An anecdote shared by Isaac Asimov on himself.  Referring to his auto-mechanic . . .

He had a habit of telling me jokes whenever he saw me.

One time he raised his head from under the automobile hood to say: “Doc, a deaf-and-mute guy went into a hardware store to ask for some nails. He put two fingers together on the counter and made hammering motions with the other hand.

“The clerk brought him a hammer. He shook his head and pointed to the two fingers he was hammering. The clerk brought him nails. He picked out the sizes he wanted, and left. Well, doc, the next guy who came in was a blind man. He wanted scissors. How do you suppose he asked for them?”

Indulgently, I lifted my right hand and made scissoring motions with my first two fingers.

Whereupon my auto-repair man laughed raucously and said, “Why, you dumb jerk, he used his voice and asked for them.”

Then he said smugly, “I’ve been trying that on all my customers today.” “Did you catch many?” I asked. “Quite a few,” he said, “but I knew for sure I’d catch you.”

“Why is that?” I asked. “Because you’re so goddamned educated, doc, I knew you couldn’t be very smart.”