Learn why helping others feels like helping ourselves, how wild animals eat healthy, and how the Sahara feeds the Amazon. We're less likely to remember the things we've given to friends than strangers by Kelsey Donk We’re Worse At Remembering Exactly What We’ve Given To Friends Than What We’ve Given To Strangers. (2021, April 12). Research Digest. https://digest.bps.org.uk/2021/04/12/were-worse-at-remembering-exactly-what-weve-given-to-friends-than-what-weve-given-to-strangers/ Uğurlar, P., Posten, A.-C., & Zürn, M. (2021). Interpersonal closeness impairs decision memory. Social Psychology, 52(2), 125–129. https://doi.org/10.1027/1864-9335/a000439 How do wild animals eat a healthy diet when humans struggle to? by Ashley Hamer (Listener question from Jason in Port Ewen, New York) Predators hunt for a balanced diet. (2012). ScienceDaily. https://www.sciencedaily.com/releases/2012/01/120110192942.htm Provenza, F. (2018, November 30). Animals Can Help Us Rediscover Our Nutritional Wisdom. Scientific American Blog Network. https://blogs.scientificamerican.com/observations/animals-can-help-us-rediscover-our-nutritional-wisdom/ Strauss, S. (2006). Clara M. Davis and the wisdom of letting children choose their own diets. Canadian Medical Association Journal, 175(10), 1199–1199. https://doi.org/10.1503/cmaj.060990 Schatzker, M. (2015, April 9). How Flavor Drives Nutrition. WSJ; The Wall Street Journal. https://www.wsj.com/articles/how-flavor-drives-nutrition-1428596326 Tucker, A. (2009, July 14). Why Modern Foods Hijack Our Brains. Smithsonian Magazine; Smithsonian Magazine. https://www.smithsonianmag.com/arts-culture/why-modern-foods-hijack-our-brains-63123747/ Deckersbach, T., Das, S. K., Urban, L. E., Salinardi, T., Batra, P., Rodman, A. M., Arulpragasam, A. R., Dougherty, D. D., & Roberts, S. B. (2014). Pilot randomized trial demonstrating reversal of obesity-related abnormalities in reward system responsivity to food cues with a behavioral intervention. Nutrition & Diabetes, 4(9), e129–e129. https://doi.org/10.1038/nutd.2014.26 The Amazon Rainforest feeds on millions of tons of dust from the Sahara Desert per year by Grant Currin Saharan Dust Feeds Amazon’s Plants. (2011). NASA. https://www.nasa.gov/content/goddard/nasa-satellite-reveals-how-much-saharan-dust-feeds-amazon-s-plants Yu, H., Chin, M., Yuan, T., Bian, H., Remer, L. A., Prospero, J. M., Omar, A., Winker, D., Yang, Y., Zhang, Y., Zhang, Z., & Zhao, C. (2015). The fertilizing role of African dust in the Amazon rainforest: A first multiyear assessment based on data from Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations. Geophysical Research Letters, 42(6), 1984–1991. https://doi.org/10.1002/2015gl063040 Follow Curiosity Daily on your favorite podcast app to learn something new every day withCody Gough andAshley Hamer — for free!
Learn why helping others feels like helping ourselves, how wild animals eat healthy, and how the Sahara feeds the Amazon.
We're less likely to remember the things we've given to friends than strangers by Kelsey Donk
How do wild animals eat a healthy diet when humans struggle to? by Ashley Hamer (Listener question from Jason in Port Ewen, New York)
The Amazon Rainforest feeds on millions of tons of dust from the Sahara Desert per year by Grant Currin
Follow Curiosity Daily on your favorite podcast app to learn something new every day with Cody Gough and Ashley Hamer — for free!
Find episode transcript here: https://curiosity-daily-4e53644e.simplecast.com/episodes/how-do-wild-animals-know-what-to-eat
CODY: Hi! You’re about to get smarter in just a few minutes with Curiosity Daily from curiosity-dot-com. I’m Cody Gough.
ASHLEY: And I’m Ashley Hamer. Today, you’ll learn about why we’re less likely to remember things we’ve given to friends than strangers; and why the Amazon Rainforest feeds on millions of tons of dust from the Sahara Desert. We’ll also answer a listener question about how wild animals know how to eat a healthy diet.
CODY: Let’s satisfy some curiosity.
When’s the last time you helped a friend? If you can’t remember, that doesn’t necessarily mean you’re a bad friend. New research suggests that we're less likely to remember the things we've given to friends than strangers — and that forgetfulness actually says good things about our friendship.
This paper comes from researchers at the University of Cologne in Germany, who find that the closer we are to friends, the worse our memory is for how much we’ve given them.
So we might end up doing more for our close friends than we would for acquaintances. And sure, that seems pretty intuitive. But the research suggests it’s about more than just our love of our friends. Our brains may actually blur the boundaries between ourselves and our BFFs. Helping them may feel more like helping ourselves.
For the studies, researchers had people play something called the Trust Game. They gave people some amount of a theoretical resource, like pizza or bitcoin, and asked how much they’d give to another hypothetical player. The assumption was that that player would give some portion back to them later.
In the first study, people named the person they were closest to and played the Trust Game, imagining that it was with that person. Afterward, players had to recall how much of each resource they had given in all eight rounds of the game. People who saw themselves as most separate from others in a previous survey had better memories of how much they’d given away.
In the next studies, researchers asked people to give resources to either their best friend or someone they’d only met once. They found that people had significantly worse memories of how much they’d shared with their closest friends than with strangers.
Previous studies have indicated that our personal boundaries become fuzzy in close relationships, but this study suggests that being close to people could actually make our memories of our decisions worse.
But don’t be alarmed: the researchers say this could actually be a good thing. Giving resources away is costly. When we give away time, food, or… bitcoin… to other people, we lose those things for ourselves. But if the line between the self and others is blurred, it could be easier for people to give things away. Selfless gifts to people in our communities have a positive impact on those communities — and by extension, on ourselves. So don’t fear your fuzzy friend memory. It’s a good thing!
We got a voicemail from Jason in Port Ewen, New York. Jason was listening to the ursinology episode of Ologies (heyyy!) when he heard the guest mention that bears only eat certain parts of the salmon in order to get them fatter for hibernation. And that inspired a question for us!
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First of all, it’s true that animals do seem to know what to eat to stay healthy. Studies have shown that when you give a variety of foods to an animal — whether they’re wild or domesticated — they tend to eat them in a combination that provides the best nutritional profile. And back in the 1920s, a pediatrician named Clara Marie Davis actually tried this same experiment with newly weaned infants: she gave them a choice of 33 different types of foods and let them decide which ones to eat. They ended up choosing the combination of foods that left them well nourished and healthy at the end of the several-year study.
So how do animals and babies know something that adult humans seem to struggle with? According to Fred Provenza, a professor of behavioral ecology at the University of Utah, it comes down to taste. The flavors of different foods tell animals things about their nutrition, and their bodies ensure they get what they need by craving different flavors at different times. The same may have been going on with the infants in that 1920s study — but the key in both of these cases is that all the foods available are what most would consider healthy.
So why can’t adult humans trust our tastes? According to Provenza, two things have happened over time to mess with this flavor-feedback system: one is that commercially available foods have been designed to hijack that system and make their flavors irresistible. The other is that commercial agriculture has bred fruits and vegetables to make them grow bigger and bruise less in shipment, without as much focus on flavor. As a result, fruits and vegetables taste worse and worse as so-called junk food tastes better and better.
The good news is that you can retrain your brain to crave healthy food! In a 2014 study, Tufts University researchers put people on a healthy diet for six months, then scanned their brains. In the end, the reward centers of their brains showed more sensitivity to healthy, low-calorie foods than a control group that hadn’t changed their diets. It’s possible! You just need to surround yourself with healthy food — and stay away from the drive-through. Thanks for your question, Jason! If you have a question, send us an email or a voice recording to curiosity at discovery dot com, or leave us a voicemail like Jason did at 312-596-5208.
How does rainfall in the Sahara desert affect plant life in the Amazon? The answer: a whole lot, actually. It's a good reminder that Earth is full of surprising connections.
In this case, it’s all about dust. You might be surprised to hear that wind carries a massive amount of stuff from the Sahara Desert in northern Africa across the Atlantic Ocean and over the Caribbean and South America. Researchers are using satellites designed to spy on clouds and airborne particles to learn more about this brownish superhighway in the sky.
This is a lot of dust. According to research from 2015, winds pick up more than 180 million tons of it from the Sahara each year. If humans wanted to move that much dust, they’d have to use nearly 700,000 semi-trucks.
Dust is not the most glamorous of substances, but this dust is sort of special. That’s because a lot of it comes from an ancient lakebed in Chad, called the Bodélé Depression. We call this stuff dust, but it’s really billions upon billions of dead microorganisms that lived in the lake long ago. Their mineralized little bodies are chock full of phosphorus. As any gardening enthusiast knows, phosphorus is an important nutrient that plants need to flourish. And as it happens, phosphorus is in short supply in the Amazon because rain washes away tons and tons of it every year.
Not all of the dust that leaves the Sahara makes it to the Amazon, though. Satellite data shows that about 50 million tons falls into the Atlantic on its way over. Some of it overshoots the Amazon, and some of it heads in a different direction altogether. In the end, an average of about 30 million tons makes the complete trip from the world’s largest desert to the world’s largest tropical rainforest. That’s about 100,000 semi-trucks’ worth.
Now, that’s an average. The researchers behind the 2015 study found a lot of variation from year to year. They aren’t sure what causes the change, but there was a strong correlation between the amount of dust moving through the atmosphere one year and the amount of rain that had fallen the year before in the Sahel, a long stretch of semi-arid land that sits just below the Sahara.
Researchers have a lot to learn about this tremendous transfer of matter across the Earth’s surface, but one thing’s for sure: this planet isn’t a simple place, and nothing exists on its own.
CODY: Before we recap what we learned today, here’s a sneak peek at what you’ll hear next week on Curiosity Daily.
ASHLEY: Next week, you’ll learn about how stress can make a pregnant person twice as likely to have a girl;
Why invasive species aren’t always harmful;
How scientists are making better solar panels using human hair;
The surprising emotional benefits of resolving an argument;
And more! Okay, so now, let’s recap what we learned today.
[ad lib optional]
ASHLEY: Today’s writers were Kelsey Donk and Grant Currin.
CODY: Our managing editor is Ashley Hamer, who was also a writer on today’s episode.
ASHLEY: Our producer and audio editor is Cody Gough.
CODY: Have a great weekend! Join us again Monday to learn something new in just a few minutes, as we pass before your ears on Curiosity Daily
ASHLEY: And until then, stay curious!