Sail boat or cup

wolram

http://www.sciencedaily.com/releases...0911150046.htm

ScienceDaily (Sep. 17, 2008) — In work that could aid efforts to develop more brain-like computer vision systems, MIT neuroscientists have tricked the visual brain into confusing one object with another, thereby demonstrating that time teaches us how to recognize objects.

Just goes to show how easy we can be tricked.