There is a time-honored story about an old farmer who was persuaded by his nephew to visit the big city. The young man proudly took the farmer on a tour of the large metropolis.

At one point as they walked down the street the old man suddenly stopped and asked, "Did you hear that?"

The young man looked at the milling pedestrians and the traffic and replied, "Hear what?"

"A cricket," the old man said as he walked toward a little tuft of grass growing out of a crack next to a tall building. Sure enough, there tucked in the crack was a cricket.

The young man was amazed. "How could you pick up the sound of a cricket in all this noise?" he asked.

The old farmer didn't say a word and just reached into his pocket, pulled out a couple of coins and dropped them on the sidewalk. Immediately a number of people began to reach for their pockets or look down at the sidewalk.

The old man observed, "We hear what our ears are trained to hear."