No man is an island: we act together, think together and even remember together. Elderly couples have interconnected memory systems, working together to deftly remember their shared past. New research in the Journal of Personal and Social Relationships shows that platonic friends see themselves similarly. In a sample of 216 students and online recruits, Nicole Iannone and colleagues found high agreement with items such as “my best friend and I can remind each other of things we know,” part of a scale measuring “transactive memory systems” – shared systems of recording, storing and recalling information. Ratings were even higher when participants were referring to friendships that were longer, more trusting or of a higher quality overall.
Gender had no effect on degree of interconnection, but seemed to shape the kind of interconnection. In a second study with 340 participants, same-sex friendships were more likely to have overlap in similar memory areas, such as both knowing a lot about movies, whereas mixed-sex friends had distinctive areas of expertise – suggesting a good team-up for a trivia night. The authors note that in their sample, memory interdependence was the single best predictor of friendship quality, more even than relationship length or a general measure of trust, raising the idea that putting faith in someone else to preserve your past is an important facet of long-term intimacy.