You and a friend both recall the childhood you shared, but your memories differ, and not just in small ways. This sort of thing happens to many people. Who is right and who is wrong?
Maybe both are wrong. A recent study published in the Journal of Neuroscience suggests that recalling a memory more often actually makes it less accurate.
Why? Because instead of remembering what actually happened, we recall the memory of the last time we remembered the original event, complete with any change that may have been introduced at that moment.
Researchers at the School of Medicine at Northwestern University in Chicago asked people to relate objects to locations on a grid over the course of three days. They found that while recollections on the second day had only a few inaccuracies, by the third day people took those second-day mistakes as their real memories.
The implications are profound. Just like we "cannot step into the same river twice", now it seems that we cannot accurately recall the same moment just as it was more than once, if ever.
But is that a good thing, or a bad thing? That depends, we suppose, on the memory. Sometimes we may prefer a distorted version of the past.