Do not skim. Do not skim. Do not skim.
http://quizstop.com/askread.htm
Your score will be affected if you do poorly on the Comprehension Test following the quiz.
The trick is to see this lady spinning in each direction: clockwise or counterclockwise. Most will see it orienting in one direction only. It's difficult to switch it in our minds. For many the task will be impossible.
http://mindbluff.com/clockwise.htm