I have been pocking around to generate a visualization that can help understand how the users interacted with the map in our virtual retrieval experiment. It was fun to discover that there were some zones more used than others in the map, namely the central upper quadrant and the central left and right quadrants. The image below shows the density of visualization of results.
The map has been subdivided into 9 quadrants. In each quadrant is possible to see three big numbers. The upper one is the number of results that fall into the sector (even if you see few points there might be super impositions between similar queries). The lower-left big number in blue is the number of the items that have been read by the users. The red is the number of items that have been selected by the users in that quadrant.