harvard T.H. Chan School of Public Health, Medical Xpress