EVERY TIME we see one of those reports on the work of people who have been teaching chimpanzees or other apes to communicate through human sign language, we feel not only the wonderment appropriate to the subject but some uncertainty about where it's all headed. Last week the annual meeting of the American Association for the Advancement of Science gave us a clue: it's headed for the Dairy Queen.

In addition to hearing a report on how some chimpanzees with training in sign language are beginning to pass the language on to other chimps (pretty amazing, but read on), the scientists were told of the progress of a 7-year-old orangutan that has been learning sign language at a university in Tennessee. According to this report, the ape used sign language to ask to be taken for a car ride. It took along money that it had earned for keeping its room clean -- and it gave the driver directions to the Dairy Queen, a well-known source of soft ice cream, where an orangutan's money is apparently as good as the next ape's.

You might think that with this the animal has achieved about all it can hope for and will make no further progress. To believe so would be to underestimate the ingenuity of both apes and humans. Next year, we predict, the annual meeting of the American Association for the Advancement of Science will hear a report on an 8-year-old orangutan at a university in Tennessee that has learned the following sentences in sign language:

"I'm ready to to go for my ride now. May I have my money? . . . No, I haven't really cleaned it yet. I mean I sort of started, but I was watching cartoons, but I'm going to do it this afternoon, really, I am, as soon as we get back. . . . But I want to go on my ride now. . . . Please, Pleeease. Pl. . . . I'll hold my breath. . . . I'll -- Oh, we can go? Thank you. . . . Okay, you drive down to Second Street and take a right, then left at the third stoplight, then your first left after the Exxon station and it's two blocks -- Dairy Queen's on the right."

It is possible the orangutan will also have learned by then to say: "I'm tired of vanilla."