We've barely started to see what minds must do to comprehend the simplest children's tales. Let's look again at the beginning of our party story.
Mary was invited to Jack's party.
How marvelous that sentence is! How much it says in just six words! Two characters are introduced and quickly cast in clear-cut roles. We learn that there will be a party soon, with Jack as the host and Mary a guest — provided she accepts the invitation. We also learn that this setting is established in the past.
Those six short words tell even more. We can expect the story to focus on Mary's activities rather than Jack's — because Mary is the first word that attracts our attention. But to accomplish that, the narrator had to use a clever grammar-tactic. Normally, an English-language sentence begins with a phrase that describes the Actor responsible for some action, and we usually represent this with a simple Trans-frame.
JACK INVIT — ed MARY Donor action verb Recipient In this active verb form of sentence-frame, the verb is sandwiched between two nouns; the first describes a Donor and the second describes a Recipient. However, if our storyteller actually used the active form of sentence-frame, it would tend to mislead the listener into expecting Jack to be the central character of the story — if only because he is mentioned first. Fortunately, English grammar provides an alternative sentence-frame in which the Recipient is mentioned first — and which never mentions the Donor at all!
MARY was INVIT — ed Recipient was verb — ed.
How does the understanding listener detect this passive verb sentence-frame? Some language-agent has to notice the way the verb is sandwiched between was and -ed. As soon as this special subframe is recognized, the language-agency will reassign the first noun, Mary, not to the Donor terminal, but to the Recipient terminal — and thus Mary is represented as receiving the invitation. Why don't we need to say who the donor is? Because in this case the listener can assume it by default. Specifically, the expression Jack's party evokes a party-invitation frame, and in such situations it is typical for the host — or the host's parents — to invite the party guests. By thus arousing familiar frames, we can say a great deal in a very few words.