The more I look the old people, more I’m convinced that the memory is like any other artifact: it gets oxided and we lose it with the time. Formally speaking, the memory is the capacity to retain information to use it later. When the people gets old, memory capacity is reduced and, some people, have Alzheimer. For example, my grandmother confuse the names of her children and grandchildren. It's the same when she changes something of place, she forgets where she put it. Definitely my grandmother goes 10/7.