Psychologist David Rubin has difined something that he calls' a memory bump. This refers to the idea that middle-aged and old adults remember most strongly things that happened between the agree of 10 and 30. This group is significantly different from adults in their early twenties, when important memories chang constantly. In his study Rubin asked college students to tell him their most important memories. When asked the same question six months last only 12 percent of the college students repeated the same story. When we are so young, we are still writing our own life story and there are often many major changs, such as our first job, marriage and children. As a result, the relative importance of events in our lives is always changing.