Very interesting little test. I wonder if you've tried it at different times of the day or different states of mind? The ratio of neurotransmitter chemicals that are dominant in the brain changes widely with different conditions, which affects function.
For example, I just tried the test and felt like it was a great effort to visualize the star. I've just had a cup of coffee (similar to amines). But this morning, transitioning from a very restful sleep (when acetylcholine levels would have been high), I was having clear, partially directed mental images, similar to dreams, but wakeful.
EDIT: And even more interestingly (to me) I'm having a very _easy_ time with the other exercises you linked below...
For example, I just tried the test and felt like it was a great effort to visualize the star. I've just had a cup of coffee (similar to amines). But this morning, transitioning from a very restful sleep (when acetylcholine levels would have been high), I was having clear, partially directed mental images, similar to dreams, but wakeful.
EDIT: And even more interestingly (to me) I'm having a very _easy_ time with the other exercises you linked below...