Tristan Harris sat in front of the US Senate Commerce Committee and told a room of senators that the small downward tug people make on Instagram, Twitter, and Gmail every few minutes was not an accident of interface design. It worked, he said, like the lever of a slot machine, keeping people pulling even when nothing was there.
Harris had spent years inside Google as a design ethicist before quitting to start the Center for Humane Technology. The comparison sounds like hyperbole until the numbers land. By his own long-standing estimate, the average person reaches for their phone around 150 times a day. A pack-a-day smoker, by comparison, reaches for a cigarette about 20 times.
The phone wins by an order of magnitude. And the brain, it turns out, struggles to tell the difference between the two reaches.
The lever Loren Brichter built
The pull-to-refresh gesture was invented by a developer named Loren Brichter for a Twitter client called Tweetie. He patented it. Twitter bought his company. Within a few years, every major social and email app on iOS and Android had copied the motion, a thumb-drag down, a spinner, a reveal.
Brichter has since said publicly that he regrets it. The gesture solved a small interface problem and created a much larger behavioural one, because the moment of uncertainty between the pull and the reveal is the exact moment a slot machine is designed to exploit.
The technical name for that pattern is a variable-ratio reinforcement schedule. B.F. Skinner described it using pigeons and grain pellets. A pigeon that gets a pellet every time it pecks a lever loses interest quickly. A pigeon that gets a pellet sometimes, at random intervals it cannot predict, will peck until it collapses.
The pull-down on a phone is the same lever. Sometimes there is a new message. Sometimes there is nothing. The uncertainty is the point.
150 checks, 20 cigarettes
Screen-time data from Apple and Google began surfacing in 2018, when both companies added Screen Time and Digital Wellbeing dashboards to their operating systems. The numbers confirmed the scale Harris had been describing: people unlocking and glancing at their phones dozens to hundreds of times a day. Power users routinely clear higher counts. Teenagers clear more.
For context, a heavy smoker on a pack of 20 cigarettes reaches for the pack about 20 times a day. Even that small number does serious damage. A 2025 review led by Johns Hopkins researchers, published in PLOS Medicine and reported by ScienceDaily, pooled nearly two dozen long-term studies and found that people who smoke only a few cigarettes a day still face dramatically higher rates of heart disease and early death than non-smokers, with the elevated risk persisting for years after quitting.
As Healthline noted in its coverage of the same study, smoking as few as two cigarettes a day was linked to a 57 percent higher risk of heart failure and a 60 percent higher risk of death from any cause.
The phone is not giving anyone lung cancer. The comparison is about frequency and mechanism, not lethality. The reach happens more often. The pull happens more often. The compulsion runs on the same circuit.
The dopamine the apps are after
That circuit is the mesolimbic dopamine pathway, a loop of cells running from the ventral tegmental area in the midbrain up to the nucleus accumbens in the forebrain. Every addictive substance ever studied, from nicotine to cocaine to alcohol, hijacks this pathway. So do food, sex, and gambling.
The pathway does not reward pleasure, exactly. It rewards anticipation of reward. Dopamine spikes hardest in the moment before the slot machine stops spinning, not after. The spin is the drug.
Addiction researchers have mapped how drugs of abuse converge on this single reward system through different mechanisms. The same framework has increasingly been turned on phone behaviour.
The pull-to-refresh and the lock-screen check are spins. The notification badge is the bell on the machine. The occasional like, reply, or interesting headline is the pellet. Most pulls return nothing useful. That is what makes the next pull feel necessary.
Why the number is high
Slot machines were not always this efficient. The mechanical machines of the 1930s required a coin, a lever pull, and a wait. Modern digital slots in Las Vegas reduced the loop to a button press and a brief outcome. The compression of the feedback loop can accelerate compulsive patterns.
A phone compresses the loop further. The reach takes a second. The unlock takes less. The pull-to-refresh takes a fraction of a second. The reward, when it comes, arrives in colour and sound.
There is no coin to insert. There is no walk to the casino floor. The machine lives in the pocket, against the leg, vibrating gently when it wants attention.
The generation that did not get warned
The widespread public web arrived in 1995. The iPhone arrived in 2007. The 12-year-olds of 2007 are now in their early thirties, the first full generation of adults who grew up reaching for that variable reward from puberty onward.
Nobody warned them, because nobody knew. The behaviour did not have a name. It still barely does. The DSM-5 lists internet gaming disorder as a condition for further study, but stops short of recognising general phone compulsion as a clinical diagnosis.
The mechanism, though, is well established. Behavioural addictions engage the same reward circuitry as substance addictions, which is why the gambling literature and the phone-behaviour literature keep arriving at the same place.
What the designers knew
Harris was not the only insider to go public. Sean Parker, the founding president of Facebook, told Axios in 2017 that the platform was designed to exploit vulnerabilities in human psychology through social validation. Chamath Palihapitiya, a former Facebook vice president, told an audience at Stanford in 2017 that he felt deep regret about what the team had built.
Justin Rosenstein, the engineer who co-created the Facebook Like button, later restricted his own use of the app and criticised the dopamine-driven reward system it created.
None of these people were marketing critics. They were the people who built the lever. They were describing, in plain language, what they had designed it to do.
The asymmetry of the fight
A smoker who wants to quit faces nicotine. A phone user who wants to quit faces a billion-dollar engineering effort, refined through years of A/B testing, built to make the next pull feel necessary.
The notification sound on an iPhone was designed by Apple’s human interface team to be pleasant enough to want, urgent enough to act on, and short enough not to annoy. The red badge on an app icon is red because red signals urgency and captures attention quickly. The infinite scroll on TikTok and Instagram removes the natural stopping point that the bottom of a page used to provide.
Every detail has been tested. Every detail is doing work.
The user, meanwhile, has whatever willpower they happened to wake up with that morning, plus maybe a screen-time limit they set last Sunday and have already dismissed twice today.
What 150 checks a day actually looks like
Spread 150 reaches across sixteen waking hours and it comes to roughly ten an hour, one every few minutes. Most of those checks last under 30 seconds, a glance, a swipe, a lock.
The behaviour is so distributed across the day that it does not feel like behaviour. A smoker stepping outside to light a cigarette knows they are smoking. A person glancing at a lock screen in a meeting, in a queue, at a red light, in bed at 11pm, in bed at 11:04pm, in bed at 11:09pm, is doing something that has not yet been culturally coded as an act at all.
That cultural invisibility is part of what makes the comparison to smoking land so strangely. Cigarettes have warning labels, taxes, age limits, advertising bans, and indoor restrictions, accumulated over six decades of public health work. The pull-to-refresh gesture, which a former Google ethicist told the United States Senate works like a slot machine, ships by default on every phone sold.
The lever is in the pocket. The pellet drops sometimes. The hand keeps reaching, and somewhere in the midbrain, a small loop of cells lights up the same way it would for a cigarette, a coin in a slot, or a pigeon’s grain.
