The Mystery of ELIZA's Teachability

The ELIZA code has a whole "teaching" section, in the sense of the user teaching ELIZA new patterns and responses on the fly. This is actually explicitly described on the very first page of Weizenbaums' 1966 CACM paper, and is (of course) the whole reason that the program was named ELIZA: "Its name was chosen to emphasize that it may be incrementally improved by its users, since its language abilities may be continually improved by a "teacher". Like the Eliza of Pygmalion fame, it can be made to appear even more civilized, the relation of appearance to reality, however, remaining in the domain of the playwright.". However, so far as we know, user teahability did not make it into any subsequent clone, and so this important feature was lost to history. (One immediate question is what to make of the phrase: "...the relation of appearance to reality, however, remaining in the domain of the playwright." ?!)