Give or Take a Banana

An experiment is conducted in which five rhesus monkeys were placed in a cage together with a banana hanging high on a rope outside the reach of the monkeys.  A step ladder was placed in the cage that would enable the monkeys to reach the banana.  Whenever one of the monkeys attempted to climb and reach for the banana, ALL monkeys were sprayed with freezing cold water.

After a few attempts, all the monkeys learned the association between reaching for the banana and the group collective punishment of being sprayed with freezing water.  There was no longer need for the water; no monkeys would attempt to reach the banana.

The researcher then replaced one of the five monkeys with a new monkey. The new monkey, not aware of the icy water treatment, tried to reach for the banana. Within a fraction of a second the other four monkeys attacked him again and again, until he no longer tried to reach the banana.  One by one, the monkeys who had experienced the original icy water treatment were replaced by a new monkey.  With the introduction of each new monkey, the other monkeys would attack him until he quit trying for the banana.

Eventually, the cage was populated by five new monkeys, none who had experienced the icy water treatment.  The experimenter then introduced a new monkey to the cage. When this monkey tried to reach for the banana, all five monkeys attacked him.

The story goes that even though none of these monkeys knew about the collective punishment of icy water, somewhat along the way they learned that reaching for the banana is not allowed. They become the guardians of this rule without knowing its purpose.