An elderly couple in their nineties are both having problems remembering
things. They decide to go to the doctor for a checkup. The doctor tells
them that they're physically okay but they might want to start writing 
things down to help them remember. Later that night, while watching TV, the
old man gets up from his chair.
 
His wife asks, "Where are you going?"

"To the kitchen," he replies.

"Will you get me a bowl of ice cream?"

"Sure."

"Don't you think you should write it down so you can remember it?" she asks.

"No, I can remember it."

"Well, I'd like some strawberries on top, too. You'd better write it down
because you know you'll forget it."

He says, "I can remember that: You want a bowl of ice cream with strawberries!"

"I'd also like whipped cream. I'm certain you'll forget that, so you'd
better write it down!" she retorts.

Irritated, he says, "I don't need to write it down, I can remember it!  
Leave me alone: Ice cream with strawberries and whipped cream – I’ve got
it, for goodness sake!"

Then he grumbles his way into the kitchen. After twenty minutes the old man
returns from the kitchen and hands his wife a plate of bacon and eggs.

She stares at the plate for a moment and then asks, "Where's my toast?"