Haidt examines the changes in childhood brought about by the introduction of smartphones and social media. He uses a thought experiment to illustrate this transformation, comparing a pre-2007 world to the smartphone-dominated reality of the present, when both adults and children are constantly engaged with their devices.

Haidt identifies five metrics crucial for healthy human development: slow-growth childhood, free play, attunement, social learning, and sensitive periods during which specific experiences must occur.

Slow-Growth Childhood

Humans have a unique pattern of growth, characterized by rapid growth in early years, a slow period during middle childhood, and a growth spurt during puberty. This slow-growth phase allows children to absorb cultural knowledge and skills essential for adult life. Evolutionarily, this extended childhood period provided time for learning and mastering the social and cultural practices of human societies.

Free Play

Free play, defined as self-directed and intrinsically motivated activity, is fundamental for developing social, cognitive, and physical skills. It involves activities like running, climbing, and role-playing games, which teach children how to navigate their environment, resolve conflicts, and build social bonds. In contrast, modern screen-based activities often lack these benefits. Haidt emphasizes that play involving physical risk is particularly valuable as it teaches children to manage real-world dangers.