We've outsourced our memories to digital devices, and the result is that we no longer trust our memories. We see every small forgotten thing as evidence that they're failing us.

To the extent that experience is the sum of our memories and wisdom the sum of experience, having a better memory would mean knowing not only more about the world, but also more about myself.

It is forgetting, not remembering, that is the essence of what makes us human. To make sense of the world, we must filter it. "To think," Borges writes, "is to forget.

Over the last few millennia we've invented a series of technologies - from the alphabet to the scroll to the codex, the printing press, photography, the computer, the smartphone - that have made it progressively easier and easier for us to externalize our memories, for us to essentially outsource this fundamental human capacity.

All across Africa, the Pacific and the Americas, we find cultures that didn't know about mouth kissing until their first contact with European explorers. And the attraction was not always immediately apparent. Most considered the act of exchanging saliva revolting.

Growing up in the days when you still had to punch buttons to make a telephone call, I could recall the numbers of all my close friends and family. Today, I'm not sure if I know more than four phone numbers by heart. And that's probably more than most.

When we first hear [a] word, we start putting these associational hooks into it that make it easier to fish it back out at some later date.