Why doesn’t everyone remember the same details of an event?

This post was inspired by the following question: My friend and I went ice skating together, but we remember different things from the afternoon. How can our memories be so different when we were together the whole time? 

There are two main reasons why, even when people experience the same event, they won’t remember exactly the same details.

First, we will remember what we were paying attention to at the time.  Maybe you were cold, and focused on whether there was hot chocolate for sale.  Meanwhile, your friend may have been focused on other things – maybe trying to avoid other skaters racing around the rink, or practicing some newly-learned ice skating techniques.  Those differences in what you were thinking about as you skated around the rink will affect what you remember from the afternoon.  You may remember the cold air as you skated and the delicious hot chocolate, while your friend may remember the crowded rink and the feeling of accomplishment as they completed their first spin on the ice.

Second, we discussed how memories are recalled by rebuilding cell connections.  Each person is going to build those connections in slightly different ways, and those differences are going to affect the way that content comes to mind.  So even if you and your friend were thinking of hot chocolate while skating around the rink, your brain connections may lead you to easily recall how cold you felt, while your friends’ brain connections may lead that detail to be forgotten.