I was recently doing some reading on memory and how people often need others to remember certain events. It's not that we can't remember them on our own, but with as much information as we receive and are forced to sort through on a daily basis we can't possibly do it all alone. So our brains have formulated a way for us to remember everything. In turn we don't remember EVERYONE we know's phone number, but we know where to go to find it.
There is however a strong correlation between couples and having a somewhat combined memory. This seems to come in to play quite often with one part of the couple being the one who plans the schedule and the other taking care of household things.
They even did a study of couples who had been together longer than 3 months; some of the couples were kept together and some were split up and paired with someone else. They were then given paragraphs to read and remember. The couples who were together remembered twice as much as the groups of people who had never met.
Until recently I'd always been the more responsible one in the relationship, thus the one who paid the bills, kept the schedule, remembered all the b-days, so when reading this I nod my head affirmatively and understand exactly where the author is coming from.
It is said that this is why breakups are so hard on people, not only are you loosing the companionship, but you're also losing those stored memories. Maybe this is yet another reason humans are meant to live in groups and partnerships. hmmmm.