| Corrective feedback(CF)refers to teachers’ response to learners’ errors,which plays a crucial role in second language acquisition(SLA).Since the 1980 s,most studies on the effectiveness of corrective feedback have been exclusively concerned with the lexical,grammatic,and pragmatic aspects of language.Little research has been conducted on English vowel pronunciation learning,especially English diphthong contrasts.Moreover,previous research has been focusing on whether CF is effective and which type of CF is more effective,while the relationship between the effectiveness and the target structure was always ignored.In the classroom setting,it is proven that explicit corrective feedback(explicit correction and metalinguistic feedback)only takes a small portion(15%)i n second language teaching(Lyster & Ranta,1997).Therefore,the present study employs recasts and clarification requests,two different kinds of implicit CF,to investigate whether the input-providing and output-providing corrective feedback could facilitate the perception and production of English diphthong contrasts and which is more effective.The study also detects the difference between Mandarin-speaking junior high school students’ pronunciation of the target structures and native speakers’,in order to give some implications to the practical English speech learning and teaching.The specific research questions are as follows.1)What is the difference between Chinese junior high school students and English native speakers in producing the English diphthong contrasts (?)?2)Do recasts and clarification requests make an effect on Chinese middle school students’ perception and production of the English diphthong contrasts (?)?3)Which type of corrective feedback is more effective for the perception and production of the English diphthong contrasts (?)—recasts or clarification requests?Based on the scores in the junior high school entrance examination,fifty-four learners were assigned to three groups : recasts group(9 males and 9 females),clarification requests group(9 males and 9 females)and control group(10 males and8 females),exposed to form-focused instruction of four weeks in total.Four FFI activities including English Karuta Task,explicit instruction,Information Gap and Guessing Game were embedded into the treatment to enable students to notice and practice the target diphthongs in meaningful discourse.The instructor provided recasts and clarification requests to students in each of the two experimental groups in response to their mispronunciation of (?)and (?).The perception was measured using a two-alternative forced-choice identification task,while students’ pronunciation performance was elicited using controlled and spontaneous production tests,after which the recordings were assessed by both acoustic analysis and listener judgment.The independent-sample T test,the three-way ANOVA and the analysis of covariance(ANCOVA)were conducted in SPSS(version 26.0)to analyze the obtained data,namely the F1,F2 values of the diphthongs and transition section on the onset,1/4,1/2,3/4,offset positions,the total and transitional duration time,the ROC values of F2 during the transition,the rating grades on students’ production and the accuracy of students’ perception.According to the statistical comparisons,the major findings of the research are as follows.1)There is a significant difference in the diphthong production between Chinese junior high school students and native speakers.The F1 and F2 values of the students are generally higher than those of native speakers,indicating that students put the tongue higher and more advanced when pronouncing.Meanwhile,the total duration of the target diphthongs produced by students is generally longer than that of native speakers,but the duration of the transitional session is significantly shorter than that of native speakers,indicating that the gliding from the former vowel to the latter one was inadequately performed by Chinese students.2)Both recasts and clarification requests can improve junior high school students’ production of the English diphthong contrasts (?) and (?).By comparing raters’ evaluation of students’ production in the pretest and posttest,it can be seen that students made significant progress in pronouncing all the four diphthongs(p =.000)after instruction,and the improvement of the experimental group is significantly greater than that of the control group(p =.000).In terms of perception,the accuracy significantly improved from pretest to delayed posttest(p =.000),with no significant difference between the experimental group and the control group(p=.414),indicating the effect of CF on the perception remains unclear.3)The effectiveness of the two types of CF on production was not the same when applied to different diphthongs.Recasts play a more effective role in helping students improve the pronunciation of the unfamiliar diphthongs (?) and (?),while clarification requests performed better in assisting students to produce the familiar diphthongs (?) more accurately.And students can make great improvements in the production of (?) no matter with recasts or clarification requests.There was no significant difference between the effectiveness of recasts and clarification requests on developing students’ perception ability.In a word,the results indicated that the positive effect of recasts and clarification requests on improving Mandarin-speaking students’ production and perception of the English diphthong contrasts (?) and (?)-(?) in the context of FFI,while which of the two CF is more significant depending on the relationship between the structure being targeted and the nature of the corrective feedback being selected.The present study confirms the effectiveness of CF in L2 speech teaching and compares the effectiveness of different types of CF in acquiring target structures that differs in nature,which provides a more comprehensive framework for the mechanism of corrective feedback and enriches the practical research of L2 speech teaching of English diphthongs. |
