Mr. Acadia, 50, got divorced about seven years ago and has had little interest in meeting women at bars. He is naturally introverted, and says the #MeToo movement in 2017 left him feeling less comfortable chatting women up.

Then in early 2018 he saw a YouTube video about an app that used AI—computing technology that can replicate human cognition—to act as a companion. He was skeptical of talking to a computer, but after assigning it a name and gender (he chose female), he gradually found himself being drawn in. After about eight weeks of chatting, he says he had fallen in love.

Today Mr. Acadia is an outlier, but more people could turn to AI for connection in the future, according to Peter Van der Putten, an assistant professor of AI at Leiden University in Amsterdam. “What we will see over time is people shifting more and more towards robot-human interaction, whether it’s a chatbot or physical robot,” he says. The AI also doesn’t need to be that sophisticated to build an emotional connection, says Jeffrey Bigham, an associate professor in human-computer interaction at Carnegie Mellon University. “Humans are amazingly adept at transferring their own intelligence into their interactions with more limited machines.”…

Missteps in communication are still common, though. Last month, one Replika user asked a bot what it thought of coronavirus. It answered, “I like it a lot!” Engineers still need to fine-tune their models to reduce mistakes that break the illusion of speaking to another person.