Memory Loss

Three old ladies are sitting in a diner, chatting about various things.

One lady says, "You know, I'm getting really forgetful. This morning, I was standing at the top of the stairs, and I couldn't remember whether I had just come up or was about to go down."

The second lady says, "You think that's bad? The other day, I was sitting on the edge of my bed and I couldn't remember whether I was going to sleep or had just woken up!"

The third lady smiles smugly, "Well, my memory i s just as good as it's always been, knock on wood," she says as she raps on the table. Then with a startled look on her face, she asks, "Who's there?"