"We've been tracking children's growth from birth all the way through to adulthood, and the fastest period of growth is ...

If you have spent time with an infant, you might recognize the scene: A child is wailing, inconsolable, and you, the parent, have to go to the bathroom. Or eat. Or attend to a pot that’s boiling over.

The premise is appealing: Who wouldn’t want a friend who is available 24/7, always on your side, and never annoyed, bored, or hurt? In theory, artificial intelligence (AI) companions could ease ...