The moment was small, almost imperceptible. As the psychologist Jonathan Haidt spoke via video link from New York about the dangers of screens for the very young, the interpreter at the lectern in Mexico City relayed a personal anecdote: when his son was two, giving him a phone released dopamine instantly and was harmful. She then offered a recommendation to avoid screens before age two, waiting ideally until six, so the device did not become a “digital pacifier.” President Claudia Sheinbaum, listening intently, cut in. “No, he didn’t say that,” she corrected. “He said it’s a public health issue.” The interpreter adjusted without missing a beat, and the briefing continued, but the exchange laid bare the urgency of the message being delivered that morning.

That message came from two figures who had once helped build the very systems now under scrutiny. Arturo Béjar, a former director at Meta and designer of its user protection system, walked the room through the six design elements that make platforms compulsive: infinite scroll, autoplay, recommendation algorithms, constant notifications, popularity metrics, and the social pressure to remain connected. He presented data from a study of 240,000 users: one in five adolescents receives content in a week that makes them feel bad about their body; one in eleven is exposed repeatedly to material about self-harm or suicide. “This is a design issue,” Béjar said. “It’s an algorithm that captures attention. The more time you spend there, the more damage it causes.”

Haidt, a social psychologist at New York University, placed the shift in a broader cultural frame. Between 2010 and 2015, he argued, childhood moved from a play-based model to a phone-based one, a transformation that has produced a generation with higher rates of depression, anxiety, eating disorders, and attention deficits. He accused tech companies of using algorithms and artificial intelligence to hook children for profit and then lying about it. His recommendations were concrete: ban smartphones during the entire school day and raise the minimum age for social media accounts to 16, following the example of Australia, where, he said, a similar measure had already reduced use by 30 percent in six months.

The Mexican government signalled it was listening. Sheinbaum framed the issue not as a matter of individual choice or even national security, but as a public health challenge akin to drug consumption. “If we only see the commercialisation, distribution, and production, it becomes solely a security issue,” she said. “If we don’t see the consumption side, we’re missing a part.” She noted that even in the remote Sierra Tarahumara, most children now have access to a cellphone, and that 70 percent of parents support restricting phones during school hours. A formal proposal is expected by the end of August, following a series of public forums, and will be paired with a national mental health programme called “ABC de las emociones,” distributing millions of guides to families and schools.

As the conference ended, the image that lingered was not of a politician or a tech whistle-blower, but of a child in a far-off mountain community, a phone in hand, scrolling through an infinite feed designed far away to hold her attention. The debate, Sheinbaum insisted, was not about prohibition but about a collective decision on what kind of childhood the country wanted to reclaim.