The more vivid and concrete an image is the more likely it is to stick in the mind. Elaboration is the key to the memory palace. Some people's memory palaces are rather barren, however. Notably, people who suffer from serious depression.
For about a year now, I have been searching for a new memory tool. Something that would be relentless until my task was completed. In January, 2012, the "Today" show reported that mental capacity starts to diminish at the average age of 45. I wrote that down, and I'm glad I did.