We often attribute financial problems to bad life decisions: Why didn’t that person stay in college? Why didn’t they pick a more lucrative career? Why did they have so many kids? But several recent studies suggest that having less money can actually affect thinking and memory for the worse. In the most recent of these papers, scientists found a link between being lower on the socioeconomic ladder and changes in the brain.

For this study, published this week in the Proceedings of the National Academy of Sciences, researchers at the Center for Vital Longevity at the University of Texas at Dallas scanned the brains of 304 people aged 20 to 89. The researchers were looking for two things: first, how much gray matter the subjects had in their brains; second, how their brain networks were organized. In the brain, areas that have related functions often show similar activity: The areas that control speech, for example, tend to interact more with each other and less with the areas involved in different bodily functions. It’s generally considered to be a good thing for brain networks to be “segregated” in this way.

1. The Aristocracy Is Dead …

For about a week every year in my childhood, I was a member of one of America’s fading aristocracies. Sometimes around Christmas, more often on the Fourth of July, my family would take up residence at one of my grandparents’ country clubs in Chicago, Palm Beach, or Asheville, North Carolina. The breakfast buffets were magnificent, and Grandfather was a jovial host, always ready with a familiar story, rarely missing an opportunity for gentle instruction on proper club etiquette. At the age of 11 or 12, I gathered from him, between his puffs of cigar smoke, that we owed our weeks of plenty to Great-Grandfather, Colonel Robert W. Stewart, a Rough Rider with Teddy Roosevelt who made his fortune as the chairman of Standard Oil of Indiana in the 1920s. I was also given to understand that, for reasons traceable to some ancient and incomprehensible dispute, the Rockefellers were the mortal enemies of our clan.

Every afternoon around 4:00 p.m., when school lets out, Brandon, an 18-year-old high-school senior in Los Angeles who asked to be referred to only by his first name, goes “Bird hunting.” He heads for his minivan and, on the drive home, he’ll swing through convenient neighborhoods, picking up about 13 Bird electric scooters along the way, tossing them into the back of his car.

“I have a whole system,” he says. “I’ll go home, put the 13 I initially caught on the chargers. They’ll charge for about three hours until around 7 or 8 p.m.”—when Bird makes more scooters available for charger pickup. “Then I’ll go back out.”

Over the course of the next few hours, Brandon loops around his Santa Monica, California, neighborhood collecting as many scooters as possible. He brings back his bounty and, as his parents sleep, neatly sets them up to charge in batches overnight.

Three years ago, at a conference on transatlantic issues, the subject of artificial intelligence appeared on the agenda. I was on the verge of skipping that session—it lay outside my usual concerns—but the beginning of the presentation held me in my seat.

The speaker described the workings of a computer program that would soon challenge international champions in the game Go. I was amazed that a computer could master Go, which is more complex than chess. In it, each player deploys 180 or 181 pieces (depending on which color he or she chooses), placed alternately on an initially empty board; victory goes to the side that, by making better strategic decisions, immobilizes his or her opponent by more effectively controlling territory.

Artificial intelligence owes a lot of its smarts to Judea Pearl. In the 1980s he led efforts that allowed machines to reason probabilistically. Now he’s one of the field’s sharpest critics. In his latest book, The Book of Why: The New Science of Cause and Effect, he argues that artificial intelligence has been handicapped by an incomplete understanding of what intelligence really is.

Three decades ago, a prime challenge in artificial-intelligence research was to program machines to associate a potential cause to a set of observable conditions. Pearl figured out how to do that using a scheme called Bayesian networks. Bayesian networks made it practical for machines to say that, given a patient who returned from Africa with a fever and body aches, the most likely explanation was malaria. In 2011 Pearl won the Turing Award, computer science’s highest honor, in large part for this work.

Americans of high-school age are 82 times more likely to die from a gun homicide than 15- to 19-year-olds in the rest of the developed world.

This stark discrepancy is often treated as a baffling fact, requiring some counterintuitive explanation. After today’s massacre in Texas, the state’s lieutenant governor, Dan Patrick, suggested that the problem may be that high schools have too many doors. “Had there been one single entrance possibly for every student, maybe [the shooter] would have been stopped.”

At other moments, we’re told that the problem is that we need to do a better job guessing which troubled teens may prove murderous at some point in the future, or dealing with the excesses of masculinity, or possibly the crisis of meaning and identity in the secularizing modern world. As always, though, there is a simpler and more powerful explanation of why there has been no similar school shooting in Germany since 2009; or in Canada since 2016; none in the United Kingdom since 1996—while conversely, more young Americans have died in school shootings in 2018 than in all the nation’s combat operations all over the world.*  

What exactly do the North Koreans mean when they say they’re willing to denuclearize? And how exactly would they do so? These are the key mysteries at the heart of the upcoming Trump-Kim summit—and indeed they threatened to derail the whole thing this week when Kim Jong Un objected to National-Security Adviser John Bolton’s vision for it. In a statement attributed to Vice Foreign Minister Kim Kye Gwan, North Korea chastised Bolton for his invocation of the “Libya model” of unilateral denuclearization as a template, noting that the “world knows too well that our country is neither Libya nor Iraq which have met miserable [fates].” The White House quickly walked back Bolton’s remarks.

The exchange did little to clarify how the U.S. plans to achieve denuclearization. But for a group of former U.S. government officials who have been meeting with North Korean officials over the past decade, North Korea’s own plans are anything but hidden. A series of meetings with North Korean officials in 2013, which I attended along with other former U.S. officials, holds valuable clues—and they show that the North Koreans have given a great deal of thought to denuclearization and almost certainly have a concrete plan of action for the upcoming summit, whether the White House does or not.  

There are two Staceys angling to become Georgia’s first woman governor.

One Stacey—Stacey Abrams—is black. She’s the former minority leader of the state House of Representatives. The other, Stacey Evans, is white. She founded her own law firm and has represented the state’s 42nd district since 2011. Both Democrats have years of experience in the state House, and each has pledged to advance an ambitious, progressive agenda for Georgia. But their approaches have been markedly different. Abrams has structured her campaign around minority empowerment and outreach through a targeted, grassroots-style campaign. Evans, meanwhile, with a promise to Bring Hope Back to Georgia, has sold herself as the candidate who can court independents and swing voters, a self-proclaimed “champion for common sense.”

Every week for the second season of Westworld, three Atlantic staffers will discuss new episodes of HBO’s cerebral sci-fi drama.

According to the authoritative Freedom House rankings, we have seen over a decade of deterioration in free institutions. Outright massacre is the order of the day in countries from Burma to the Levant, and tyrants no less cunning than Mussolini or Franco subvert the rule of law, freedom of the press, and freedom of speech from Warsaw to Ankara, and from Beijing to Moscow. As was the case 80 years ago, many in the United States would rather step back from a world that seems turbulent but not their problem. Their president wants tariffs and walls, while polls show that for many Americans, democracy, freedom of speech, and freedom of the press are not values to be defended to the death. Against this backdrop, a new exhibit at the United States Holocaust Memorial Museum—“Americans and the Holocaust”—seems to speak to where America stands today, even though it has been years in the making and thus was not designed as a political commentary on the United States of 2018.