Another interviewee, a 27-year-old from Britain, said he used A.I. as “an advanced Google search” for his personal life, with the power to remember a sequence of emotion the next time he feels it. He felt more comfortable taking his feelings to ChatGPT before sharing them with another person. Intrusive thoughts are to be nullified; friends are there for lightness and laughter.

Synthetic intimacy creates what economists call negative externalities — the hidden costs that fall not on the person making the choice but on the relationships that are changed, ever so slightly, around you. Mike Jeffcoat, a psychotherapist of 14 years, told me that he doesn’t share the same challenging emotions with his friends that he shares with A.I. He prefers to do his spiritual and emotional processing alone. “Who can and will be truthful, hold space and be competent with one’s confusing subconscious content?” he asked.

Intimacy is accumulated through repeated acts of exposure — touch, feelings, ideas, trust. It is the capital of human connection, transferring the sense to one another that we are seen, understood and safe. Every time a chatbot performs a substitute “I understand you” or “I think this decision feels most you,” the words we have all come to rely on to convey human meaning are slightly cheapened, slightly less human.

It’s easy not to notice our friends withdrawing. Intimate A.I. conversations are not uncommon: Nearly two-thirds of adolescents who use chatbots said they were searching primarily for friendship or advice, according to a recent survey. But frequent A.I. use is often considered taboo. One 34-year-old I spoke to was afraid that the extent of her Claude use would “freak out” the guy she was seeing. After they broke up, she created an A.I. version of him to better understand their breakup. “It’s a processing tool,” she shared with me — in confidence, having told nobody else in her life — so she could find closure on her own terms. If the attention economy of the 2010s made intimate life feel constantly public, the intimacy economy promised the opposite: relationships with one’s own chatbot, seen by no one else.

A.I. has become a kind of social sealant, filling the gaps in young people’s relationships: coaching men to plan dates that outromance their rivals, supplying words of condolence our friends couldn’t quite find. Lately, it’s stopped being so invisible. “So my A.I. told me …” is now a casual part of my friends’ conversations. One friend texted me after he had come home from a good date, for once, elated and desperate to share it with someone. With his roommates asleep, he primed his chatbot: “Be my flatmate after I’ve just come home from this date.” I quickly texted back, so he spoke to me. But if I hadn’t, that conversation would have strengthened his connection to Claude instead, at our friendship’s expense.