Ask: What if you were told that what you think is drawn in the picture was incorrect?
Note: For most the reaction is one of disbelief leaving the viewer to defend their vision. Instead of arguing, let us look at what each picture contained.
In this picture they either saw an old woman or a young woman.
Whichever they saw have them look at the picture again and look for the other. The picture was drawn to show that the young woman remains in her even as she ages. The older woman sees this as she reflects on her life. Notice the older woman is looking down while the younger woman is looking to the back.