This technique was included in a creative writing module that I studied as part of my OU literature Degree course. You are probably already familiar with it but if not - the following has been culled from my course reader:
A technique developed by Gabrielle Lusser Rico in her book Writing the Natural Way (1983)
Based on the separate functions of the brain's two hemispheres
Aims to bypass the analytical functions of the brain which might initially constrain creative writingClustering helps us to move backwards and forwards between different areas of the brain as needed. It suppresses the analytical mode that we often go into when we begin to start thinking about writing something. It is more like drawing or sketching than writing and helps us to begin writing more easily and coherently.
How to do it -
This is a fast exercise. Spend no more than 3 minutes on a cluster
Take a blank sheet of paper and choose a word or phrase connected with what you want to write about
Write this word or phrase in the centre of the page and circle it
Write down every connection that comes into your head
The words or phrases that you write should fan out from the initial circle like a branch
Don't worry about being neat. Here's a sample cluster (not written by me!)
Once you have drawn a cluster the idea is that you look for things in it that you find particularly interesting and use them as the basis for free writing exercises, which will further release the creative imagination.