General studies classify feedback into three forms, oral feedback and written feedback, form feedback and content feedback, direct feedback and indirect feedback.

Oral feedback and written feedback are pided according to the form. Teachers’ oral feedback refers to face-to-face verbal feedback between students and teachers through discussion of article modification, mainly in the form of writing session. Due to the timely feedback, oral feedback targets better on error correction and is very easy to train students themselves to develop the modification capacity. Teachers’ written feedback refers to reviewing articles and providing revisions by sign. Students modify and review the article through written feedback in order to effectively improve their writing skills. In practical teaching, these two kinds of feedback are combined together by many teachers.

In writing research areas, form feedback includes the overall format of articles, the grammatical form of articles, etc. Content feedback mainly involves the specific topic of the article, emotions, facts and expression. The experiment of Kepner (1991) shows that the writing skills of students who have accepted content feedback are improved more greatly than those who have received form feedback. The studies of Hedgcock and Lefkowtz (1994) show that students are more inclined to accept the content feedback of teachers, feedback that focus on form but ignores the content will reduce students’ writing interest and is not conducive to improve students’ writing skills.

A domestic research has done by Yang Jingqing (1996) among sophomores of non-English majors, which prove that both content and form feedback can improve students’ writing, and the effect of the two ways of feedback is not so different. Numerous studies of subsequent scholars also suggest that the combination of content and form feedback helps more to improve modification skills of students’ writing than simple content or form feedback. According to Long’s study (2007), when the teacher gives marks on grammatical errors of an essay, he gives direct feedback; if a teacher just points out the problems, then he is providing indirect feedback.

Lalande (1982) finds that indirect feedback is more beneficial than direct feedback for student’s long-term progress. Similarly, Ferris (1997) believes direct feedback may lead to misunderstanding of the meaning that students truly want to express and impose their own ideas to the students. Although scholars tend to think that indirect feedback is better than direct feedback, Lee (2004) finds that 76 percent of the students want teachers to give direct feedback to errors, while only 22% of students want teachers to give direct feedback on some errors. 

2.2 Previous studies on writing feedback

Feedback mentioned above is paid more and more attention to. 

    Lewis’s book (2007) Giving Feedback in Language Classes concluded the main purpose of feedback in her book in the following aspects: 

    (1) Feedback provides teachers and students with information.

    (2) Feedback provides students with learning proposal.

    (3) Feedback provides students with language input.

    (4) Feedback is a form of motivation to learn.

(5) Feedback can guide students to develop independent learning habits.

There have been two different perspectives around teachers’ feedback in English writing. In the early 1980s and 1990s, researchers began to question the effectiveness and proficiency of teachers’ feedback on students’ writing.