5 things we didn’t put on our 2024 list of 10 Breakthrough Technologies

No one can predict the future, but  here at MIT Technology Review we spend much of our time thinking about what it might hold. One thing we know is that it’s especially hard to make predictions about technology. Most emerging technologies fizzle or flame out. Some start out as consumer devices but wind up finding their niche in more specialized applications. Only a few become household names. 

Each year, we put together a list of 10 Breakthrough Technologies, picking the advances that we think have the greatest potential to change our lives (for better or worse). We’ve done this for more than 20 years, and next month we’ll reveal our picks for the 2024 list. 

We haven’t always been right (RIP, Baxter), but we’ve often been early to spot important areas of progress (we put natural-language processing on our very first list in 2001; today this technology underpins large language models and generative AI tools like ChatGPT).  

Every year, our reporters and editors nominate technologies that they think deserve a spot, and we spend weeks debating which ones should make the cut. Here are some of the technologies we didn’t pick this time—and why we’ve left them off, for now. 

New drugs for Alzheimer’s disease

Alzmeiher’s patients have long lacked treatment options. Several new drugs have now been proved to slow cognitive decline, albeit modestly, by clearing out harmful plaques in the brain. In July, the FDA approved Leqembi by Eisai and Biogen, and Eli Lilly’s donanemab could soon be next. But the drugs come with serious side effects, including brain swelling and bleeding, which can be fatal in some cases. Plus, they’re hard to administer—patients receive doses via an IV and must receive regular MRIs to check for brain swelling. These drawbacks gave us pause. 

Sustainable aviation fuel 

Alternative jet fuels made from cooking oil, leftover animal fats, or agricultural waste could reduce emissions from flying. They have been in development for years, and scientists are making steady progress, with several recent demonstration flights. But production and use will need to ramp up significantly for these fuels to make a meaningful climate impact. While they do look promising, there wasn’t a key moment or “breakthrough” that merited a spot for sustainable aviation fuels on this year’s list.  

Solar geoengineering

One way to counteract global warming could be to release particles into the stratosphere that reflect the sun’s energy and cool the planet. That idea is highly controversial within the scientific community, but a few researchers and companies have begun exploring whether it’s possible by launching a series of small-scale high-flying tests. One such launch prompted Mexico to ban solar geoengineering experiments earlier this year. It’s not really clear where geoengineering will go from here or whether these early efforts will stall out. Amid that uncertainty, we decided to hold off for now. 

Male-male reproduction

In March, scientists announced that they had created healthy mouse pups by taking cells from two male mice and transforming some of those cells into eggs. The proof-of-concept study shows that this technique can enable reproduction between animals of the same sex, and possibly even allow animals to reproduce without a partner. The advance may someday allow same-sex reproduction in other animals, too—perhaps even humans. But testing something in mice is a long way from testing it in people, so we deferred. 

Over-the-counter Narcan

In March, the US FDA approved the first over-the-counter use of naloxone nasal spray, which reverses opioid overdoses. The spray is now sold by retailers nationwide, including CVS, Walgreens, and Walmart, where two doses cost about $45. Making this medicine more widely available without a prescription will undoubtedly save lives, given that opioid overdoses kill more than 80,000 Americans a year. But the real advance here, in our view, was a new distribution method rather than a scientific or technological breakthrough. 

So what did make our list? Well, you’ll have to come back in January to see. However, we did share one of our 2024 picks in advance with attendees at our recent EmTech MIT event in Cambridge, Massachusetts. Subscribers can watch a video of that special announcement. (Not a subscriber? Get access here.)

Users are doling out justice on a Chinese food delivery app

There are no jury trials in Chinese courts—but if you think the noodles you just got delivered were too hot, a jury of your peers will quickly determine guilt in the app where you ordered it. 

Jury trials, in fact, are plentiful on Chinese apps—especially Meituan, the country’s most popular food delivery service, where millions of users have volunteered to arbitrate complaints between customers and restaurants. Offering it as a way for restaurants to appeal bad reviews they believe are unreasonable, Meituan crowdsources help from users by showing them the review, details of the order, and supplementary notes from the restaurant. Then users can vote on whether to take down the review from the restaurant’s public page.

The vast majority of cases are trivial: the steamed rice was too firm, there were not enough utensils, the portion was too small. And then there’s the perennial complaint: the food is always too spicy or not spicy enough. 

For example, a customer left a one-star review for one restaurant, saying that the “medium-spicy river snail rice noodle” ended up being not spicy at all. Yet the order detail showed that the user actually asked for the noodles to be “not spicy.” Bang: 91% of the jury voted that the customer was the guilty party. The review would be removed.

Lately, judging who’s in the wrong in these situations has become a favorite pastime for young Chinese users, who are increasingly sharing particularly ridiculous cases on social media. It’s not all that different from laughing at a ridiculous “Am I the Asshole” post on Reddit and contributing your two cents, except it has been institutionalized by a major tech company as a content moderation mechanism.

While a few other Chinese apps have similar features, Meituan’s is arguably the most popular at the moment. Meituan first introduced this feature in 2020 and called it “Kangaroo Juries,” since the app’s mascot is a yellow kangaroo. But perhaps because that sounded too close to the pejorative term “kangaroo court,” the feature has since been renamed “Little Mei’s Juries.” 

Today, more than 6 million users have participated in “jury duty,” a Meituan spokesperson tells MIT Technology Review, the majority of them college students. (That may sound like a lot of people, but the app’s annual active user base is 677 million people.) Some minor rules have changed since the feature launched, but the essence remains the same: the juries help the platform sift through thousands of petty fights every day and uphold meal-related justice.

The fun of passing judgment

Even though it has existed for a few years, many people have only recently become aware of Meituan’s public jury feature. It’s now frequently a viral topic on social media—and a source of joy for those nosy enough to weigh in on other people’s business.

Yu Mingyao, a college student living in Dalian, first started judging these cases last winter and would occasionally jump into a jury when she was using the app to order food. But she says she didn’t think the feature was really that popular until mid-November, when she screenshotted a few ridiculous cases she had judged, including the spicy rice noodle saga. In another case she posted about, the user gave a restaurant three stars out of five because of a breakup experienced after eating there. The restaurant complained that it wasn’t to blame. 

She posted these on Xiaohongshu, a Chinese social media app, and asked her dozens of followers: “Does anyone have anything funnier to share?”

To her surprise, the post attracted much more attention than she’s ever received. She soon got more than 2,000 comments, many of which were other screenshots of particularly bewildering complaints. People have kept replying to her, and she’s now at the point where she’s getting tired of reading Meituan reviews.

“At least 90% of the [jurors] are doing it for the fun,” Yu says. “If the complaints by the restaurants and the customers were boring, I don’t think there would be many participants.” 

Meituan has clearly designed the feature to require only a light commitment from individual jurors. There are few qualifications needed other than having a verified, active account and passing a “test” that includes judging five simulated complaints. After that, each juror gets a maximum of three cases every 12 hours—meaning it’s more a casual game to keep them in the app than any serious form of crowdsourced platform management. They also don’t get any compensation for their participation, just the mental satisfaction. 

But this doesn’t mean some jurors don’t take their duty very seriously. In one case that was posted on social media, a bubble tea vendor argued that contrary to the complaint, it did place a straw in the delivery package. But some jurors realized that the time stamp in the security camera footage uploaded by the merchant didn’t match the time of the delivery. The restaurant had seemingly fabricated evidence, and in the end, 51% of the jurors sided with the customer.

Meituan encourages the activity of these more serious jurors. In an October announcement, the app said it would reward 20 “quality jury comments” with a gift bag of Meituan merchandise every month. To explain who qualifies, the app offered an example of a juror not just casting a vote, but going above and beyond by consulting catering professionals on pricing standards. 

Weeding out fake or unfair feedback

The public jury function can improve efficiency in resolving disputes and bring more transparency to the platform’s decision-making process, says Angela Zhang, a law professor at the University of Hong Kong, who has done extensive research on what she calls “crowd-judging” features. “Since these decisions are crowdsourced, they align more closely with community norms, helping platforms better understand and integrate these standards,” Zhang says.

Most of the cases up for trial are initiated by the merchants, according to reposted screenshots and Yu’s personal experience. Though the Meituan spokesperson says a user can open a case in some specific situations, for example if they have an issue after they’ve purchased one of the app’s coupons. “I think the main target of this feature is to reduce the number of malicious [customer] reviews,” Yu says. 

The juries may even help uncover reviews that are fraudulent. Food delivery vendors, like any online service, rely heavily on reviews to attract potential customers, which has inspired a black market in both fake five-star reviews for themselves and one-star complaints for competitors.

Chen, a fast-food restaurant owner in Fujian province who has operated a store for more than a year, says that it’s important to retain 4.7 stars out of 5.0. “If it’s lower than [that], you don’t get any traffic, and you can’t make any money,” Chen says. (She asked to be identified by only her last name in order to speak more freely.)

But in practice, it’s not that easy for the merchants to utilize the public jury feature. Chen has had a lot of frustrating experiences with bad reviews, and she says Meituan requires multiple rounds of appeals and attempts to dial up a customer representative to actually open a jury trial. 

In August, Chen received a review that claimed the delivery was missing one portion of rice, and she responded that the rice was merely buried under other food. After failing several times to get the platform to remove this review, she finally got the case to a jury. Twenty-two jurors voted for her, and nine voted for the customer.

“I just have one humble request: whenever a vendor provides enough supporting evidence, a trial by Little Mei’s Juries can be opened,” she says.

A wave of democratic experiments 

Meituan is not the only Chinese consumer tech company that has invited users to weigh in on conflicts. Idle Fish, a secondhand marketplace operated by Alibaba, has a similar “court” system where any dispute between buyers and sellers can be decided by a panel made up of 17 volunteer jurors. Douyin, the Chinese version of TikTok, also allows users to become jurors and help the platform screen out content that violates its rules. 

Like Reddit’s downvote system or X’s community notes, these features let the users participate in enforcing platform policies. But at the same time, some users complain that these features are designed to offload the responsibilities of the platform. 

There have been similar user-governance experiments in the past, but they didn’t last long. WeChat once had a system in which volunteers could decide whether articles had been plagiarized, and Weibo also recruited volunteer content moderators who could suspend other users. 

“Operating a crowd-judging platform isn’t free,” Zhang says. In particular, it takes human resources to maintain the platform. And if it doesn’t attract enough user participation, the system won’t be efficient. Still, Zhang believes that having such a system in place is good for the users and the platform: “Essentially, platforms are delegating some of their authority to their users, creating a more collaborative and democratic governance structure.”

In some cases, the activity of these juries can have pretty serious consequences. The example with the largest scale and highest stakes was probably Xianghubao, a discontinued online mutual-aid product from Alibaba that tried to challenge commercial health insurance in China. 

The idea was that millions of users would each pitch in a few bucks so that when one of them got sick, the pool of money would be used to pay their medical bills. But first, to decide whether a medical bill qualified for payment, Xianghubao asked everyone to study the case details and cast a vote. In 2019, the first-ever case was judged by over 250,000 users. The patient was a man in his 40s who fell down a hole, broke his legs, and lost consciousness. The majority eventually decided, on the basis of his previous health history, to deny paying him 100,000 RMB (about $14,000). The service shut down in 2022.

Meituan has chosen a more entertaining approach with its public jury feature. It certainly doesn’t deal with life-or-death situations like Xianghubao, and by centering the arguments between customers and merchants, it carefully avoids the more controversial problems of the food delivery business—namely, the rights of delivery workers. (“A delivery worker can become a juror as a Meituan user. They can also initiate a trial by Little Mei’s Juries as a consumer,” says the Meituan spokesperson.) 

Meituan’s public jury is ultimately more of a light-hearted activity for users who have placed an order and are waiting for it to arrive. Many users who talk about their experiences on social media compare it to a fun and addictive game. In five seconds, they can laugh at some ridiculous user complaints or examples of a delivery that went wrong. Plus, who doesn’t like to feel that you’re doing the right thing and acting in the name of justice?

This viral game in China reinvents hide-and-seek for the digital age

On a late October evening, I found myself hiding in the shadows of a tree in a Hong Kong park. I was on high alert, warily eyeing everyone walking toward me. I was checking my phone every few seconds, watching the locations of dozens of people who were trying to hunt me down.

I wasn’t actually in danger. I was playing a game of hide-and-seek with 40 strangers in a seven-acre park built on the site of the infamous Kowloon Walled City. It wasn’t a typical hide-and-seek game, though, but rather one for the digital age: both the seekers and the hiders chase and evade each other by following their real-time locations on a map on their phones.

The “cat-and-mouse game,” as it’s usually referred to locally, has gone viral in China this year, drawing thousands of people across the country to events every week. It’s a fun combination of a childhood game, in-person networking, the latest location-sharing technology, and meme-worthy experience. When the game first emerged in February, videos of hide-and-seek players who went wild—climbing up trees, hiding in the sewers—got millions of views on social media.

Each contest convenes dozens of people in a predetermined area, often a large city park. All of them then join a group on Amap, a Chinese Google Maps alternative, and share their live location. Among the participants, 90% are designated as “mice” and have five minutes to run and hide. Then the rest, who are “cats,” will go out and hunt down each mouse with the help of the location sharing, as well as a neon wristband that visually separates them from nonparticipants. Once caught, the mice switch teams and join the cats, so the game gets harder and harder for the remaining mice.

@hypnus1127

During a short trip to Hong Kong last month, I joined two cat-and-mouse games in the city. Both of them had about 40 participants and lasted one hour. The first park was larger and had fewer people, meaning it was prime for running and chasing; the second was crowded and smaller, which made it ideal for trying to blend in with passersby.

Being an indoor person, I’m not always a fan of group physical activities, but the two experiences went far beyond my expectations. The addition of location sharing has turned the kids’ game into a more interactive version of Pokémon Go. Trying to remain hidden in the same spot throughout the game was not possible, since the cats could always see where I was; I needed to get more creative in crafting an escape plan. I quickly learned that deception—hiding my glowing bracelet, pretending to be an innocent jogger, and avoiding checking my phone too often—was also essential to being a good mouse. 

Just watching everyone’s locations in the app was an intense experience. Dozens of little avatars were floating around in the park at once, with cats gradually outnumbering mice as the game progressed. Delays and bugs were plenty, but that added to the fun and difficulty of the game. I could feel safe at one moment, seeing there were no cats around, and panic seconds later when a cat suddenly moved hundreds of feet toward me, likely because its location sharing had lagged. 

As a first-timer, I did okay. For my first game, I survived as a mouse until the last few minutes, when mostly everyone else had converted to the cat side. For my second outing, I converted mid-game and caught two mice myself.

I’ll readily admit some people were much better than I was. Hong Shizhe, a 19-year-old college student, was crowned the “cat king” of the second game, having caught 11 mice by the end. “I like that you can both exercise and have fun in this activity,” Hong says. He first learned about the game through videos people shared on Chinese social media, and he has been to several games in Hong Kong and mainland China since. He told me the largest one had more than 140 participants. Once, he even took his dog to the park with him and still won the game. 

His secret for success? A lot of lies and politics: “You can make a deal with the mice and have them help you find other little mice. You can also pretend to be a mouse and strike up a chat with them.”

Half the fellow players Hong has met in his games are students, the other half young professionals. Like Ultimate Frisbee and a few other social activities that previously became popular in China, cat-and-mouse games are considered a great way for young people to meet each other and make new friends. At my two games in Hong Kong, I heard many participants chatting before the game started, many of whom were new to the city and eager to meet people.

But organizing the game has also become a business. Some games, like the second one I went to, charge participants a small fee (usually less than $10). That second game was hosted by a local group that organizes weekly activities, like camping trips, board games, and barbecue parties.

Transforming an ordinary map app

Many cat-and-mouse games use Amap, which is owned by Alibaba. Since Google services are blocked in China, and there aren’t as many Apple users, Amap is one of the most popular domestic map apps, with over 100 million active users every day.

Amap has enabled real-time location sharing within small groups since at least 2017, and it has in recent years expanded the maximum size of the group to 100 people. This feature has previously been advertised for users like family members tracking each other’s location or hikers keeping tabs on each other in the wild. 

Perhaps inspired by the overwhelming success of Pokémon Go, Amap has done some experiments with gaming too. It has worked with a few Chinese game studios, as well as Alibaba’s e-commerce platforms, to develop games that integrate live location tracking, whether individually or in a group setting. None of these games, however, have caught on. The turn of events this year seems to have been more of an accident: cat-and-mouse was first played on WeChat, but players gradually moved on to Amap on their own and have basically made it the default app choice.

Amap declined to have anyone interviewed for this story, but the company is aware of its sudden popularity. Since September, the app has introduced a few features that cater to players’ needs. Now, users can specifically choose to start a “cat-and-mouse game group” right in the app and create groups over the typical 100-person limit; it can even randomly assign the roles of mice and cats. It also allows users to set customized rules and automates some of the formerly manual processes, like changing mice avatars to cats once players are caught.

All of these are nice-to-have features, but maybe not essential. At least for the two games that I went to, the organizers only used the most basic feature of group location sharing. Some didn’t even know the app had group features in the first place. (This may partly be because of where we were; Google Maps is much more popular in Hong Kong than other apps and only allows location sharing between two people.) 

While it took a little time for the organizers to catch everyone up on how to use Amap and check that they had the right settings, the app is so easy to use that the whole group, including me, soon got the hang of it. 

For a while, I was awed, reflecting that I never expected to be playing games in an app that guides people through their daily commutes. But soon enough, I had no time to think about that. A cat was approaching, and I needed to run for my life.