I’ve known my two best friends since 9th grade. In that time, a lot has happened, and I’ve forgotten a lot of it. It’s not unusual now for one of them to say “Remember in high school, when this happened?” and for me to reply “Well now I do.” They’re always reminding me of things I’ve forgotten. They’re an extra hard drive for my limited memory capacity.
In science, this is known as a transactive memory system. Transactive memory systems (TMS) are repositories of knowledge that are shared between two or more people. A shared memory of events, like with me and my friends, above, can be part of it, but it’s also a way of calling up facts that other people know. If you say “Oh, what’s the movie that starts with that whistling cartoon rooster?” and I say “Robin Hood,” that’s transactive memory. You have access to my knowledge, and vice versa. But, it only works if we trust each other that we both know what we’re talking about, and that we know we can call on each other for the knowledge if we need it.
These systems have so far been studied in romantic relationships and work groups (coworkers, classmates, groups slapped together in the lab). A new paper published in the Journal of Social and Personal Relationships looks at transactive memory in the context of best friendships. The researchers asked people to answer questions about their relationship with their best friend—how satisfied and committed they were to the friendship, how long they’d been friends, things like that, as well as questions designed to measure the strength of their TMS, like “I trust that my best friend has credible knowledge.”