What happens when a child reads a story that begins like this?
Mary was invited to Jack's party. She wondered if he would like a kite.
If you asked what that kite was for, most people would answer that it must be a birthday present for Jack. How amazing it is that every normal person can make such complicated inferences so rapidly — considering that the idea of a gift was never mentioned at all! Could any machine do such remarkable things? Consider all the other assumptions and conclusions that almost everyone will make:
The party is a birthday party. Jack and Mary are children. She is Mary. He is Jack.
She is considering giving Jack a kite. She wonders if he would like the kite.
We call these understandings common sense. They're made so swiftly that they're often ready in our minds before a sentence is complete! But how is this done? In order to realize that the kite is a present, one has to use such knowledge as that parties involve presents, that presents for children are usually toys, and that kites are appropriate toys to be given as presents. None of this is mentioned in the story itself. How do we bring together all that scattered knowledge so quickly? Here's what I think must happen. Somehow the words Mary was invited to Jack's party arouses a party- invitation frame in the reader's mind — and attached to the terminals of that frame are certain memories of various concerns. Who is the host? Who will attend? What present should I bring? What clothing shall I wear? Each of those concerns, in turn, is represented by a frame to whose terminals are already attached, as default assignments, the most usual solutions to that particular kind of problem.
Such knowledge comes from previous experience. I was raised in a culture in which an invitation to a party carries the obligation to arrive well dressed and to bring a birthday present. Accordingly, when I read or hear that Mary was invited to a party, I attribute to Mary the same sorts of subjective reactions and concerns that I would have in such a situation. Therefore, although the story never mentions clothes or gifts at all, to expect their possible involvement seems only simple common sense. But though it is common, it is not simple. The next few sections speculate about how story understanding works.