One is the number of people who do it or the number of times it's being done, and then there must be some variable of intensity. It makes a difference if someone is absolutely intensely involved with an idea compared with someone who just flicks through a magazine and sees a picture of your particular kind of thing for a few seconds and it's very superficial. If somebody in solitude works away in an extremely intense way it may indeed set up a morphic field. I live in a very small town and compete in a couple larger towns. I wanted to do the local history of the Native Americans that lived here, but found everyone was doing that, so I gave up.
Strange things happen.
I first heard this applied to discoveries in the field of science when scientists, working completely apart from each other and separated by great distance, make breakthroughs in their research in the same field of study at almost the same time. The answer eluded me for about a week until one day it knocked me on my ear. Our life's expierences. Think about it for a second, nobody will ever see the world as you do, and even though you tell them the stories of your life, they will envision it in terms they can relate to. Say I met a guy named Ralph.