Correlation Is Not Cause and Effect

The best story I have heard about the confusion between cause and effect was from my days as an economics major. The story that Frank Knight of the University of  Chicago told came from Alfred Radcliffe-Brown, a social anthropologist. Here’s how it goes:

Many years ago, a group of missionaries in the eastern part of Africa decided to teach the natives better farming methods. They concluded that the way to do it rapidly was to get a promising young man from each tribe, teach him the needed farming skills, and then send him back to practice the better methods, whereupon the entire tribe would follow the example.

One of the young men selected went back to his tribe in Portuguese, East Africa. He duly plowed his field instead of punching holes in the dirt with a stick, cultivated his crop, and soon had a splendid showing. Even more impressive was the fact that it was a dry year and no other field than his was able to yield a crop at all.

This fact naturally caused some uneasiness among the people. Because the young man did not use farming practices sanctioned by the ancestral gods, the tribe members started to talk of witchcraft, as that was part of their belief system. So without any ceremony or any considerable discussion, the people took the innovator, cut him into small pieces, and planted a piece of him in each field of the tribe.

The next year everybody had a good crop.