I remember reading about a study of luck once. They had a bunch of people rate how lucky they tended to be, and then had each person count how many pictures were in a section of newspaper. The people who said they were lucky finished much faster than the rest - they noticed that the second page of the newspaper contained a headline, or maybe it was a caption, stating how many pictures there were.

The opportunity to cut the count short was there for all of them, but the "lucky" people were much more likely to notice and use it.