It was a practical session in the psychology class. The professor showed a large cage with a male rat in it. The male rat was in the middle of the cage. Then the professor kept a piece of cake on the side, and kept a female rat on the other side.
The male rat went towards the cake and ate it. Then, the professor changed the cake and put some bread, The male rat ran towards the bread.
This experience went on with the professor changing the food every time. And, every time, the male rat ran towards the food item, and never towards the female rat.
Professor concluded: "This experiment shows that food is the greatest strength and attraction."
Then, one student from the back rows said: "Sir, why don't you change the female rat? She may be his wife!"