I've won the lottery a while ago and I am cruising the Whitsundays on my new yatch. I find an ideal snorkelling spot, weigh anchor, and it's into the water. Here is a photo in case you are having difficulty following my daydream.

Oops, the boss is coming, I had better start concentrating again.

That ability to rapidly shut down your daydreaming and focus is a skill that young adults find quite simple. As we grow older it becomes more difficult, which may explain why The Green Man, being an ancient woodland spirit, is daydreaming most of the time.

Washington University in St. Louis researchers are investigating this phenonemon and using it as a tool for detecting the early stages of Alzheimer's disease.

Recent research has provided mounting evidence supporting the existence within the brain of a "default network," a set of interconnected brain areas that carry out routine, passive mental processes, such as monitoring the environment, registering internal emotions and other forms of largely undirected thought and reflection.

Through this study researchers detected significant differences in the timing and magnitude of changes in the "default network" activity in older people compared with young adults and particularly in those with Alzheimer's disease.

The Green Man finds himself drifting off again - back to the yatch. "Make sure that champagne is chilled James. I'll have some with the char-grilled coral trout after my swim."

Read more here.