New Delhi, April 14 -- "You scroll without thinking and lose track of time," admits Ramón, a Spanish 15-year-old, of his habits on social media. "You see girls sexualising themselves, car crashes, really violent stuff," he continues. "Everyone I know sees that kind of content." At school, in particular, he thinks, social-media use "really messes with your head and with your attention".

Yet the Spanish government's plan to bar children under 16 from social media, announced earlier this month, leaves Ramón cold. His contemporaries would easily find ways around it, he thinks. His mother agrees. And given that children will inevitably be on social media one way or another, she would rather the government try to curb the most harmfu...