First of all I plan to look into this belief from a very literal point of view by asking the question: can memory be improved by quality of health; i.e. can physical exercise improve the strength (quality) of our memory?
Secondly, I will address the more common variation of this belief by asking: can mental workshops, games, and exercises non-related to specific memories increase the availability of those memories or improve future ability to form and retain new memories?
Next, in my Getting Started page I have included a list of readings which will give you a starting point from which you can explore your own questions of this popular belief.
Have you heard of this belief in different way? Do you know anybody who agrees with parts of this belief? If so I'd like to encourage you to post any comments and let me know! We'll be able to look into these ideas together.