Stephen LaBerge's book explains, in detail, how they would communicate with lucid dreamers during their research. I don't remember how the researchers signaled the subjects, but if I remember correctly, the subjects would communicate with researchers primarily through eye movements. I can't say if the methods are related at all, but the book is worth a read.

My thought too. The title appears to assume there's nothing special about the 'communicating' but there is about the 'practicing'. Should it not be 'New research suggests people can practice skills and even communicate while dreaming'. I would like to know more.