Chapter 5 The Four Foundational Harms Social Deprivation, Sleep Deprivation, Attention Fragmentation, and Addiction

Chapter 5

The Four Foundational Harms: Social Deprivation, Sleep Deprivation, Attention Fragmentation, and Addiction

One morning, on a family trip to Vermont in 2016, my six-year-old daughter was playing a video game on my iPad. She called out to me: “Daddy, can you take the iPad away from me? I’m trying to take my eyes off it but I can’t.” My daughter was in the grip of a variable-ratio reinforcement schedule administered by the game designers, which is the most powerful way to take control of an animal’s behavior short of implanting electrodes in its brain.

In 1911, in one of the foundational experiments in psychology, Edward Thorndike put hungry cats into “puzzle boxes.” These were small cages from which the cat could escape and get food if it performed a particular behavior, such as pulling on a ring connected to a chain that opened the latch. The cats thrashed around unhappily, trying to escape, and they hit on the solution eventually. But what do you think happened the next time the same cat was put into that same box? Did it go right for the ring? No. Thorndike found that the cats thrashed around again, although on average they hit upon the solution a bit faster the second time, and a bit faster each time after that, until they performed the escape behavior immediately. There was always a learning curve. There was never a moment of insight in which the cat “got it” and the times suddenly dropped.

Thorndike described the cat’s learning like this: “The one impulse, out of many accidental ones, which leads to pleasure, becomes strengthened and stamped in.” He said that animal learning is “the wearing smooth of a path in the brain, not the decisions of a rational consciousness.” [1] Keep that phrase in mind whenever you see anyone (including yourself) making repetitive motions on a touch screen, as if in a trance: “the wearing smooth of a path in the brain.”

My goal in part 3 is to examine the evidence of harm from the Great Rewiring across a wide spectrum of outcomes. The rapid switch from flip phones (and other basic phones) to smartphones with high-speed internet and social media apps created the new phone-based childhood, which laid down many new paths in the brains of Gen Z. In this chapter, I describe the four foundational harms of the new phone-based childhood that damage boys and girls of all ages: social deprivation, sleep deprivation, attention fragmentation, and addiction. Then, in chapter 6, I’ll lay out the main reasons why social media has been especially damaging to girls, including chronic social comparison and relational aggression. In chapter 7, I’ll examine what’s going wrong for boys, whose mental health did not decline as suddenly as it did for girls, but who have been withdrawing from the real world and investing ever more of their efforts in the virtual world for several decades. In chapter 8, I’ll show that the Great Rewiring encouraged habits that are exactly contrary to the accumulated wisdom of the world’s religious and philosophical traditions. I’ll show how we can draw on ancient spiritual practices for guidance on how to live in our confusing, overwhelming time. But first, I need to explain what the phone-based childhood is and where it came from.

The Arrival of the Phone-Based Childhood

When Steve Jobs announced the first iPhone in June 2007, he described it as “a widescreen iPod with touch controls, a revolutionary mobile phone, and breakthrough internet communication device.” [2] The first iteration of the iPhone was quite simple by today’s standards, and I have no reason to believe it was harmful to mental health. I bought one in 2008 and found it to be a remarkable digital Swiss Army knife, full of tools I could call on when I needed them. It even had a flashlight! It was not designed to be addictive or to monopolize my attention.

This soon changed with the introduction of software development kits, which allowed third-party apps to be downloaded onto mobile devices. This revolutionary move culminated in the launch of the App Store by Apple in July 2008, starting with 500 apps available. Google followed suit with the Android Market in October 2008, which was rebranded and expanded into Google Play in 2012. By September 2008, the Apple App Store had grown to hold more than 3,000 apps, and by 2013 it had more than 1 million. [3] The Google Play store grew right alongside Apple, reaching 1 million apps in 2013. [4]

The opening of smartphones to third-party apps led to fierce competition among companies large and small to create the most engaging mobile apps. The winners of this race were often those that adopted free-to-use, advertising-based business models because few consumers would pay $2.99 for an app if a competitor offered one for free. This proliferation of advertising-driven apps caused a change in the nature of time spent using a smartphone. By the early 2010s, our phones had transformed from Swiss Army knives, which we pulled out when we needed a tool, to platforms upon which companies competed to see who could hold on to eyeballs the longest. [5]

The people with the least willpower and the greatest vulnerability to manipulation were, of course, children and adolescents, whose frontal cortices were still highly underdeveloped. Children have been drawn powerfully to screens since the advent of television, but they could not take those screens with them to school or when they went outside to play. Before the iPhone, there was a limit to the amount of screen time a child could have, so there was still time for play and face-to-face conversation. But the explosion of smartphone-based apps such as Instagram in the exact years in which teens and preteens were moving from basic phones to smartphones marked a qualitative change in the nature of childhood. By 2015, more than 70% of American teens carried a touch screen around with them, [6] and these screens became much better at holding their attention, even when they were with their friends. This is why I date the beginning of the phone-based childhood to the early 2010s.

As I noted in the introduction, I use the term “phone-based” in an expansive sense to include all internet-connected devices . In the late 2000s and early 2010s, many of these devices, particularly video game consoles such as the PS3 and Xbox 360, gained access to the internet, introducing advertising and new commercial incentives to platforms that had once been self-enclosed. Insofar as laptops with high-speed internet provided access to social media platforms, internet-based computer games, and free streaming platforms with user-generated videos (including YouTube and many online pornography sites), they are part of the phone-based childhood too. I use the term “childhood” here expansively as well, to include both childhood and adolescence.

Social Media and Its Transformations

Social media has evolved over time, [7] but there are at least four major features common to the platforms we generally think of as being clear examples of social media: user profiles (users can create individual profiles where they can share personal information and interests); user-generated content (users create and share a variety of content to a broad audience, including text posts, photos, videos, and links); networking (users can connect with other users by following their profiles, becoming friends, or joining the same groups); and interactivity (users interact with each other and with the content they share; interactions may include liking, commenting, sharing, or direct messaging). The prototypical social media platforms such as Facebook, Instagram, Twitter, Snapchat, TikTok, Reddit, and LinkedIn share all four features, as does YouTube (even though YouTube is more widely used as the world’s video library than for its social features) and also the now popular video game streaming platform Twitch. Even modern adult-content sites, like OnlyFans, have adopted these four features. On the other hand, messaging apps such as WhatsApp and Facebook Messenger do not have all four features, and while they are certainly social, they would not be considered social media.

A transformational shift in the nature of social media happened in the years around 2010 that made it more harmful to young people. In the early years of Facebook, Myspace, and Friendster (all founded between 2002 and 2004), we called these services social networking systems because they were primarily about connecting individuals, such as long-lost high school friends or fans of a particular musician. But around 2010 there was a series of innovations that fundamentally changed these services.

First and foremost, in 2009, Facebook introduced the “like” button and Twitter introduced the “retweet” button. Both of these innovations were then widely copied by other platforms, making viral content dissemination possible. These innovations quantified the success of every post and incentivized users to craft each post for maximum spread, which sometimes meant making more extreme statements or expressing more anger and disgust. [8] At the same time, Facebook began using algorithmically curated news feeds, which motivated other platforms to join the race and curate content that would most successfully hook users. Push notifications were released in 2009, pinging users with notifications throughout the day. The app store brought new advertising-driven platforms to smartphones. Front-facing cameras (2010) made it easier to take photos and videos of oneself, and the rapid spread of high-speed internet (reaching 61% of American homes by January 2010 [9] ) made it easier for everyone to consume everything quickly.

By the early 2010s, social “networking” systems that had been structured (for the most part) to connect people turned into social media “platforms” redesigned (for the most part) in such a way that they encouraged one-to-many public performances in search of validation, not just from friends but from strangers. Even users who don’t actively post are affected by the incentive structures these apps have designed. [10]

These changes explain why the Great Rewiring began around 2010 and why it was largely complete by 2015. Children and adolescents, who were increasingly kept at home and isolated by the national mania for overprotection, found it ever easier to turn to their growing collection of internet-enabled devices, and those devices offered ever more attractive and varied rewards. The play-based childhood was over; the phone-based childhood had begun.

The Opportunity Cost of a Phone-Based Childhood

Suppose a salesman in an electronics store told you he had a new product for your 11-year-old daughter that would be very entertaining—even more than television—with no harmful side effects of any kind, but also no more than minimal benefits beyond the entertainment value. How much would this product be worth to you?

You can’t answer this question without knowing the opportunity cost . Economists define that term as the loss of other potential gains when one alternative is chosen. Suppose you are starting a business and you consider paying $2,000 to take a course on graphic design at a local university so that you can make your company’s communications look better. You can’t just ask yourself whether more attractive flyers and websites will earn back the $2,000. You have to consider all the other things you could have done with that money—and, perhaps more importantly, what else you could have done to help your business with all the time you spent taking the course.

So, when that salesman tells you that the product is free, you ask about the opportunity cost. How much time does the average child spend using the product? Around 40 hours a week for preteens like your daughter, he says. For teens aged 13 to 18, it’s closer to 50 hours per week. At that point, wouldn’t you walk out of the store?

Those numbers—six to eight hours per day—are what teens spend on all screen-based leisure activities. [11] Of course, children were already spending a lot of their time watching TV and playing video games before the smartphone and internet became parts of their daily lives. Long-running studies of American adolescents show that the average teen was watching a little less than three hours per day of television in the early 1990s. [12] As most families gained dial-up access to the internet during that decade, followed by high-speed internet in the 2000s, the amount of time spent on internet-based activities increased, while time spent watching TV decreased. Kids also began to spend more time playing video games and less time reading books and magazines. Putting it all together, the Great Rewiring and the dawn of the phone-based childhood seem to have added two to three hours of additional screen-based activity, on average, to a child’s day, compared with life before the smartphone. These numbers vary somewhat by social class (more use in lower-income families than in high-income families), race (more use in Black and Latino families than in white and Asian families [13] ), and sexual minority status (more use among LGBTQ youth; see more detail in this endnote [14] ).

I should note that researchers’ efforts to measure screen time are probably underestimates. When the question is asked differently, Pew Research finds that a third of teens say they are on one of the major social media sites “almost constantly,” [15] and 45% of teens report that they use the internet “almost constantly.” So even if the average teen reports “just” seven hours of leisure screen time per day, if you count all the time that they are actively thinking about social media while multitasking in the real world, you can understand why nearly half of all teens say that they are online almost all the time. That means around 16 hours per day—112 hours per week—in which they are not fully present in whatever is going on around them. This kind of continuous use, often involving two or three screens at the same time, was simply not possible before kids carried touch screens in their pockets. It has enormous implications for cognition, addiction, and the wearing smooth of paths in the brain, especially during the sensitive period of puberty.

In Walden , his 1854 reflection on simple living, Henry David Thoreau wrote, “The cost of a thing is the amount of... life which is required to be exchanged for it, immediately or in the long run.” [16] So what was the opportunity cost to children and adolescents when they started spending six, or eight, or perhaps even 16 hours each day interacting with their devices? Might they have exchanged any parts of life that were necessary for healthy human development?

Harm #1: Social Deprivation

Children need a lot of time to play with each other, face to face, to foster social development. [17] But back in chapter 2, I showed that the percentage of 12th graders who said that they got together with their friends “almost every day” dropped sharply after 2009.

You can see the loss of friend time in finer detail in figure 5.1, from a study on how Americans of all ages spend their time. [18] The figure shows the daily average number of minutes that people in different age brackets spend with their friends. Not surprisingly, the youngest group (ages 15–24) spends more time with friends, compared with the older groups, who are more likely to be employed and married. The difference was very large in the early 2000s, but it was declining, and the decline accelerated after 2013. The data for 2020 was collected after the COVID epidemic arrived, which explains why the lines bend downward in that last year for the two older groups. But for the youngest age group there is no bend at 2019. The decline caused by the first year of COVID restrictions was no bigger than the decline that occurred the year before COVID arrived. In 2020, we began telling everyone to avoid proximity to any person outside their “bubble,” but members of Gen Z began socially distancing themselves as soon as they got their first smartphones.

Daily Time with Friends, by Age Group

Figure 5.1. Daily average time spent with friends in minutes. Only the youngest age group shows a sharp drop before the 2020 data collection, which was performed after COVID restrictions had begun. (Source: American Time Use Study.) [19]

Of course, teens at the time might not have thought they were losing their friends; they thought they were just moving the friendship from real life to Instagram, Snapchat, and online video games. Isn’t that just as good? No. As Jean Twenge has shown, teens who spend more time using social media are more likely to suffer from depression, anxiety, and other disorders, while teens who spend more time with groups of young people (such as playing team sports or participating in religious communities) have better mental health. [20]

It makes sense. Children need face-to-face, synchronous, embodied, physical play. The healthiest play is outdoors and includes occasional physical risk-taking and thrilling adventure. Talking on FaceTime with close friends is good, like an old-fashioned phone call to which a visual channel has been added. In contrast, sitting alone in your bedroom consuming a bottomless feed of other people’s content, or playing endless hours of video games with a shifting cast of friends and strangers, or posting your own content and waiting for other kids (or strangers) to like or comment is so far from what children need that these activities should not be considered healthy new forms of adolescent interaction; they are alternatives that consume so much time that they reduce the amount of time teens spend together.

The sharp drop of time with friends actually underestimates the social deprivation caused by the Great Rewiring because even when teens are within a few feet of their friends, their phone-based childhoods damage the quality of their time together. Smartphones grab our attention so powerfully that if they merely vibrate in our pockets for a tenth of a second, many of us will interrupt a face-to-face conversation, just in case the phone is bringing us an important update. We usually don’t tell the other person to stop talking; we just pull out our phone and spend some time pecking at it, leaving the other person to conclude, reasonably, that she is less important than the latest notification. When a conversation partner pulls out a phone, [21] or when a phone is merely visible [22] (not even your own phone), the quality and intimacy of a social interaction is reduced. As screen-based technologies move out of our pockets and onto our wrists, and into headsets and goggles, our ability to pay full attention to others is likely to deteriorate further.

It’s painful to be ignored, at any age. Just imagine being a teen trying to develop a sense of who you are and where you fit, while everyone you meet tells you, indirectly: You’re not as important as the people on my phone. And now imagine being a young child. A 2014 survey of children ages 6–12, conducted by Highlights magazine, found that 62% of children reported that their parents were “often distracted” when the child tried to talk with them. [23] When they were asked the reasons why their parents were distracted, cell phones were the top response. Parents know that they are shortchanging their own children. A 2020 Pew survey found that 68% of parents said that they sometimes or often feel distracted by their phones when they are spending time with their children. Those numbers were higher for parents who were younger and who were college educated. [24]

The Great Rewiring devastated the social lives of Gen Z by connecting them to everyone in the world and disconnecting them from the people around them. As a Canadian college student wrote to me,

Gen Z are an incredibly isolated group of people. We have shallow friendships and superfluous romantic relationships that are mediated and governed to a large degree by social media.... There is hardly a sense of community on campus and it’s not hard to see. Oftentimes I’ll arrive early to a lecture to find a room of 30+ students sitting together in complete silence, absorbed in their smartphones, afraid to speak and be heard by their peers. This leads to further isolation and a weakening of self identity and confidence, something I know because I’ve experienced it firsthand. [25]

Harm #2: Sleep Deprivation

Parents have long struggled to get their children to go to bed on school nights, and smartphones have exacerbated this struggle. Natural sleep patterns shift during puberty. [26] Teens start to go to bed later, but because their weekday mornings are dictated by school start times, they can’t sleep later. Rather, most teens just get less sleep than their brains and bodies need. This is a shame because sleep is vital for good performance in school and life, particularly during puberty, when the brain is rewiring itself even faster than it did in the years before puberty. Sleep-deprived teens cannot concentrate, focus, or remember as well as teens who get sufficient sleep. [27] Their learning and their grades suffer. [28] Their reaction times, decision making, and motor skills suffer, which elevates their risk of accidents. [29] They are more irritable and anxious throughout the day, so their relationships suffer. If sleep deprivation goes on long enough, other physiological systems become perturbed, leading to weight gain, immune suppression, and other health problems. [30]

Teens need more sleep than adults—at least nine hours a night for preteens and eight hours a night for teens. [31] Back in 2001, a leading sleep expert wrote that “almost all teenagers, as they reach puberty, become walking zombies because they are getting far too little sleep.” [32] When he wrote that, sleep deprivation had been rising for a decade, as you can see in Figure 5.2. Sleep deprivation then leveled off through the early 2010s. After 2013, it resumed its upward march.

Teens Who Get Less Than 7 Hours of Sleep

Figure 5.2. Percent of U.S. students (8th, 10th, and 12th grade) who get less than seven hours of sleep on most nights. (Source: Monitoring the Future.) [33]

Is that just a coincidence, or is there evidence directly linking the upsurge in sleep problems to the arrival of the phone-based childhood? There’s a lot of evidence. A review of 36 correlational studies found significant associations between high social media use and poor sleep, and also between high social media use and poor mental health outcomes. [34] That same review also found that high social media use at one time predicted sleep problems and worse mental health at later times. One experiment found that adolescents who restricted their use of screen devices after 9 p.m. on school nights for two weeks showed increased total sleep time, earlier sleep onset times, and improved performance on a task that required focused attention and quick reactions. [35] Other experiments, using a variety of different screen-based technologies (including e-readers, video games, and computers), have also found that late-night use is disruptive to sleep. [36] Thus, the relationships are not merely correlations; they are causal.

It makes intuitive sense. A study by Jean Twenge and colleagues of a large U.K. data set found that “heavy use of screen media was associated with shorter sleep duration, longer sleep latency, and more mid-sleep awakenings.” [37] The sleep disturbances were greatest for those who were on social media or who were surfing the internet in bed. [38]

It’s not just social media on smartphones that has disturbed sleep for Gen Z; sleep deprivation is increased by the ease of access to other highly stimulating smartphone activities, including mobile gaming and video streaming. [39] As the CEO of Netflix put it on an earnings call with investors when asked about Netflix’s competitors, “You know, think about it, when you watch a show from Netflix and you get addicted to it, you stay up late at night. We’re competing with sleep, on the margin.”? [40]

What does sleep deprivation do to the rapidly changing brains of adolescents? To answer that question, we can turn to the findings of the Adolescent Brain Cognitive Development Study, which scanned the brains of more than 11,000 9- and 10-year-olds back in 2016 and has been following them as they went through puberty and adolescence. Hundreds of academic papers have emerged from this large collaboration, and several examined the effects of sleep deprivation. For example, a 2020 study found that greater sleep disturbance and shorter total sleep time were associated with greater internalizing scores (which include depression), as well as greater externalizing scores (which include aggression and other antisocial actions associated with a lack of impulse control). [41] They also found that the size of the sleep disturbance at the start of the study “significantly predicted depression and internalizing and externalizing scores at 1-year follow-up.” In other words, when your sleep is truncated or disturbed, you’re more likely to become depressed and develop behavioral problems. The effects were larger for girls.

In short, children and adolescents need a lot of sleep to promote healthy brain development and good attention and mood the next day. When screens are allowed in bedrooms, however, many children will use them late into the night—especially if they have a small screen that can be used under the blanket. The screen-related decline of sleep is likely a contributor to the tidal wave of adolescent mental illness that swept across many countries in the early 2010s.

Harm #3: Attention Fragmentation

Kurt Vonnegut’s 1961 short story “Harrison Bergeron” is set in an ultra-egalitarian future America where, by constitutional amendment, nobody is allowed to be smarter, better looking, or more physically able than anyone else. The “handicapper general” is the government officer tasked with enforcing equality of abilities and outcomes. Anyone with a high IQ is required to wear an earpiece at all times that buzzes loudly every 20 seconds or so with a variety of noises designed to interrupt sustained thinking, thereby bringing the person down to the functional intelligence of the average citizen.

I thought about this story as I began to talk with my students a few years ago about how their phones were affecting their productivity. Young people have relied, since the late 1990s, on texting as their basic mode of communication. They keep their ringers off, which means that their phones vibrate repeatedly throughout the day, especially when they participate in group chats. But the situation was far worse than I had imagined. Most of my students get alerts from dozens of apps, including messaging apps (such as WhatsApp), social media apps (Instagram and Twitter), and a variety of news sites that ping them with “breaking news” about politics, sports, and the romantic lives of celebrities. For my MBA students (who are mostly in their late 20s), there are also work-related apps such as Slack. Most of my students also have their phones set to vibrate with an alert every time an email message arrives.

When you add it all up, the average number of notifications on young people’s phones from the top social and communication apps amounts to 192 alerts per day, according to one study. [42] The average teen, who now gets only seven hours of sleep per night, therefore gets about 11 notifications per waking hour, or one every five minutes. And that’s just for the apps that are about communication. When we add in the dozens of other apps for which they have not turned off push notifications, the number of interruptions grows far higher. And we’re still only talking about the average teen. If we zoom in on heavy users, such as older teen girls, who use texting and social media apps far more often than any other group, we are now in the ballpark of one interruption every minute. Thanks to the tech industry and its voracious competition for the limited resource of adolescent attention, many members of Gen Z are now living in Kurt Vonnegut’s dystopia.

In 1890, the great American psychologist William James described attention as “the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought.... It implies withdrawal from some things in order to deal effectively with others.”? [43] Attention is a choice we make to stay on one task, one line of thinking, one mental road, even as attractive off-ramps beckon. When we fail to make that choice and allow ourselves to be frequently sidetracked, we end up in “the confused, dazed, scatterbrained state” that James said is the opposite of attention.

Staying on one road got much harder when the internet arrived and moved much of our reading online. Every hyperlink is an off-ramp, calling us to abandon the choice we made moments earlier. Nicholas Carr, in his aptly titled 2010 book, The Shallows: What the Internet Is Doing to Our Brains , lamented his lost ability to stay on one path. Life on the internet changed how his brain sought out information, even when he was off-line trying to read a book. It reduced his ability to focus and reflect because he now craved a constant stream of stimulation: “Once I was a scuba diver in the sea of words. Now I zip along the surface like a guy on a Jet Ski.”? [44]

Carr’s book was about the internet as he experienced it on his computers in the 1990s and 2000s. He occasionally mentions BlackBerrys and iPhones, which had become popular just a few years before his book was published. But a buzzing smartphone is so much more alluring than a passive hyperlink, so much deadlier for concentration. Every app is an off-ramp; every notification is a Las Vegas–style sign calling out to you to turn the wheel: “Tap here and I’ll tell you what someone just said about you!”

And no matter how hard it is for an adult to stay committed to one mental road, it is far harder for an adolescent, who has an immature frontal cortex and therefore limited ability to say no to off-ramps. James described children like this: “Sensitiveness to immediately exciting sensorial stimuli characterizes the attention of childhood and youth.... the child seem[s] to belong less to himself than to every object which happens to catch his notice.” Overcoming this tendency to flit around is “the first thing which the teacher must overcome.” This is why it is so important that schools go phone-free for the entire school day by using phone lockers or lockable pouches. [45] Capturing the child’s attention with “immediately exciting sensorial stimuli” is the goal of app designers, and they are very good at what they do.

This never-ending stream of interruptions—this constant fragmentation of attention—takes a toll on adolescents’ ability to think and may leave permanent marks in their rapidly reconfiguring brains. Many studies find that students with access to their phones use them in class and pay far less attention to their teachers. [46] People can’t really multitask; all we can do is shift attention back and forth between tasks while wasting a lot of it on each shift. [47]

But even when students don’t check their phones, the mere presence of a phone damages their ability to think. In one study, researchers brought college students into the lab and randomly assigned them to (1) leave their bag and phone out in the entry room of the lab, (2) keep their phone with them in their pocket or bag, or (3) put their phone on their desk next to them. They then had the students complete tasks that tested their fluid intelligence and working memory capacity, such as by solving math problems while also remembering a string of letters. They found that performance was best when phones were left in the other room, and worst when phones were visible, with pocketed phones in between. The effect was bigger for heavy users. The article was titled “Brain Drain: The Mere Presence of One’s Own Smartphone Reduces Available Cognitive Capacity.”? [48]

When adolescents have continuous access to a smartphone at that developmentally sensitive age, it may interfere with their maturing ability to focus. Studies show that adolescents with attention deficit hyperactivity disorder (ADHD) are heavier users of smartphones and video games, and the commonsense assumption is that people with ADHD are more likely to seek out the stimulation of screens and the enhanced focus that can be found in video games. But does causation run in the reverse direction too? Can a phone-based childhood exacerbate existing ADHD symptoms?

It appears so. [49] A Dutch longitudinal study found that young people who engaged in more problematic (addictive) social media use at one measurement time had stronger ADHD symptoms at the next measurement time. [50] Another study by a different group of Dutch researchers used a similar design and also found evidence suggesting that heavy media multitasking caused later attention problems, but they found this causal effect only among younger adolescents (ages 11–13), and it was especially strong for girls. [51]

The brain develops throughout childhood, with an acceleration of change during puberty. One of the main skills that adolescents are expected to develop as they advance through middle school and high school is “executive function,” which refers to the child’s growing ability to make plans and then do the things necessary to execute those plans. Executive function skills are slow to develop because they are based in large part in the frontal cortex, which is the last part of the brain to rewire during puberty. Skills essential for executive function include self-control, focus, and the ability to resist off-ramps. A phone-based childhood is likely to interfere with the development of executive function. [52] I cannot say that light use of these products is harmful to attention, but among heavy users we do consistently find worse outcomes in part because such users are often, to some degree, addicted.

Harm #4: Addiction

When my daughter found herself powerless to lift her eyes up from my iPad, what exactly was going on in her brain? Thorndike didn’t know about neurotransmitters, but he correctly guessed that the repetition of small pleasures played a big role in laying down those new paths in the brain. Now we know that when an action is followed by a good outcome (such as gaining food, or relieving pain, or just achieving a goal), certain brain circuits involved with learning release a bit of dopamine—the neurotransmitter most centrally involved in feelings of pleasure and pain. The release of dopamine feels good; we register it in our consciousness. But it’s not a passive reward that satisfies us and reduces our craving. Rather, dopamine circuits are centrally involved in wanting , as in “that felt great, I want more!” When you eat a potato chip, you get a small hit of dopamine, which is why you then want the second one even more than you wanted the first one.

It’s the same with slot machines: A win feels great, but it doesn’t cause gambling addicts to take their earnings and go home, satisfied. Rather, the pleasure motivates them to keep going. It’s the same for video games, social media, shopping sites, and other apps that routinely cause people to spend far more time or money than they had intended to spend. The neural basis of behavioral addictions to social media or video games is not exactly the same as chemical addictions to cocaine or opiates. [53] Nonetheless, they all involve dopamine, craving, compulsion, and the feeling my daughter expressed—that she was powerless to act on her conscious wishes. That happens by design. The creators of these apps use every trick in the psychologists’ tool kit to hook users as deeply as slot machines hook gamblers. [54]

To be clear, the great majority of adolescents using Instagram or playing Fortnite are not addicted, but their desires are being hacked and their actions manipulated nonetheless. Of course, advertisers have long sought to do exactly this, but touch screens and internet connections opened up vast new possibilities for employing behaviorist techniques, which work best when there are rapid cycles or loops of behaviors and rewards. One researcher who explored these possibilities was B.J. Fogg, a professor at Stanford who wrote a 2002 book titled Persuasive Technology: Using Computers to Change What We Think and Do . Fogg also taught a course titled “Persuasive Technology” in which he taught students how to take behaviorist techniques for training animals and apply them to humans. Many of his students went on to found or work at social media companies, including Mike Krieger, a cofounder of Instagram.

How do habit-forming products hook adolescents? Take the case of a 12-year-old girl sitting at her desk at home, struggling to understand photosynthesis for a test in her science class the next day. How can Instagram lure her away and then keep her away for an hour? App design ers often use a four-step process that creates a self-perpetuating loop, shown in Figure 5.3.

Figure 5.3. The Hooked model. From Nir Eyal’s 2014 book, Hooked: How to Build Habit-Forming Products . In the book, Eyal warned about the ethical implications of misusing the model in a section titled “The Morality of Manipulation.” [55]

The Hooked model guides designers through the loop they need to create if they want to build strong habits in their users.

The loop starts with an external trigger, such as a notification that someone commented on one of her posts. That’s step 1, the off-ramp inviting her to leave the path she was on. It appears on her phone and automatically triggers a desire to perform an action (step 2) that had previously been rewarded: touching the notification to bring up the Instagram app. The action then leads to a pleasurable event, but only sometimes, and this is step 3: a variable reward. Maybe she’ll find some expression of praise or friendship, maybe not.

This is a key discovery of behaviorist psychology: It’s best not to reward a behavior every time the animal does what you want. If you reward an animal on a variable-ratio schedule (such as one time out of every 10 times, on average, but sometimes fewer, sometimes more), you create the strongest and most persistent behavior. When you put a rat into a cage where it has learned to get food by pressing a bar, it gets a surge of dopamine in anticipation of the reward. It runs to the bar and starts pressing. But if the first few presses yield no reward, that does not dampen the rat’s enthusiasm. Rather, as the rat continues to press, dopamine levels will go up in anticipation of the reward, which must be coming at any moment! When the reward finally comes, it feels great, but the heightened levels of dopamine make the rat continue to press, in anticipation of the next reward, which will come... after some unknown number of presses, so just keep pressing! There is no off-ramp in an app with a bottomless feed; there is no signal to stop.

These first three steps are classic behaviorism. They deploy operant conditioning as taught by B. F. Skinner in the 1940s. What the Hooked model adds for humans, which was not applicable for those working with rats, was the fourth step: investment. Humans can be offered ways to put a bit of themselves into the app so that it matters more to them. The girl has already filled out her profile, posted many photos of herself, and linked herself to all of her friends plus hundreds of other Instagram users. (Her brother, studying for an exam in the room next to hers, has spent hundreds of hours accumulating digital badges, purchased “skins,” and made other investments in video games such as Fortnite and Call of Duty .)

At this point, after investment, the trigger for the next round of behavior may become internal . The girl no longer needs a push notification to call her over to Instagram. As she is rereading a difficult passage in her textbook, the thought pops up in her mind: “I wonder if anyone has liked the photo I posted 20 minutes ago?” An attractive off-ramp appears in consciousness (step 1). She tries to resist temptation and stick with her homework, but the mere thought of a possible reward triggers the release of a bit of dopamine, which makes her want to go to Instagram immediately. She feels a craving. She goes (step 2) and finds that nobody liked or commented on her post. She feels disappointment, but her dopamine-primed brain still craves a reward, so she starts looking through her other posts, or her direct messages, or anything that shows that she matters to someone else, or anything that provides easy entertainment, which she finds (step 3). She wanders down her feed, leaving comments for her friends along the way. Sure enough, a friend reciprocates by liking her last post. An hour later, she returns to her study of photosynthesis, depleted and less able to focus.

Once the user’s own feelings are enough to trigger a behavior that gets variably rewarded, the user is “hooked.” We know that Facebook intentionally hooked teens using behaviorist techniques thanks to the Facebook Files—the trove of internal documents and screenshots of presentations brought out by the whistleblower Frances Haugen in 2021. In one chilling section, a trio of Facebook employees give a presentation titled “The Power of Identities: Why Teens and Young Adults Choose Instagram.” The stated objective is “to support Facebook Inc.–wide product strategy for engaging younger users.” A section titled “Teen Fundamentals” delves into neuroscience, showing the gradual maturation of the brain during puberty, with the frontal cortex not mature until after age 20. A later photo shows an MRI image of a brain with this caption:

The teenage brain is usually about 80% mature. The remaining 20% rests in the frontal cortex.... At this time teens are highly dependent on their temporal lobe where emotions, memory and learning, and the reward system reign supreme.

A subsequent slide shows the loop that Facebook’s designers strive to create in users and notes the points of vulnerability (see Figure 5.4).

Many other slides in the presentation indicate that the presenters were not trying to protect the young woman in the center from overuse and addiction; their goal was to advise other Facebook employees on how to keep her “engaged” for longer with rewards, novelty, and emotions. Suggestions include making it easier for teens to open multiple accounts and implementing “stronger paths to related interest content.”

Figure 5.4. Screenshot of an internal Facebook presentation, brought out by Frances Haugen. The caption says, “Teens’ decisions and behavior are mainly driven by emotion, the intrigue of novelty and reward. While these all seem positive, they make teens very vulnerable at the elevated levels they operate on. Especially in the absence of a mature frontal cortex to help impose limits on the indulgence in these.” (Source: The Facebook Files, section 42/15, p. 53.) [56]

In her book Dopamine Nation , the Stanford University addiction researcher Anna Lembke explains how addiction plays out in her patients, who suffer from a variety of drug and behavioral addictions (such as gambling, shopping, sex). Increasingly in the 2010s, she began to treat teenagers who had digital addictions. Like people with heroin and cocaine addictions, those addicted to digital activities found that “nothing feels good anymore” when they were not doing their preferred activity. The reason is that the brain adapts to long periods of elevated dopamine by changing itself in a variety of ways to maintain homeostasis. The most important adaptation is by “downregulating” dopamine transmission. The user needs to increase the dosage of the drug to get the pleasure back.

Unfortunately, when an addicted person’s brain adapts by counteracting the effect of the drug, the brain then enters a state of deficit when the user is not taking the drug. If dopamine release is pleasurable, dopamine deficit is unpleasant. Ordinary life becomes boring and even painful without the drug. Nothing feels good anymore, except the drug. The addicted person is in a state of withdrawal, which will go away only if she can stay off the drug long enough for her brain to return to its default state (usually a few weeks).

Lembke says that “the universal symptoms of withdrawal from any addictive substance are anxiety, irritability, insomnia, and dysphoria.” [57] Dysphoria is the opposite of euphoria; it refers to a generalized feeling of discomfort or unease. This is basically what many teens say they feel—and what parents and clinicians observe—when kids who are heavy users of social media or video games are separated from their phones and game consoles involuntarily. Symptoms of sadness, anxiety, and irritability are listed as the signs of withdrawal for those diagnosed with internet gaming disorder. [58]

Lembke’s list of the universal symptoms of withdrawal shows us how addiction magnifies the three other foundational harms. Most obviously, those who are addicted to screen-based activities have more trouble falling asleep, both because of the direct competition with sleep and because of the high dose of blue light delivered to the retina from just inches away, which tells the brain: It’s morning time! Stop making melatonin! [59] Also, while most people wake up multiple times during the night and then fall right back to sleep, people who have become addicted will often reach for their phones and start scrolling.

Lembke writes, “The smartphone is the modern-day hypodermic needle, delivering digital dopamine 24/7 for a wired generation.” [60] Her metaphor helps to explain why the transition from play-based childhood to phone-based childhood has been so devastating, and why the crisis showed up so suddenly in the early 2010s. Millennial adolescents in the 1990s and early 2000s had access to all kinds of addictive activities on their home computers, and some of them did get addicted. But they couldn’t take their computers with them everywhere they went. After the Great Rewiring, the next generation of adolescents could, and did.

To see the far-reaching effects of the transition to smartphones, imagine a sleep-deprived, anxious, and irritable student interacting with fellow students at school. It’s not likely to go well, especially if her school allows her to keep her phone with her during the school day. She’ll use much of lunchtime and time between classes to catch up on social media, rather than having the synchronous, face-to-face hangout time she needs for healthy social development, thereby further compounding her feelings of social isolation.

Now imagine a sleep-deprived, anxious, irritable, and socially isolated student trying to focus on her homework as off-ramps beckon from the phone lying faceup on her desk. Her impaired executive abilities will strain to keep her on task for more than a minute or two at a time. Her attention is fragmented. Her consciousness becomes “the confused, dazed, scatterbrained state” that William James said is the opposite of attention.

When we gave children and adolescents smartphones in the early 2010s, we gave companies the ability to apply variable-ratio reinforcement schedules all day long, training them like rats during their most sensitive years of brain rewiring. Those companies developed addictive apps that sculpted some very deep pathways in our children’s brains. [61]

On the Benefits of Social Media for Adolescents

In 2023, the U.S. surgeon general, Vivek Murthy, issued an advisory discussing the effects of social media use on youth mental health. [62] The advisory warned that social media poses “a profound risk of harm to the mental health and well-being of children and adolescents.” His 25-page report outlined the potential costs and benefits of social media use. Regarding benefits, he stated,

Social media can provide benefits for some youth by providing positive community and connection with others who share identities, abilities, and interests. It can provide access to important information and create a space for self-expression. The ability to form and maintain friendships online and develop social connections are among the positive effects of social media use for youth. These relationships can afford opportunities to have positive interactions with more diverse peer groups than are available to them offline and can provide important social support to youth. The buffering effects against stress that online social support from peers may provide can be especially important for youth who are often marginalized, including racial, ethnic, and sexual and gender minorities.

These benefits all sound plausible, and indeed the surgeon general was drawing on surveys showing that many teens say that they obtain these benefits from social media. For instance, a 2023 Pew report found that 58% of teenagers report that social media helps them feel more accepted, 71% saw it as a creative outlet, and 80% felt more in touch with their friends’ lives. [63] A 2023 Common Sense Media report found that 73% of girls report having fun daily on TikTok, and 34% said their lives would be worse if they did not have access to the platform. Sixty-three percent of girls say they have fun daily on Instagram, with 21% saying their lives would be worse without it. [64]

Certainly, these digital platforms offer fun and entertainment, as television did for previous generations. They also confer some unique benefits for specific groups such as sexual minority youth and those with autism—where some virtual communities can help soften the pain of social exclusion in the real world. [65]

However, unlike the extensive evidence of harm found in correlational, longitudinal, and experimental studies, there is very little evidence showing benefits to adolescent mental health from long-term or heavy social media use. [66] There was no wave of mental health and happiness breaking out around the world in 2013, as young people embraced Instagram. Teens are certainly right when they say that social media gives them a connection with their friends, but as we’ve seen in their reports of increasing loneliness and isolation, that connection does not seem to be as good as what it replaced.

A second reason why I am skeptical of claims about the benefits of social media for adolescents is that these claims often confuse social media with the larger internet. During the COVID shutdowns I often heard people say, “Thank goodness for social media! How would young people have connected without it?” To which I respond: Yes, let’s imagine a world in which the only way that children and adolescents could connect was by telephone, text, Skype, Zoom, FaceTime, and email, or by going over to each other’s homes and talking or playing outside. And let’s imagine a world in which the only way they could find information was by using Google, Bing, Wikipedia, YouTube, [67] and the rest of the internet, including blogs, news sites, and the websites of the many nonprofit organizations devoted to their specific interests. [68]

A third reason for skepticism is that the same demographic groups that are widely said to benefit most from social media are also the most likely to have bad experiences on these platforms. The 2023 Common Sense Media survey found that LGBTQ adolescents were more likely than their non-LGBTQ peers to believe that their lives would be better without each platform they use. [69] This same report found that LGBTQ girls were more than twice as likely as non-LGBTQ girls to encounter harmful content related to suicide and eating disorders. Regarding race, a 2022 Pew report found that Black teens were about twice as likely as Hispanic or white teens to say they think their race or ethnicity made them a target of online abuse. [70] And teens from low-income households ($30,000 or less) were twice as likely as teens from higher-income families ($75,000 or higher) to report physical threats online (16% versus 8%).

My fourth reason for skepticism is that these discussions of benefits rarely consider the age of the child. All of the benefits sound plausible for older teens, but do we really think that 12-year-olds need Instagram or TikTok to “connect” them with strangers instead of simply seeing their friends in person? I cannot see any justification for not enforcing the current minimum age of 13 for opening accounts on social media platforms.

We need to develop a more nuanced mental map of the digital landscape. Social media is not synonymous with the internet, smartphones are not equivalent to desktop computers or laptops, PacMan is not World of Warcraft, and the 2006 version of Facebook is not the 2024 version of TikTok. Almost all of it is more harmful to preteens than to older teens. I’m not saying that 11-year-olds should be kept off the internet. I’m saying that the Great Rewiring of Childhood, in which the phone-based childhood replaced the play-based childhood, is the major cause of the international epidemic of adolescent mental illness. We need to be careful about which kids have access to which products, at which ages, and on which devices. Unfettered access to everything, everywhere, at any age has been a disaster, even if there are a few benefits.

In Sum

In this chapter I described the four foundational harms of the phone-based childhood. These are profound changes to childhood caused by the rapid technological shift of the early 2010s. Each one is foundational because it affects the development of multiple social, emotional, and cognitive abilities.

The sheer amount of time that adolescents spend with their phones is staggering, even compared with the high levels of screen time they had before the invention of the iPhone. Studies of time use routinely find that the average teen reports spending more than seven hours a day on screen-based leisure activities (not including school and homework).

The opportunity cost of a phone-based childhood refers to everything that children do less of once they get unlimited round-the-clock access to the internet.

The first foundational harm is social deprivation. When American adolescents moved onto smartphones, time with friends in face-to-face settings plummeted immediately, from 122 minutes per day in 2012 down to 67 minutes per day in 2019. Time with friends dropped further because of COVID restrictions, but Gen Z was already socially distanced before COVID restrictions were put in place.

The second fundamental harm is sleep deprivation. As soon as adolescents moved from basic phones to smartphones, their sleep declined in both quantity and quality, around the developed world. Longitudinal studies show that smartphone use came first and was followed by sleep deprivation.

Sleep deprivation is extremely well studied, and its effects are far reaching. They include depression, anxiety, irritability, cognitive deficits, poor learning, lower grades, more accidents, and more deaths from accidents.

The third fundamental harm is attention fragmentation. Attention is the ability to stay on one mental road while many off-ramps beckon. Staying on a road, staying on a task, is a feature of maturity and a sign of good executive function. But smartphones are kryptonite for attention. Many adolescents get hundreds of notifications per day, meaning that they rarely have five or 10 minutes to think without an interruption.

There is evidence that the fragmentation of attention in early adolescence caused by problematic use of social media and video games may interfere with the development of executive function.

The fourth fundamental harm is addiction. The behaviorists discovered that learning, for animals, is “the wearing smooth of a path in the brain.” The developers of the most successful social media apps used advanced behaviorist techniques to “hook” children into becoming heavy users of their products.

Dopamine release is pleasurable, but it does not trigger a feeling of satisfaction. Rather, it makes you want more of whatever you did to trigger the release. The addiction researcher Anna Lembke says that the universal symptoms of withdrawal are “anxiety, irritability, insomnia, and dysphoria.” She and other researchers find that many adolescents have developed behavioral addictions that are very much like the way that people develop addictions to slot machine gambling, with profound consequences for their well-being, their social development, and their families.

When we put these four foundational harms together, they explain why mental health got so much worse so suddenly as soon as childhood became phone- based.