Washback is the degree to which an instructional or influence assessment all appearance of the learning process ,students' motivation ,study habits, educators' curriculum ,and materials decisions, etc. It can be both negative and positive. Another method Hughes (2003: 55) recommends to promote positive washback is through the use of criterion-referenced tests. In this way, students will understand that if they can complete tasks “at the criteria level, then they will be successful on the test” (ibid). This may promote students learning to perform tasks rather than competing to get a high score in comparison to their peers
negative washback effects of "teaching to the test" may very well outweigh whatever positive washback the high-stakes nature of the test may create in terms of extrinsic motivation to study, since it is rational for students who are motivated by the need to succeed on this test to invest their time and money in test-oriented study materials or programs rather than a more holistic language-learning approach.