I found this on page 67 of Malcolm Gladwell’s The Bomber Mafia:

“The psychologist Daniel Wagner has this beautiful concept called transactive memory, which is the observation that we don’t just store information in our minds or in specific places. We also store memories and understanding in the minds of the people we love.

“You don’t need to remember your child’s relationship to her teacher because you know your wife will; you don’t have to remember how to work the remote because your daughter will.

“That’s transactive memory. Little bits of our memory reside in other people’s minds. Wagner has a heartbreaking riff about what one member of a couple will say after the other member dies – that some part of him or her died along with the partner. That, Wagner says, is literally true. When your partner dies, everything you have stored in that person’s brain is gone.”