Things continue to exist even when we can’t see them, but until we’re old enough to understand that notion, it’s out of sight, out of mind. Object permanence is one of those things we figure out when ...

The work of Jean Piaget shaped our understanding of cognitive development in children, and it also gave us several tasks that we can use to study other animals. One classic issue studied by Piaget is ...

“Certain objects,” Dinah Lenney writes, “not always the ones we’d expect to keep or remember or dream about, insinuate themselves—take on a lustre in which we are reflected.” It’s quite the thought to ...