Well, they're anything but. I recently met with Julia Shaw, a criminal psychologist who specializes in the science of memory. "I am a memory hacker," Shaw told me. "I use the science of memory to make you think you did things that never happened."

Implanting a false memory, it turns out, is alarmingly easy to do.

Shaw, a Canadian now living in London, was in Toronto to promote her new book, The Memory Illusion. In it, she describes how false memories can be deliberately placed in people's brains—leading to false police confessions that could send the wrong person to jail, or detailed accounts of alien abductions that (almost certainly) never happened.

"A memory is a network of brain cells," Shaw explained to me. That network, which stretches across different regions of the brain, is constantly being updated. It's an important function that allows us humans to learn new things and to problem-solve, among other skills. But as a result, it "can be manipulated," she continued. "Each time you tell a story, you change the memory," maybe dropping in new details, weaving in tidbits you really heard from somebody else, or forging new, and possibly inaccurate or misleading, connections.