"Supervisor" joke

There were two workers digging in a ditch. Their supervisor was sitting against a brick wall reading a book.
After a while, one worker said to the other "How come we're over here working in the hot sun while he's over there reading a book?"
The other guy replied, "I don't know. Why don't you go ask him?"
So the first guy walked over to where the supervisor was sitting. The supervisor looked up and then went back to reading his book.
Finally the worker asked him, "How come you're over here reading, while we're digging in the sun?"
The supervisor looked at him for a moment and answered, "Intelligence." Then he continued reading.
After thinking about this for a minute, the worker asked, "How's that?"
The supervisor replied, "Let me show you." He held out his hand and said, "now, hit my hand as hard as you can."
The worker put down his shovel and proceeded to hit the supervisor's hand, but just before they collide, the supervisor moved his hand out of the way, causing the worker's hand to crash into the brick wall.
"OW! OK, I see now," said the worker, rubbing his hand as he walked back to the ditch.
The other worker looked up and asked, "Well, what'd he say?"
"He said' Intelligence'," responded the first.
"What?"
"Let me show you." The first guy looked around for a wall, and seeing none, put his hand in front of his face.
"Now hit my hand as hard as you can..."