六级冲刺练习：阅读（77）

　　What the teacher needs to know is how to connect up a system. And how to load and run programs. Once these skills have been acquired the much more important topic of the evaluation of. computer-based teaching materials can be addressed.

　　The Unintelligent Machine

　　Over the past 20 years the amount of computing power available for a given sum of money has approximately doubled every two years, and it looks as if this trend will continue in the foreseeable future. On the other hand, the fundamental logical design of computers is much the same as at the beginning of this period. The revolution has been one of scale and cost rather than a change in the kinds of things which computers can do. One might have expected therefore that by now we would know the best way in which computers can be used to help with the educational process.

　　In the early sixties, programmed learning was looked on as the pathway to mechanize the learning process. But teaching machines of the time were inflexible and unresponsive. It was soon recognized that computers provide a much higher level of interaction with the student. Responses need not be restricted to multiple-choice button pushing, but can involve the recognition of words or numbers related to the context of the subject.

　　In order to present information and questions to the student and to provide for appropriate branching, depending on the responses, some form of programming language is required. COURSEWRITER and later PILOT are author languages which allow someone without technical knowledge of computing to prepare programs of this kind. Text and graphics can be displayed, responses analyzed, and appropriate action taken.

　　A tool such as this might seem to put considerable power in the hands of the teacher and yet such systems are hardly used at all in our schools. One reason is that the preparation of course material using an author language is, like that for videodisc systems, a very time-consuming business. A figure of 20 to 100 hours of preparation is quoted for each hour of student time at the computer. Such an investment is only worthwhile if the material can be used by a large number of students, and that assumes that the necessary resources in time and hardware are actually available.

　　There is a more fundamental reason for lack of progress in computer-based tutorial systems and this relates to the fundamental lack of intelligence on the part of the computer. It is easy to generate drill and practice exercises which test a students ability to produce response. It is quite another matter to provide useful advice if the response is wrong. The human teacher has a mental model of the student and can make a reasonable estimate of why a particular wrong answer has been produced. The longer the teacher has been in contact with that student the better he or she is able to offer constructive advice. The kind of system discussed above has no such model of the student on which to make decisions, nor does it have access to the large body of subject knowledge which is held by the human teacher. Its responses therefore must be stereotyped and unintelligent.