Self-Control Is Just Empathy With Your Future Self

The same part of the brain that allows us to step into the shoes of others also helps us restrain ourselves.

The Atlantic | Ed Yong

You’ve likely seen the video before: a stream of kids, confronted with a single, alluring marshmallow. If they can resist eating it for 15 minutes, they’ll get two. Some do. Others cave almost immediately.  

 

This “Marshmallow Test,” first conducted in the 1960s, perfectly illustrates the ongoing war between impulsivity and self-control. The kids have to tamp down their immediate desires and focus on long-term goals—an ability that correlates with their later health, wealth, and academic success, and that is supposedly controlled by the front part of the brain. But a new study by Alexander Soutschek at the University of Zurich suggests that self-control is also influenced by another brain region—and one that casts this ability in a different light.

Press your right index finger to the top of your right ear, where it meets your head. Now move up an inch and back an inch. You’re now pointing at your right temporoparietal junction (rTPJ). This area has long been linked to empathy and selflessness. But Soutschek, by using magnetic fields to briefly shut down the rTPJ, has shown that it’s also involved in self-control.

Which makes perfect sense. Empathy depends on your ability to overcome your own perspective, appreciate someone else’s, and step into their shoes. Self-control is essentially the same skill, except that those other shoes belong to your future self—a removed and hypothetical entity who might as well be a different person. So think of self-control as a kind of temporal selflessness. It’s Present You taking a hit to help out Future You.

“For a long time, people have speculated that we use the same mechanisms to reason about other people as about our hypothetical selves,” says Rebecca Saxe from MIT. “So this new study fits really well.”

Saxe should know. She was one of the first scientists to link the rTPJ to theory of mind—the ability to understand the mental states of other people. In 2005, she and Nancy Kanwisher scanned people’s brains while they listened to stories in which protagonists made poor choices based on false beliefs. This experiment showed that the TPJ is active specifically when people are “reasoning about the contents of another person’s minds”—the essence of theory of mind. This region, the duo wrote, helps people to think about thinking people.

At the same time, many other neuroscientists were doing similar experiments and getting the same answers. The consensus was striking, Saxe later wrote. “Because there was almost no pre-existing neuroscience of theory of mind, researchers came to the topic with unusually few preconceptions about where to look in the brain. In those circumstances, neuroimaging is notoriously fickle, producing many false positives and false negatives. Yet every group that sought to identify brain regions implicated in ToM got essentially the same answer; and in study after study, we still do.”

Many other studies have since expanded on those early results. If the rTPJ is bigger, people are more likely to behave altruistically. If the neurons within it are better-connected (and well-linked to other parts of the brain), people show less bias towards their own in-groups. If the area is stimulated by electric currents, people become better at taking someone else’s perspective.

And if the region is disrupted, it changes our ability to reason about morality. Consider a woman who poisons her friend’s coffee—if she does so deliberately, we’d judge her more harshly than if she acted accidentally. Intent matters, and we need the rTPJ to judge intent. When Liane Young, one of Saxe’s former students, disrupted the rTPJ using magnetic fields, she found that people were more lenient towards the deliberate poisoner, as long as her friend survived. With their ability to gauge intent disrupted, they started looking to outcomes instead.

Not everything fits with the idea of the rTPJ as a nexus for theory of mind. For example, many studies suggest that it affects our ability to shift our attention from one part of space to another, like a technician moving a spotlight around. “Even in my own small lab, people disagree about the function of the rTPJ,” says Young, now a professor at Boston College.

If you look at the debate and relax your eyes, you can probably merge the two viewpoints into one. Maybe the rTPJ is a region that redirects our attention from one thing to another—whether between objects in the world around us, or between our minds and other people’s. Alternatively, it’s likely that what we call the rTPJ is not actually a singular bit of the brain. “There’s a lot of work suggesting that there are different sub-regions—one of which does spatial reorienting, and the other does perspective-taking,” says Young.

That’s where Soutschek’s study comes in. He specifically focused on the back half of the rTPJ—the one that’s been more heavily linked to empathy—and disrupted it in 43 volunteers. When that happened, the recruits became more likely to pocket a pile of cash for themselves rather than splitting it with a partner, and especially when the partner was a stranger. But they were also more likely to pick a small immediate lump of cash over a larger future one, especially when the delays were long.

A second experiment explained why. This time, the volunteers saw a picture of a man standing in a room with red discs on the wall. The volunteers could see all the discs, but they had to say how many the man in the room could see. They had to shift their perspective to his, and they became worse at that when their rTPJ was disrupted. What’s more, Soutschek showed that the extent of their bias—their inability to leave their own heads—predicted both how impulsive and how selfish they were in the earlier experiment.

This tells us that impulsivity and selfishness are just two halves of the same coin, as are their opposites restraint and empathy. Perhaps this is why people who show dark traits like psychopathy and sadism score low on empathy but high on impulsivity. Perhaps it’s why impulsivity correlates with slips among recovering addicts, while empathy correlates with longer bouts of abstinence. These qualities represent our successes and failures at escaping our own egocentric bubbles, and understanding the lives of others—even when those others wear our own older faces.

Ed Yong is a staff writer at The Atlantic, where he covers science. 

From Fish to Humans, A Microplastic Invasion May Be Taking a Toll

Tiny bits of plastic have seeped into soil, fish and air, posing a threat to animal and human health.

Scientific American | Andrea Thompson

Photo by Niccoló Pontigia / EyeEm / Getty Images.

Mark Browne had a suspicion. He hoped the samples of dried blood taken from a blue mussel and placed under a special microscope would tell him if he was correct. As a fuzzy, three-dimensional image of the mussel’s blood cells appeared, there they were, right in the middle—tiny specks of plastic.

Whereas photos of sea turtles eating plastic bags have become the poster child of the environmental harm wrought by humanity’s plastic waste, research like Browne’s illustrates the scope of the problem is far larger than the trash we can see. Tiny pieces of degraded plastic, synthetic fibers and plastic beads, collectively called microplastics, have turned up in every corner of the planet—from Florida beach sands to Arctic sea ice, from farm fields to urban air.

Their size—from about five millimeters, or the size of a grain of rice, down to microscopic—means they can be ingested by a wide range of creatures, from the plankton that form the basis of the marine food chain to humans. As Browne’s 2008 study was one of the first to demonstrate, those plastic particles don’t always pass harmlessly through the body. The finding “was one of those sort of bittersweet moments,” the ecotoxicologist at the University of New South Wales in Sydney says. “You’re pleased that some prediction you’ve made has come true—but then you’re devastated” because of the potentially profound ecological implications.

Ingested microplastic particles can physically damage organs and leach hazardous chemicals—from the hormone-disrupting bisphenol A (BPA) to pesticides—that can compromise immune function and stymie growth and reproduction. Both microplastics and these chemicals may accumulate up the food chain, potentially impacting whole ecosystems, including the health of soils in which we grow our food. Microplastics in the water we drink and the air we breathe can also hit humans directly.

Browne is one of dozens of scientists trying to sort out exactly what this widespread, motley assortment of microplastics pollution might be doing to animals and ecosystems. Tantalizing evidence is emerging, from the impaired reproduction of fish to altered soil microbe communities. As researchers accumulate more data, “we start realizing we’re just at the tip of the iceberg with the problem,” Browne says.

A Threat to Organs and Bloodstream

When Browne experimented with blue mussels back in 2008, many researchers thought animals would just excrete any microplastics they ate, like “unnatural fiber,” as Browne called it—but he wasn’t so sure. He tested the idea by placing mussels in water tanks spiked with fluorescent-tagged microplastic particles smaller than a human red blood cell, then moved them into clean water. For six weeks he harvested the shellfish to see if they had cleared the microplastics. “We actually ran out of mussels,” Browne says. The particles “were still in them at the end of those trials.”

The mere presence of microplastics in fish, earthworms and other species is unsettling, but the real harm is done if microplastics linger—especially if they move out of the gut and into the bloodstream and other organs. Scientists including Browne have observed signs of physical damage, such as inflammation, caused by particles jabbing and rubbing against organ walls. Researchers have also found signs ingested microplastics can leach hazardous chemicals, both those added to polymers during production and environmental pollutants like pesticides that are attracted to the surface of plastic, leading to health effects such as liver damage. Marco Vighi, an ecotoxicologist at the IMDEA Water Institute in Spain, is one of several researchers running tests to see what types of pollutants different polymers pick up and whether they are released into the freshwater and terrestrial animals that eat them. The amount of microplastics in lakes and soils could rival the more than 15 trillion tons of particles thought to be floating in the ocean’s surface alone.

What matters most is whether these physical and chemical impacts ultimately affect an organism’s growth, reproduction or susceptibility to illness. In a surprising study published in March 2018, not only did fish exposed to microplastics reproduce less but their offspring, who weren’t directly exposed to plastic particles, also had fewer young, suggesting the effects can linger into subsequent generations. Some organisms such as freshwater crustaceans called amphipods haven’t yet exhibited any ill effects, perhaps because they can handle natural indigestible material like bits of rock, says Martin Wagner, an ecotoxicologist at Norwegian University of Science and Technology, who studied them. And some species have shown toxic effects from microplastics exposure from certain types of plastic, but not others, says Chelsea Rochman, a microplastics researcher at the University of Toronto.

Most work on microplastic impacts has been done in the lab for short stints, with only a single type of plastic, often with larger particles than some species tend to eat, and at higher concentrations than are found in the environment. The studies “won’t tell us about long-term ecological consequences happening at low concentrations,” Wagner says. He is one of several researchers starting to bridge that gap by matching animals to the polymers and pollutants they are most likely to encounter and incorporating the intricacies of the real world where microplastics “won’t be the only stressor,” Wagner says. Microplastics could be a last straw for species subject to pressures as chemical pollutants, overfishing and climate change. “It’s just damn complicated,” Wagner says.

Inviting Chaos

Messy, real-world conditions are the goal on the green lawn of a botanical garden in Frankfurt, Germany. A row of small, identical ponds stretch across the grass, exposed to the elements. Wagner spiked each one with different microplastic particles—some virgin polymers, some contaminated with pollutants—to see how freshwater insects and zooplankton fare. Although Wagner hasn’t yet observed any overt impacts, he is investigating whether certain organisms exhibit more subtle signs of harm, which could have a ripple effect throughout an ecosystem’s food web.

Such cascading impacts could happen even when individual species don’t seem to suffer. Browne’s mussels showed no short-term ill effects but he worries their accumulated microplastics could be transferred to animals that eat them. “They might not be so kind to the other organisms,” he says.

Like Wagner, Browne is venturing farther out into the real world. He has several freezers’ worth of fish and other organisms plucked from Sydney Harbor that he will examine for ingested microplastics. His team will be linking those to the routes by which microplastics might be entering the harbor and looking for signs of ecological damage such as changes in population size. The approach means animals can behave normally and are exposed to typical environmental conditions such tides and storms, as well as a host of other stressors such as changing ocean temperatures and industrial pollutants. “We want a chaotic system because if something can cause an impact in that chaotic system, above those other stresses, we know that we really, really need to be worried about it,” Browne says.

Matthias Rillig, a plant ecologist at Free University of Berlin, has shown how microplastics can affect organisms by altering their environments. In a study he co-authored, soil laden with polyester microfibers was much fluffier, retained more moisture and seemed to affect the activity of microbes that are crucial to the soil nutrient cycle. The finding is an early but concerning one, given that farmers around the world apply microfiber-rich treated sewage sludge as fertilizer to agricultural land. Rillig is also one of several scientists looking to see how microfibers in soils might be affecting crop growth.

Full Circle

Microplastics may threaten people more directly. A study published in April 2018 found particles and microfibers in packaged sea salt, beer, bottled water and tap water, making it virtually certain we are ingesting microplastics. In bottled beverages microplastics could be infiltrating during the bottling process; microfibers could be falling from the atmosphere into the reservoirs that supply tap water. Even for researchers steeped in the field, “it still comes as a shock,” Rochman says. “It just shows that the mismanagement of our waste is coming back to us.”

Because it is unethical to intentionally feed doses of microplastic particles to humans, some researchers, like Browne, have turned to medical studies that use particles to deliver precise amounts of drugs to specific areas of the body to get a better sense of how easily microplastics might move through humans. If particles are small enough, they might migrate through the body and potentially accumulate in places like the bloodstream. A study of hamsters injected with microplastics suggests such particles can lead to blood clots.

Humans could also be inhaling microfibers as they fall from the sky—everywhere from the heart of Paris to the remote Arctic. Small airborne particles are known to lodge deep in the lungs where they can cause various diseases, including cancer. Factory workers who handle nylon and polyester have shown evidence of lung irritation and reduced capacity (although not cancer), but they are exposed to much higher levels than the average person. Stephanie Wright, a research associate at King’s College London, is trying to better understand how much microfiber humans are actually exposed to and whether airborne microplastics might penetrate the lungs. She is also teaming up with the university’s toxicology unit to examine their lung tissue collection for signs of microfibers and related damage.

Some scientists say the focus on microplastics in humans might be missing a larger point: People are continually exposed to plastic food and beverage containers, which could be a much bigger source of at least the chemicals added to plastics such as the endocrine disruptor BPA. The potential exposure to microplastics hasn’t stopped Rochman from eating seafood, however. “To the best of my knowledge the benefits outweigh the costs,” she says. It could be that, as with many pollutants, there is a threshold beyond which microplastics become toxic to humans or other species. “We just need to try to understand what that threshold is,” she notes.

Experts say the sheer ubiquity of the contaminant combined with the harm that has already been observed is enough for humanity to start to clean up its act. “There are always questions to be answered,” Rochman says, but we have reached the point where “it’s enough information to act toward solutions.”

Andrea Thompson, an associate editor at Scientific American, covers sustainability.